Category: Linux System Administration

Using UDev to configure ASM disks

Published on by Advait4 Comments

This is a small article on using UDev on RHEL 7. I have a virtual box with RHEL 7 and I am configuring ASM diskgroups.

Before we configure ASM diskgroups, we need to have disks/partitions available at OS level and those should be recognized by ASM. Oracle provides a utility called ASMLib which can be installed and used very easily to configure disk/partitions at OS level.

ASMLib stamps the header of partitions/disk at OS level with Oracle format making them easily detected by ASM instance doing disk discovery. You can go through ASMLib installation, configuration and usage in an article write by my friend Anand Prakash – https://aprakash.wordpress.com/2016/05/19/oracle-asmlib

In this article we will focus on using UDev for setting up ASM disks.

Let’s start with some information on UDev

What is Udev?

Udev is the device manager for the Linux 2.6 kernel that creates/removes device nodes in the /dev directory dynamically. It is the successor of devfs and hotplug. It runs in userspace and the user can change device names using Udev rules.

Why Do We Need It ?

In the older kernels, the /dev directory contained statics device files. But with dynamic device creation, device nodes for only those devices which are actually present in the system are created. Let us see the disadvantages of the static /dev directory, which led to the development of Udev.

Problems Identifying the Exact Hardware Device for a Device Node in /dev

The kernel will assign a major/minor number pair when it detects a hardware device while booting the system. Let us consider two hard disks. The connection/alignment is in such a way that one is connected as a master and the other, as a slave. The Linux system will call them, /dev/hda and /dev/hdb. Now, if we interchange the disks the device name will change. This makes it difficult to identify the correct device that is related to the available static device node. The condition gets worse when there are a bunch of hard disks connected to the system.

Udev provides a persistent device naming system through the /dev directory, making it easier to identify the device.

Huge Number of Device Nodes in /dev

In the static model of device node creation, no method was available to identify the hardware devices actually present in the system. So, device nodes were created for all the devices that Linux was known to support at the time. The huge mess of device nodes in /dev made it difficult to identify the devices actually present in the system.

Not Enough Major/Minor Number Pairs

The number of static device nodes to be included increased a lot in recent times and the 8-bit scheme, that was used, proved to be insufficient for handling all the devices. As a result the major/minor number pairs started running out.

Working of Udev

The Udev daemon listens to the netlink socket that the kernel uses for communicating with user space applications. The kernel will send a bunch of data through the netlink socket when a device is added to, or removed from a system. The Udev daemon catches all this data and will do the rest, i.e., device node creation, module loading etc.

Kernel Device Event Management

  • When bootup is initialized, the /dev directory is mounted in tmpfs.
  • After that, Udev will copy the static device nodes from /lib/udev/devices to the /dev directory.
  • The Udev daemon then runs and collects uevents from the kernel, for all the devices connected to the system.
  • The Udev daemon will parse the uevent data and it will match the data with the rules specified in /etc/udev/rules.d.
  • It will create the device nodes and symbolic links for the devices as specified in the rules.
    The Udev daemon reads the rules from /etc/udev/rules.d/*.rules and stores them in the memory.
  • Udev will receive an inotify event, if any rules were changed. It will read the changes and will update the memory.

Let’s start by creating disks at OS level. VirtualBox has commands which creates block devices at OS level.

Using Udev to configure disks

Step 1) Creating Block devices at OS level

I am creating 4 disks, each of 10GB using following command

VBoxManage createhd --filename asm1.vdi --size 10240 --format VDI --variant Fixed
VBoxManage createhd --filename asm2.vdi --size 10240 --format VDI --variant Fixed
VBoxManage createhd --filename asm3.vdi --size 10240 --format VDI --variant Fixed
VBoxManage createhd --filename asm4.vdi --size 10240 --format VDI --variant Fixed

Step 2) Attaching the disk to the correct storage

VBoxManage storageattach 12102 --storagectl "SATA" --port 1 --device 0 --type hdd --medium asm1.vdi --mtype shareable
VBoxManage storageattach 12102 --storagectl "SATA" --port 2 --device 0 --type hdd --medium asm2.vdi --mtype shareable
VBoxManage storageattach 12102 --storagectl "SATA" --port 3 --device 0 --type hdd --medium asm3.vdi --mtype shareable
VBoxManage storageattach 12102 --storagectl "SATA" --port 4 --device 0 --type hdd --medium asm4.vdi --mtype shareable

12102 is the name of virtual machine. You can see the virtual machine name as shown in below screen shot.

vbox

Step 3) (optional) Making disk sharable

This is optional step and is required only if you are using ASM cluster. In that case ASM disks should be made shareable as should be attached to all machines in cluster. You can use following commands to make the disks sharable

VBoxManage modifyhd asm1.vdi --type shareable
VBoxManage modifyhd asm2.vdi --type shareable
VBoxManage modifyhd asm3.vdi --type shareable
VBoxManage modifyhd asm4.vdi --type shareable

Step 4) Check if the disks are now shown in your virtual box

Following screen shot shows that disks are now added to correct virtual machine

vbox copy

Also, after you login to virtual box, you should be able to see new devices under /dev directory

[root@advait ~]# ls -l /dev/sd*
brw-rw---- 1 root disk 8, 0 Jul 18 05:36 /dev/sda
brw-rw---- 1 root disk 8, 1 Jul 18 05:36 /dev/sda1
brw-rw---- 1 root disk 8, 2 Jul 18 05:36 /dev/sda2
brw-rw---- 1 root disk 8, 16 Jul 18 05:36 /dev/sdb
brw-rw---- 1 root disk 8, 32 Jul 18 05:36 /dev/sdc
brw-rw---- 1 root disk 8, 48 Jul 18 05:36 /dev/sdd
brw-rw---- 1 root disk 8, 64 Jul 18 05:36 /dev/sde

/dev/sda, /dev/sda1 and /dev/sda2 are partitions of main device used for virtual box.
/dev/sdb, /dev/sdc, /dev/sdd and /dev/sde are the devices we added to virtual box as above.

Step 5) Format the new devices and create partitions

You need to create new partitions using fdisk utility. I am showing the command for one partition, you can repeate the same for remaining partitions.

[root@advait ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0xbda01838.

Command (m for help): n
Partition type:
 p primary (0 primary, 0 extended, 4 free)
 e extended
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-20971519, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-20971519, default 20971519): 
Using default value 20971519
Partition 1 of type Linux and of size 10 GiB is set

Command (m for help): p

Disk /dev/sdb: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xbda01838

Device Boot Start End Blocks Id System
/dev/sdb1 2048 20971519 10484736 83 Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

This will create single partition for each of the devices.

[root@advait ~]# ls -rlt /dev/sd*1
brw-rw---- 1 root disk 8, 1 Jul 18 05:36 /dev/sda1
brw-rw---- 1 root disk 8, 17 Jul 18 05:40 /dev/sdb1
brw-rw---- 1 root disk 8, 33 Jul 18 05:40 /dev/sdc1
brw-rw---- 1 root disk 8, 49 Jul 18 05:41 /dev/sdd1
brw-rw---- 1 root disk 8, 65 Jul 18 05:41 /dev/sde1

Step 5) Configure UDev rules

So before creating UDev rule, we need to understand what exactly we want to do. We want to create alias for each of the disk that we created at OS level so that it is always identified the same way, regardless of the device name Linux assigns it. This can be done by recognizing each device based on some unique IDs and assining the alias to that device. UDev can do just that.

Each disk has a unique SCSI ID. We can use this unique ID to recognize the disk and assign the required alias to that disk.
We can get unique SCSI_ID using following command

[root@advait ~]# /usr/lib/udev/scsi_id -g -u -d /dev/sdb1
1ATA_VBOX_HARDDISK_VB544d069c-abd3901e

scsi_id command is located in /usr/lib/udev/ directory on RHEL 7. But in previous release this used to be in /sbin/ location.

Like wise we can find SCSI_ID for each disk that we added.

Rules are defined in “/etc/udev/rules.d” directory. Udev reads these rules and apply them to devices listed in /dev directory.

Rules looks like below

KERNEL=="sd?1", SUBSYSTEM=="block", -
PROGRAM=="/usr/lib/udev/scsi_id -g -u -d /dev/$parent", -
RESULT=="1ATA_VBOX_HARDDISK_VB88ee7178-f28aa887", -
SYMLINK+="asm-disk1", OWNER="oracle", GROUP="dba", MODE="0660"

Following is the explanation of each parameter

  • KERNEL==”sd?1″ – This matches the kernel name of the device. In our case all our partitions are having names as sd?1 (sdb1, sdc1 etc). So this match key matches the kernel name of the devices
  • SUBSYSTEM==”block” – This match key matches the subsystem of the devices. SUBSYSTEM could be block, scsi, usb etc. We have all block devices.
  • PROGRAM==”/usr/lib/udev/scsi_id -g -u -d /dev/$parent” – This will get the unique SCSI_ID for the device searched by first 2 match parameters (KERNEL and SUBSYSTEM)
  • RESULT==”1ATA_VBOX_HARDDISK_VB544d069c-abd3901e” – This will match the output of PROGRAM command with RESULT. If the result matches, then further action will be taken
  • SYMLINK+=”asm-disk1″ – This parameter is part of action key. If PROGRAM output matches RESULT, then a SYMLINK will be created, which is named asm-disk1 and will be pointing to the device in question.
  • OWNER=”oracle” – This parameter is also part of action. This will change the ownership of device to oracle user
  • GROUP=”dba” – This parameter changes the group of device to dba group
  • MODE=”0660″ – This changes the permission of device file to 0660

So above rule means that the device pointing to the partition “sd*1” on the disk with the SCSI ID of “1ATA_VBOX_HARDDISK_VB88ee7178-f28aa887” will always be referred with symlink “/dev/asm-disk1” pointing to the device, regardless of the letter “?” Linux assigns when the device is discovered. In addition, the device will have the correct ownership and permissions for ASM.

We can create such rule for each of the device or if number of devices are huge, we can use wildcard and matching patterns to create more intelligent rules to search and take required actions.

I have created following rules and we can create a new rule file /etc/udev/rules.d/99-oracle-asm-disks.rules and put following rules, one for each device

KERNEL=="sd?1", SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d /dev/$parent", RESULT=="1ATA_VBOX_HARDDISK_VB544d069c-abd3901e", SYMLINK+="asm-disk1", OWNER="oracle", GROUP="dba", MODE="0660"
KERNEL=="sd?1", SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d /dev/$parent", RESULT=="1ATA_VBOX_HARDDISK_VB9a630cc5-d9697727", SYMLINK+="asm-disk2", OWNER="oracle", GROUP="dba", MODE="0660"
KERNEL=="sd?1", SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d /dev/$parent", RESULT=="1ATA_VBOX_HARDDISK_VB446fdf92-8640efff", SYMLINK+="asm-disk3", OWNER="oracle", GROUP="dba", MODE="0660"
KERNEL=="sd?1", SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d /dev/$parent", RESULT=="1ATA_VBOX_HARDDISK_VB3a71b4f2-8c603b78", SYMLINK+="asm-disk4", OWNER="oracle", GROUP="dba", MODE="0660"

Step 6) Load updated block device partition tables

You can use partprobe to load the partition tables for block devices

/sbin/partprobe /dev/sdb1
/sbin/partprobe /dev/sdc1
/sbin/partprobe /dev/sdd1
/sbin/partprobe /dev/sde1

Step 7) Test the rules

This is optional step to check if the rules are working as expected. You can run following commands to test the rules

udevadm test /block/sdb/sdb1
udevadm test /block/sdb/sdc1
udevadm test /block/sdb/sdd1
udevadm test /block/sdb/sde1

The output for one of the above command looks like following

calling: test
version 219
This program is for debugging only, it does not run any program
specified by a RUN key. It may show incorrect results, because
some values may be different, or not available at a simulation run.

=== trie on-disk ===
tool version: 219
file size: 6984832 bytes
header size 80 bytes
strings 1805856 bytes
nodes 5178896 bytes
Load module index
Created link configuration context.
timestamp of '/etc/udev/rules.d' changed
Reading rules file: /usr/lib/udev/rules.d/10-dm.rules
Reading rules file: /usr/lib/udev/rules.d/100-balloon.rules
Reading rules file: /usr/lib/udev/rules.d/13-dm-disk.rules
Reading rules file: /usr/lib/udev/rules.d/40-redhat.rules
Reading rules file: /usr/lib/udev/rules.d/42-usb-hid-pm.rules
Reading rules file: /usr/lib/udev/rules.d/50-udev-default.rules
Reading rules file: /usr/lib/udev/rules.d/60-alias-kmsg.rules
Reading rules file: /usr/lib/udev/rules.d/60-cdrom_id.rules
Reading rules file: /usr/lib/udev/rules.d/60-drm.rules
Reading rules file: /usr/lib/udev/rules.d/60-keyboard.rules
Reading rules file: /usr/lib/udev/rules.d/60-net.rules
Reading rules file: /usr/lib/udev/rules.d/60-persistent-alsa.rules
Reading rules file: /usr/lib/udev/rules.d/60-persistent-input.rules
Reading rules file: /usr/lib/udev/rules.d/60-persistent-serial.rules
Reading rules file: /usr/lib/udev/rules.d/60-persistent-storage-tape.rules
Reading rules file: /usr/lib/udev/rules.d/60-persistent-storage.rules
Reading rules file: /usr/lib/udev/rules.d/60-persistent-v4l.rules
Reading rules file: /usr/lib/udev/rules.d/60-raw.rules
Reading rules file: /usr/lib/udev/rules.d/61-accelerometer.rules
Reading rules file: /usr/lib/udev/rules.d/64-btrfs.rules
Reading rules file: /usr/lib/udev/rules.d/70-mouse.rules
Reading rules file: /usr/lib/udev/rules.d/70-power-switch.rules
Reading rules file: /usr/lib/udev/rules.d/70-touchpad.rules
Reading rules file: /usr/lib/udev/rules.d/70-uaccess.rules
Reading rules file: /usr/lib/udev/rules.d/71-biosdevname.rules
Reading rules file: /usr/lib/udev/rules.d/71-seat.rules
Reading rules file: /usr/lib/udev/rules.d/73-idrac.rules
Reading rules file: /usr/lib/udev/rules.d/73-seat-late.rules
Reading rules file: /usr/lib/udev/rules.d/75-net-description.rules
Reading rules file: /usr/lib/udev/rules.d/75-probe_mtd.rules
Reading rules file: /usr/lib/udev/rules.d/75-tty-description.rules
Reading rules file: /usr/lib/udev/rules.d/78-sound-card.rules
Reading rules file: /usr/lib/udev/rules.d/80-drivers.rules
Reading rules file: /usr/lib/udev/rules.d/80-net-name-slot.rules
Reading rules file: /usr/lib/udev/rules.d/80-net-setup-link.rules
Reading rules file: /usr/lib/udev/rules.d/81-kvm-rhel.rules
Reading rules file: /usr/lib/udev/rules.d/85-nm-unmanaged.rules
Reading rules file: /usr/lib/udev/rules.d/90-alsa-tools-firmware.rules
Reading rules file: /usr/lib/udev/rules.d/90-iprutils.rules
Reading rules file: /usr/lib/udev/rules.d/90-vconsole.rules
Reading rules file: /usr/lib/udev/rules.d/91-drm-modeset.rules
Reading rules file: /usr/lib/udev/rules.d/95-dm-notify.rules
Reading rules file: /usr/lib/udev/rules.d/95-udev-late.rules
Reading rules file: /usr/lib/udev/rules.d/98-kexec.rules
Reading rules file: /usr/lib/udev/rules.d/98-rdma.rules
Reading rules file: /etc/udev/rules.d/99-oracle-asm-disks.rules
Reading rules file: /usr/lib/udev/rules.d/99-systemd.rules
rules contain 24576 bytes tokens (2048 * 12 bytes), 12216 bytes strings
1803 strings (22584 bytes), 1184 de-duplicated (10988 bytes), 620 trie nodes used
GROUP 6 /usr/lib/udev/rules.d/50-udev-default.rules:52
LINK 'disk/by-id/ata-VBOX_HARDDISK_VB544d069c-abd3901e-part1' /usr/lib/udev/rules.d/60-persistent-storage.rules:43
IMPORT builtin 'blkid' /usr/lib/udev/rules.d/60-persistent-storage.rules:72
probe /dev/sdb1 raid offset=0
PROGRAM '/usr/lib/udev/scsi_id -g -u -d /dev/sdb' /etc/udev/rules.d/99-oracle-asm-disks.rules:1
starting '/usr/lib/udev/scsi_id -g -u -d /dev/sdb'
'/usr/lib/udev/scsi_id -g -u -d /dev/sdb'(out) '1ATA_VBOX_HARDDISK_VB544d069c-abd3901e'
'/usr/lib/udev/scsi_id -g -u -d /dev/sdb' [10122] exit with return code 0
OWNER 54321 /etc/udev/rules.d/99-oracle-asm-disks.rules:1
GROUP 54322 /etc/udev/rules.d/99-oracle-asm-disks.rules:1
MODE 0660 /etc/udev/rules.d/99-oracle-asm-disks.rules:1
LINK 'asm-disk1' /etc/udev/rules.d/99-oracle-asm-disks.rules:1
PROGRAM '/usr/lib/udev/scsi_id -g -u -d /dev/sdb' /etc/udev/rules.d/99-oracle-asm-disks.rules:2
starting '/usr/lib/udev/scsi_id -g -u -d /dev/sdb'
'/usr/lib/udev/scsi_id -g -u -d /dev/sdb'(out) '1ATA_VBOX_HARDDISK_VB544d069c-abd3901e'
'/usr/lib/udev/scsi_id -g -u -d /dev/sdb' [10123] exit with return code 0
PROGRAM '/usr/lib/udev/scsi_id -g -u -d /dev/sdb' /etc/udev/rules.d/99-oracle-asm-disks.rules:3
starting '/usr/lib/udev/scsi_id -g -u -d /dev/sdb'
'/usr/lib/udev/scsi_id -g -u -d /dev/sdb'(out) '1ATA_VBOX_HARDDISK_VB544d069c-abd3901e'
'/usr/lib/udev/scsi_id -g -u -d /dev/sdb' [10124] exit with return code 0
PROGRAM '/usr/lib/udev/scsi_id -g -u -d /dev/sdb' /etc/udev/rules.d/99-oracle-asm-disks.rules:4
starting '/usr/lib/udev/scsi_id -g -u -d /dev/sdb'
'/usr/lib/udev/scsi_id -g -u -d /dev/sdb'(out) '1ATA_VBOX_HARDDISK_VB544d069c-abd3901e'
'/usr/lib/udev/scsi_id -g -u -d /dev/sdb' [10125] exit with return code 0
handling device node '/dev/sdb1', devnum=b8:17, mode=0660, uid=54321, gid=54322
preserve permissions /dev/sdb1, 060660, uid=54321, gid=54322
preserve already existing symlink '/dev/block/8:17' to '../sdb1'
found 'b8:17' claiming '/run/udev/links/\x2fasm-disk1'
creating link '/dev/asm-disk1' to '/dev/sdb1'
preserve already existing symlink '/dev/asm-disk1' to 'sdb1'
found 'b8:17' claiming '/run/udev/links/\x2fdisk\x2fby-id\x2fata-VBOX_HARDDISK_VB544d069c-abd3901e-part1'
creating link '/dev/disk/by-id/ata-VBOX_HARDDISK_VB544d069c-abd3901e-part1' to '/dev/sdb1'
preserve already existing symlink '/dev/disk/by-id/ata-VBOX_HARDDISK_VB544d069c-abd3901e-part1' to '../../sdb1'
created db file '/run/udev/data/b8:17' for '/block/sdb/sdb1'
ACTION=add
DEVLINKS=/dev/asm-disk1 /dev/disk/by-id/ata-VBOX_HARDDISK_VB544d069c-abd3901e-part1
DEVNAME=/dev/sdb1
DEVPATH=/block/sdb/sdb1
DEVTYPE=partition
ID_ATA=1
ID_ATA_FEATURE_SET_PM=1
ID_ATA_FEATURE_SET_PM_ENABLED=1
ID_ATA_SATA=1
ID_ATA_SATA_SIGNAL_RATE_GEN2=1
ID_ATA_WRITE_CACHE=1
ID_ATA_WRITE_CACHE_ENABLED=1
ID_BUS=ata
ID_MODEL=VBOX_HARDDISK
ID_MODEL_ENC=VBOX\x20HARDDISK\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20\x20
ID_PART_ENTRY_DISK=8:16
ID_PART_ENTRY_NUMBER=1
ID_PART_ENTRY_OFFSET=2048
ID_PART_ENTRY_SCHEME=dos
ID_PART_ENTRY_SIZE=20969472
ID_PART_ENTRY_TYPE=0x83
ID_PART_TABLE_TYPE=dos
ID_REVISION=1.0
ID_SERIAL=VBOX_HARDDISK_VB544d069c-abd3901e
ID_SERIAL_SHORT=VB544d069c-abd3901e
ID_TYPE=disk
MAJOR=8
MINOR=17
SUBSYSTEM=block
TAGS=:systemd:
USEC_INITIALIZED=404668
Unload module index
Unloaded link configuration context.

Step 8) Reload rules of udev

Use following command to reload the rules

udevadm control --reload-rules

Check if the required symlinks and other actions are performed on the devices or not

[root@advait ~]# ls -rlt /dev/asm*
lrwxrwxrwx 1 root root 4 Jul 18 06:20 /dev/asm-disk2 -> sdc1
lrwxrwxrwx 1 root root 4 Jul 18 06:20 /dev/asm-disk3 -> sdd1
lrwxrwxrwx 1 root root 4 Jul 18 06:20 /dev/asm-disk4 -> sde1
lrwxrwxrwx 1 root root 4 Jul 18 06:20 /dev/asm-disk1 -> sdb1

Above symlinks are owned by root, but devices will be owned by oracle:dba

[root@advait ~]# ls -rlt /dev/sd?1
brw-rw---- 1 root disk 8, 1 Jul 18 05:36 /dev/sda1
brw-rw---- 1 oracle dba 8, 33 Jul 18 06:20 /dev/sdc1
brw-rw---- 1 oracle dba 8, 49 Jul 18 06:20 /dev/sdd1
brw-rw---- 1 oracle dba 8, 65 Jul 18 06:20 /dev/sde1
brw-rw---- 1 oracle dba 8, 17 Jul 18 06:20 /dev/sdb1

Now ASM can identify the disks as /dev/asm-disk* and these symlinks will persist with host reboot.

Hope this helps !!

References:

https://www.linux.com/news/udev-introduction-device-management-modern-linux-system
http://www.reactivated.net/writing_udev_rules.html

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Logical Volume Manager and Logical Volumes – Linux

Published on by Advait2 Comments

Introduction

This post describes what is LVM (Logical Volume Manager) in Linux and how to create Logical volumes.

LVM is a higher level layer of abstraction then traditional linux disk and partitions. This allows for greater flexibility in allocating storage. Logical volumes can be resized and moved between physical devices easily. Physical devices can be added and removed with relative ease. LVM managed volumes can also have sensible names like “database” or “home” rather then somewhat cryptic “sda” or “hda” device names.

As shown in above figure,

  • Devices are designated as Physical Volume
  • One or more physical volumes are used to create volume group
  • Physical volumes are defined with Physical extents of a fixed size
  • Logical volumes are created on volume group and are composed of physical extents
  • File system may be created on Logical Volume

Creating Logical Volume

Creating Logical volume is a 6 step process

1) Create a partitions of the type Linux LVM. The code for this is 8e. For details about creating partitions check the previous post Creating Partition and Filesystem in Linux.

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         123      987966   8e  Linux LVM
/dev/sdb2             124         246      987997+  8e  Linux LVM
/dev/sdb3             247         369      987997+  8e  Linux LVM
/dev/sdb4             370         652     2273197+   5  Extended
/dev/sdb5             370         492      987966   8e  Linux LVM
/dev/sdb6             493         615      987966   8e  Linux LVM

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

run partprobe command for kernel to read the partition table

[root@localhost ~]# partprobe
Warning: Unable to open /dev/hdc read-write (Read-only file system).  /dev/hdc has been opened read-only.
[root@localhost ~]# cat /proc/partitions
major minor  #blocks  name

8     0   10485760 sda
8     1     104391 sda1
8     2    3068415 sda2
8     3    3068415 sda3
8     4          1 sda4
8     5    1020096 sda5
8     6    1020096 sda6
8     7     514048 sda7
8     8     987966 sda8
8    16    5242880 sdb
8    17     987966 sdb1
8    18     987997 sdb2
8    19     987997 sdb3
8    20          1 sdb4
8    21     987966 sdb5
8    22     987966 sdb6

2) Create a phyical volume out of these partitions

[root@localhost ~]# pvcreate /dev/sdb1
Physical volume “/dev/sdb1” successfully created
[root@localhost ~]# pvcreate /dev/sdb2
Wiping software RAID md superblock on /dev/sdb2
Physical volume “/dev/sdb2” successfully created
[root@localhost ~]# pvcreate /dev/sdb3
Wiping software RAID md superblock on /dev/sdb3
Physical volume “/dev/sdb3” successfully created

3) Create a volume group using these physical volumes

[root@localhost ~]# vgcreate vg0 /dev/sdb1 /dev/sdb2
Volume group “vg0” successfully created

4) Create a logical volume from this volume group

[root@localhost ~]# lvcreate -L 512M -n data vg0
Logical volume “data” created

5) Formatting the logical volume

[root@localhost ~]# mkfs.ext3 /dev/vg0/data
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
131072 inodes, 524288 blocks
26214 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67633152
64 block groups
8192 blocks per group, 8192 fragments per group
2048 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409

Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 21 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

6) Mount the logical volume

[root@localhost ~]# mkdir /vol0
[root@localhost ~]# mount /dev/vg0/data /vol0
[root@localhost ~]# cd /vol0/
[root@localhost vol0]# df -h .
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg0-data  496M   19M  452M   4% /vol0

Hope this helps !!

Simulating the RAID Failure

Published on by AdvaitLeave a comment

This post is about simulating the failure of software RAID. We change the status of hardware partition as failed and simulate the failure.

Here we are using Level 1 raid as explained in by previous post Configuring software RAID (Level 1) on Linux. We are using 2 partitions here /dev/sdb1and /dev/sdb2. We will make /dev/sdb2 fail and then replace that with a new partition /dev/sdb3 of same size.

Status of current RAID can be obtained using

[root@localhost avdeo]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sdb2[1] sdb1[0]
987840 blocks [2/2] [UU]

unused devices: <none>

Simulation of software RAID can be done easily using following 3 steps.

1) Make the device fail.

You can make the device fail using mdadm -f command.

[root@localhost avdeo]# mdadm -f /dev/md0 /dev/sdb2
mdadm: set /dev/sdb2 faulty in /dev/md0

If we check /proc/mdstat we can see that device has been marked as faulty

[root@localhost avdeo]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sdb2[2](F) sdb1[0]
987840 blocks [2/1] [U_]

unused devices: <none>

we can also see the messages in /var/log/messages file

[root@localhost avdeo]# tail -f /var/log/messages
Sep 16 09:04:33 localhost kernel: EXT3-fs: mounted filesystem with ordered data mode.
Sep 16 09:17:05 localhost kernel: raid1: Disk failure on sdb2, disabling device.
Sep 16 09:17:05 localhost kernel:       Operation continuing on 1 devices
Sep 16 09:17:05 localhost kernel: RAID1 conf printout:
Sep 16 09:17:05 localhost kernel:  — wd:1 rd:2
Sep 16 09:17:05 localhost kernel:  disk 0, wo:0, o:1, dev:sdb1
Sep 16 09:17:05 localhost kernel:  disk 1, wo:1, o:0, dev:sdb2
Sep 16 09:17:05 localhost kernel: RAID1 conf printout:
Sep 16 09:17:05 localhost kernel:  — wd:1 rd:2
Sep 16 09:17:05 localhost kernel:  disk 0, wo:0, o:1, dev:sdb1

2) Remove the device from RAID

[root@localhost avdeo]# mdadm –remove /dev/md0 /dev/sdb2
mdadm: hot removed /dev/sdb2

[root@localhost avdeo]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sdb1[0]
987840 blocks [2/1] [U_]

unused devices: <none>

As we can see sdb2 is not seen in /proc/mdstat

Also if we check mdadm –detail command we can see that /dev/sdb2 has been removed.

[root@localhost avdeo]# mdadm –detail /dev/md0
/dev/md0:
Version : 00.90.03
Creation Time : Tue Sep 16 08:59:31 2008
Raid Level : raid1
Array Size : 987840 (964.85 MiB 1011.55 MB)
Device Size : 987840 (964.85 MiB 1011.55 MB)
Raid Devices : 2
Total Devices : 1
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Tue Sep 16 09:19:08 2008
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0

UUID : dcf37c14:179f9a7a:ed1f46c6:a8160267
Events : 0.6

Number   Major   Minor   RaidDevice State
0       8       17        0      active sync   /dev/sdb1
1       0        0        1      removed

3) Add a new device

[root@localhost avdeo]# mdadm –add /dev/md0 /dev/sdb3
mdadm: added /dev/sdb3

Check mdadm –detail

[root@localhost avdeo]# mdadm –detail /dev/md0
/dev/md0:
Version : 00.90.03
Creation Time : Tue Sep 16 08:59:31 2008
Raid Level : raid1
Array Size : 987840 (964.85 MiB 1011.55 MB)
Device Size : 987840 (964.85 MiB 1011.55 MB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Tue Sep 16 09:19:08 2008
State : clean, degraded, recovering
Active Devices : 1
Working Devices : 2
Failed Devices : 0
Spare Devices : 1

Rebuild Status : 34% complete

UUID : dcf37c14:179f9a7a:ed1f46c6:a8160267
Events : 0.6

Number   Major   Minor   RaidDevice State
0       8       17        0      active sync   /dev/sdb1
2       8       19        1      spare rebuilding   /dev/sdb3

Thats it !! we are done.

Hope this helps !!

Configuring software RAID (Level 1) on Linux

Published on by Advait4 Comments

Introduction

This post is about creating a software RAID using the existing partitions. Usually for RAID device we should use different disk. But here since I don’t have that much hardware available, use partitions to demonstrate the software RAID configuration.

There are different level of RAID available. We can create level 0, level 1 and level 5 RAID using software RAID.

Following table gives a brief idea about different RAID level possible by software RAID.

Assuming that each disk is of 10G here we can have

RAID Level Min # Disk Required Effective Storage Technique
Level 0 2 20G Stripping
Level 1 2 10G Mirroring
Level 5 3 20G Stripping with parity
Level 6 6 20G Stripping with multiple parity

Configuring RAID

Following are the simple steps to be done as a system administrator to configure software RAID. I am creating Level 1 RAID here.

Step 1) Creating RAID partitions

RAID partitions are of type fd (Linux RAID Autodetect). Creating 5 partitions of type fd, each of size 1G.

[root@localhost ~]# fdisk /dev/sdb

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot      Start         End      Blocks   Id  System

Command (m for help): n
Command action
e   extended
p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-652, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-652, default 652): +1G

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): L

0  Empty           1e  Hidden W95 FAT1 80  Old Minix       be  Solaris boot
1  FAT12           24  NEC DOS         81  Minix / old Lin bf  Solaris
2  XENIX root      39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-
3  XENIX usr       3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-
4  FAT16 <32M      40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
5  Extended        41  PPC PReP Boot   85  Linux extended  c7  Syrinx
6  FAT16           42  SFS             86  NTFS volume set da  Non-FS data
7  HPFS/NTFS       4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .
8  AIX             4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility
9  AIX bootable    4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt
a  OS/2 Boot Manag 50  OnTrack DM      93  Amoeba          e1  DOS access
b  W95 FAT32       51  OnTrack DM6 Aux 94  Amoeba BBT      e3  DOS R/O
c  W95 FAT32 (LBA) 52  CP/M            9f  BSD/OS          e4  SpeedStor
e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a0  IBM Thinkpad hi eb  BeOS fs
f  W95 Ext’d (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  EFI GPT
10  OPUS            55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/
11  Hidden FAT12    56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b
12  Compaq diagnost 5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor
14  Hidden FAT16 ❤ 61  SpeedStor       a9  NetBSD          f4  SpeedStor
16  Hidden FAT16    63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fd  Linux raid auto
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fe  LANstep
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid ff  BBT
1c  Hidden W95 FAT3 75  PC/IX
Hex code (type L to list codes): fd
Changed system type of partition 1 to fd (Linux raid autodetect)

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         123      987966   fd  Linux raid autodetect

Like wise create 4 more partition

at the end it should look like as shown below

Command (m for help): p

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1         123      987966   fd  Linux raid autodetect
/dev/sdb2             124         246      987997+  fd  Linux raid autodetect
/dev/sdb3             247         369      987997+  fd  Linux raid autodetect
/dev/sdb4             370         652     2273197+   5  Extended
/dev/sdb5             370         492      987966   fd  Linux raid autodetect
/dev/sdb6             493         615      987966   fd  Linux raid autodetect

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

Step 2) Running partprobe

Running partprobe will ask kernel to read the partition table from disk into memory, so that new partition will be in effect.

[root@localhost ~]# partprobe
Warning: Unable to open /dev/hdc read-write (Read-only file system).  /dev/hdc has been opened read-only.
[root@localhost ~]# cat /proc/partitions
major minor  #blocks  name

8     0   10485760 sda
8     1     104391 sda1
8     2    3068415 sda2
8     3    3068415 sda3
8     4          1 sda4
8     5    1020096 sda5
8     6    1020096 sda6
8     7     514048 sda7
8     8     987966 sda8
8    16    5242880 sdb
8    17     987966 sdb1
8    18     987997 sdb2
8    19     987997 sdb3
8    20          1 sdb4
8    21     987966 sdb5
8    22     987966 sdb6

Step 3) Create a RAID device of defined level.

Here we are using /dev/sdb1 and /dev/sdb2 partition to create Level 1 RAID.

[root@localhost ~]# mdadm -C /dev/md0 -a yes -l 1 -n 2 /dev/sdb{1,2}
mdadm: array /dev/md0 started.

Here mdadm is the command to create raid device
-C is the create option
/dev/md0 is the device name
-a yes option is to create a RAID file if it doesnt exists
-l 1 is the RAID level 1 (mirroring)
-n 2 is number of device 2
/dev/sdb{1,2} are the device names (/dev/sdb1, /dev/sdb2)

Step 4) Format the RAID device

Once the RAID device is created, next step is to format the device. We will format for ext3 type.

[root@localhost ~]# mkfs.ext3 /dev/md0
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
123648 inodes, 246960 blocks
12348 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=255852544
8 block groups
32768 blocks per group, 32768 fragments per group
15456 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376

Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 33 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

Step 5) Last step is mounting the file system

[root@localhost ~]# mkdir /raid1
[root@localhost ~]# mount /dev/md0 /raid1
[root@localhost ~]# cd /raid1
[root@localhost raid1]# df -h .
Filesystem            Size  Used Avail Use% Mounted on
/dev/md0              950M   18M  885M   2% /raid1

As we know that RAID 1 is mirroring, so effective disk space is half that of the provided disk. Here we provided 2 disk partitions of 1G each. So the effective disk space is approx 1G.

You can see the details of RAID device using mdadm –detail command as shown below

[root@localhost raid1]# mdadm –detail /dev/md0
/dev/md0:
Version : 00.90.03
Creation Time : Tue Sep 16 08:59:31 2008
Raid Level : raid1
Array Size : 987840 (964.85 MiB 1011.55 MB)
Device Size : 987840 (964.85 MiB 1011.55 MB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Tue Sep 16 09:02:11 2008
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0

UUID : dcf37c14:179f9a7a:ed1f46c6:a8160267
Events : 0.2

Number   Major   Minor   RaidDevice State
0       8       17        0      active sync   /dev/sdb1
1       8       18        1      active sync   /dev/sdb2

Step 6) Adding a RAID device to /etc/fstab

[root@localhost ~]# cat /etc/fstab | grep md
/dev/md0                /raid1                  ext3    defaults        0 0

Next post, we will simulate the failure of one of the RAID disk and try to replace the same.

Hope this helps !!

Cron and Anacron – Linux Scheduling Utility

Published on by Advait7 Comments

Introduction

cron is a scheduling utility used by normal user to schedule recurring events. cron exists for every user. We can place any program of any script which we want to schedule to run periodically in side cron. We can also give the timing information for the script to run.

Placing entry in crontab

We can place the entry in cron using “crontab -e” command. -e arguement is for edit.
Entry in cron tab needs to be plcaed in specific format. Following is the required format.

<Minutes> <Hours> <Day Of Month> <Month> <Day of Week> <Script Name and arguement to scrip>
0-59           0-23        1-31                    1-12        0-7                   <Script Name and arguement to scrip>

Example:

To run script every sunday at 1:00 PM

00  13  * * 0 <Script to be executed>

* indicates all values. So above setting will execute script at 13:00 hours on all days of month and in all months and on sunday. The last 0 indicates sunday. The days of week start from 0 (or 7) which means sunday, 1 means monday etc, 6 means saturday.

To run the script on 10th Day of every 3rd month at 5:30 AM

30 05 10 3,6,9,12 * <script to be executed>

So above setting will run the script on 10th day of 3rd, 6th, 9th and 12th month of year at 5:30 AM.

When ever a user creates a cron a file gets created in /var/spool/cron directory by the name of that user. If you cat this file you will see all the crons setup by that user.

A user can list the cron using crontab -l

Example:

[avdeo@localhost ~]$ crontab -l
00 10 * * * echo “Message” > /dev/null

You can remove the cron using “crontab -r” command.

Crons for root (sysadmin)

When linux is installed, by defauly some crons get installed. These are the system crons. These crons are required by system for carrying out some system maintenance activities. Example, some of the system maintenance activity.

System crons are installed in a file called /etc/crontab

-bash-3.00$ cat /etc/crontab
SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
HOME=/

# run-parts
01 * * * * root run-parts /etc/cron.hourly
02 4 * * * root run-parts /etc/cron.daily
22 4 * * 0 root run-parts /etc/cron.weekly
42 4 1 * * root run-parts /etc/cron.monthly

The format of this file is different then user cron.

Example, if we see the following line

02 4 * * * root run-parts /etc/cron.daily

Here the first 5 values are similar to the normal cron value. The 6th value is the username which will be used to run the comamnd in the seventh field. run-parts is the script present in /usr/bin directory. This script take 1 arguements. In this case the arguement we are passing is /etc/cron.daily.
/etc/cron.daily is the directory which contains several script that needs to be run daily. So any script which needs to be run daily as a root can be put in this directory. Also we have directories like /etc/cron.hourly, /etc/cron.weekly, /etc/cron.monthly etc

So all the scripts in /etc/cron.daily directory will run daily at 4:02 AM.

Anacron

Anacron is another utility that runs the jobs which didnt run because the server was down. For example if there are certain critical jobs which are scheduled to run daily and should never be skipped and suppose that server was down at the time these critical jobs are scheduled in cron to run. Then in such cases cron will not run these script at later point of time when the server comes up. Cron only run the script at specified time. once that time limit is skipped, the programs are run only on next cycle.
Anacron is the utility which can rescue at such situation.

This is how the anacron works:

When the cron runs the run-parts script from /etc/crontab for cron.daily, cron.weekly, cron.monthly, the first command that it runs is 0anacron. This command sets a time stamp in the files present in /var/spool/anacron

-bash-3.00$ ls -lrt /var/spool/anacron/cron*
-rw——-  1 root root 9 Sep  1 04:42 /var/spool/anacron/cron.monthly
-rw——-  1 root root 9 Sep 14 04:33 /var/spool/anacron/cron.weekly
-rw——-  1 root root 9 Sep 15 04:04 /var/spool/anacron/cron.daily

Example if we see the file /var/spool/anacron/cron.daily we see yesterdays time stamp.

[root@localhost ]# cat /var/spool/anacron/cron.daily
20080916

This is the time stamp when the command in /etc/cron.daily was last run.

On boot up, anacron command runs and check these files present in /var/spool/anacron/ directory and check the time stamp.

Anacron has its own config file /etc/anacrontab. This file tells which script should be run at what time interval. The config file looks as shown below.

-bash-3.00$ cat /etc/anacrontab
# /etc/anacrontab: configuration file for anacron

# See anacron(8) and anacrontab(5) for details.

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root

1       65      cron.daily              run-parts /etc/cron.daily
7       70      cron.weekly             run-parts /etc/cron.weekly
30      75      cron.monthly            run-parts /etc/cron.monthly

Here the first column gives the frequency with which the script in /etc/cron* directories should run.
If the script have not run at this frequency (as decided by last time stamp in /vatr/spool/anacron/cron* file) then anacron will wait for few minutes (as given by the second column in /etc/anacrontab file above) and then run the commands, thus ensuring that if a server was down during the time that cron should have run these commands, they are, nonethless, run.

Hope this helps !!

Creating Partition and Filesystem in Linux

Published on by Advait1 Comment

Introduction

This post describes how to create a partitons in linux and use it. Creating a new partition for use is a 4 step process.

  1. You identify a disk and create a partition using fdisk
  2. You create a file system on that disk and assign a label
  3. You create an entry in /etc/fstab to make partition persistant accrose reboot
  4. You mount the partition for access to the user.

Lets start with creating a partition from a disk.

Creating Partition and filesystem

In my system I have /dev/sda as primary device and following are the different partitions

[root@10.176.87.179]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2             2.9G  350M  2.4G  13% /
/dev/sda7             487M   18M  444M   4% /home
/dev/sda6             965M   18M  898M   2% /data
/dev/sda3             2.9G  1.7G  1.1G  62% /usr
/dev/sda1              99M   11M   83M  12% /boot
tmpfs                 252M     0  252M   0% /dev/shm
/dev/hdc              2.8G  2.8G     0 100% /cdrom

The total size for all these partitions (except cdrom) comes to 7.5G. Addition to that I have 1G swap partition created on /dev/sda5

[root@10.176.87.179]# swapon -s
Filename                                Type            Size    Used    Priority
/dev/sda5                               partition       1020088 0       -1

So that makes it 8.5G. Total size of /dev/sda is 10G. This leaves 1.5G free for creating another partition.

1) create a partition using fdisk

fdisk -l will give the list of existing partition

[root@10.176.87.179]# fdisk -l

Disk /dev/sda: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14         395     3068415   83  Linux
/dev/sda3             396         777     3068415   83  Linux
/dev/sda4             778        1305     4241160    5  Extended
/dev/sda5             778         904     1020096   82  Linux swap / Solaris
/dev/sda6             905        1031     1020096   83  Linux
/dev/sda7            1032        1095      514048+  83  Linux

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdb doesn’t contain a valid partition table

For creating a partition, we can use fdisk followed by device name.

[root@10.176.87.179]# fdisk /dev/sda

The number of cylinders for this disk is set to 1305.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)

Command (m for help): n
First cylinder (1096-1305, default 1096):
Using default value 1096
Last cylinder or +size or +sizeM or +sizeK (1096-1305, default 1305): +1G

Command (m for help): p

Disk /dev/sda: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      104391   83  Linux
/dev/sda2              14         395     3068415   83  Linux
/dev/sda3             396         777     3068415   83  Linux
/dev/sda4             778        1305     4241160    5  Extended
/dev/sda5             778         904     1020096   82  Linux swap / Solaris
/dev/sda6             905        1031     1020096   83  Linux
/dev/sda7            1032        1095      514048+  83  Linux
/dev/sda8            1096        1218      987966   83  Linux

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table.
The new table will be used at the next reboot.
Syncing disks.

The above step creates a raw partition. Here it prompted for

Command (m for help):
and we entered “n”. “n” here means new partition. Then it asked for starting cylinder. By default it takes the cylinder in continuation. Else if we leave some cylinders in between that slot will be empty and we wont be able to use those unless if we want to create the partition of exact that size. So better to accept the default and create a partition in continuous cylinders.

Next input it ask is the end cylinder number. Usually its hard to calculate the number of cylinders depending on the size of slot we need. So we can directly enter the size of slot as +1G or +500M. Here G, M and K can be used representing GB, MB and KB. Remember to use + at the start.

Once these inputs are given, we can use “p” to print the partition list and see if its going to create correct partition. Please note that till now nothing has happened. We are just checking our setting by typing “p”. After checking when we type “w” that time its going to start creating a partition. So we can backoff any time using “quit” until we type “w”.

2) create a file system on that partition and assign a label

For creating a partition, following command is used.

mkfs.ext3 <options> <partition>

Following are the main and important options

-b <number> -> This represent the block size to be used.
-i <number> -> This represent the block/inode ratio.

inode is a pointer to each and every file in linux. For every file there is an inode. usually its not a good idea to give same number of inodes as number of blocks.

Example:

Partition size = 1000M
block size = 2K
Number of blocks = 500K (1000M/2K)

For each file created, however small it is, its going to use atleast 1 block. And for each file we need 1 inode value.

Now if there are 500K blocks, its not a good idea to give 500K as inode value. Because we are not going to have 500K files. If you thing about it usually in a normal file system some of the file will be larger then 2K (block size). In that case single file will occupy more number of blocks and but still number of inode used for that file will be only 1.

Another disadvantage of giving more number of inode values is that, it will take more space for storing those many values in inode table.

For more options on mkfs.ext3 command, see the man pages.

Lets try creating a file system.

[root@10.176.87.179]# mkfs.ext3 -b 2048 -i 4096 /dev/sda8
mke2fs 1.39 (29-May-2006)
Could not stat /dev/sda8 — No such file or directory

The device apparently does not exist; did you specify it correctly?

OK. Now we got this error. The reason we got this error is because, even though we created a partition, our kernel does not know about it.

When we create a partition, an entry goes in the partition table of that device. This partition table is maintained in the 1st sector of that device. During booting kernel reads the partition table and loads it in memory.

So does that mean that we need to reboot out system? Apperantly reboot can solve our problem, but we can solve the same without reboot as well. We have a command called partprob which will ask kernel to read the partition table on the device and load into memory. Doing that, kernel will know about new partition.

You can list the current partition which kernel is aware of using /proc/partitions file. /proc is a virtual file system in memory. This contains all the information which kernel is aware of and which is used by kernel.

[root@10.176.87.179]# cat /proc/partitions
major minor  #blocks  name

8     0   10485760 sda
8     1     104391 sda1
8     2    3068415 sda2
8     3    3068415 sda3
8     4          1 sda4
8     5    1020096 sda5
8     6    1020096 sda6
8     7     514048 sda7
8    16    5242880 sdb

So we can see here that partition sda8 is not loaded in memory. Now lets run partprobe command.

[root@10.176.87.179]# partprobe

Now if we see /proc/partitions we see sda8

[root@10.176.87.179]# cat /proc/partitions
major minor  #blocks  name

8     0   10485760 sda
8     1     104391 sda1
8     2    3068415 sda2
8     3    3068415 sda3
8     4          1 sda4
8     5    1020096 sda5
8     6    1020096 sda6
8     7     514048 sda7
8     8     987966 sda8
8    16    5242880 sdb

Now try the mkfs.ext3 command.

[root@10.176.87.179]# mkfs.ext3 -b 2048 -i 4096 -L /oracle /dev/sda8
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=2048 (log=1)
Fragment size=2048 (log=1)
247008 inodes, 493982 blocks
24699 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=506462208
31 block groups
16384 blocks per group, 16384 fragments per group
7968 inodes per group
Superblock backups stored on blocks:
16384, 49152, 81920, 114688, 147456, 409600, 442368

Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 30 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

So it has created the required file system.
-L is used to give label to that partition. This is not a mandatory option.

3) Create an entry in /etc/fstab to make partition persistant accrose reboot

Now to make this partition get mounted automatically when the system reboots, we should make entry in /etc/fstab file. /etc/fstab is the file which kernel reads during booting and mount the file system mentioned in this file.

This file has entry in following format

<device Name>     <Mount Point>     <File system Type>    <Mount Option>    <Dump Frequency>     <File system Check order>

Device Name -> Name of the partition which needs to be mounted
Mount Point -> Directory which is to be used as moint point
File system Type -> Type used for creating file system. ext3 in our case.
Mount Option -> Various options used during mount. Check man page for mkfs command to check various mount options.
Dump Frequency -> 0 – never dump, 1 – daily, 2 – every other day etc. This is a sort of taking  backup.
File System Check order -> Order in which file system is checked while the system boots. 0 – ignore, 1 – always for root etc.

So here is our entry will look like

[root@10.176.87.179]# cat /etc/fstab | grep oracle
LABEL=/oracle           /oracle                 ext3    defaults        0 0

4) mount the partition for access to the user.

[root@10.176.87.179]# mkdir /oracle
[root@10.176.87.179]# mount -a
[root@10.176.87.179]# cd /oracle
[root@10.176.87.179]# df -h .
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda8             935M   24M  863M   3% /oracle

mount -a is going to mount all the devices present in /etc/fstab file. You can also mount /dev/sda8 using following command

[root@10.176.87.179]# mount /dev/sda8 /oracle

hope this helps !!

YUM (Yellow dog Updater, Modifier)

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Introduction

With Redhat Enterprise Linux 5, a new utility has been introduced. This is a work of few programmers from Duke university.

Imagine that we have to apply an rpm and we dont have yum. In that case we will start applying the rpm using “rpm” command and it gives a dependency error saying that some other files and rpm needs to be installed in order to install this main rpm. Then we will search for dependent rpm and try to apply those. What if those dependent rpms gives dependecy error again saying that some more rpms are required. What if this chain grows long? end result is we will end up totally frustrated and will forget which is our main rpm.

To deal with this kind of issue, yum was introduced. The main advantage of yum is the depenency check. Lets see in more details how yum works and what setup is required for yum to work.

Installing YUM

Yum can be installed using following packages

yum-metadata-parser-1.0-8.fc6
yum-updatesd-3.0.1-5.el5
yum-3.0.1-5.el5
yum-security-1.0.4-3.el5
yum-rhn-plugin-0.5.2-3.el5

Once these packages are installed, we need to create repository for using YUM. YUM always use some repository for installing rpm. Repository is a directory containg all rpm packages. When we give install command to yum it checks if the package we are asking him to install is present in the repository or not. If present in repository, it will go ahead with different checks like public key of the rpm is verified in order to check if the rpm file is modified. It also checks and resolves dependencies. Example if an rpm requires other rpm then it will search for other rpm in the existing repositories (there can be more then 1 repository) and list complete dependencies. It will ask confirmation if we want to goahead, if we say yes, it will install all the rpms including dependent rpms.

Creating repository

Creating a repository is a 4 step process. I will give an example for creating a simple repository.

1) Create a directory and place all packages
2) install createrepo package
3) use  createrepo command to create repository
4) Create a .repo file in /etc/yum.repos.d/ location

Before going ahead, its better if we import the public key for rpm packages. In most of your OS, this step must have done before. Hoever you can do this again just to make sure.

[root@station5 Server]# rpm –import /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

1) Create a directory and place all packages

[root@station5 Server]# cd /home/package/
[root@station5 package]# ls
zenity-2.16.0-2.el5.i386.rpm       zlib-1.2.3-3.i386.rpm        zsh-html-4.2.6-1.i386.rpm
zip-2.31-1.2.2.i386.rpm            zlib-devel-1.2.3-3.i386.rpm
zisofs-tools-1.0.6-3.2.2.i386.rpm  zsh-4.2.6-1.i386.rpm

2) install createrepo package

[root@station5 Server]# yum install createrepo-0.4.4-2.fc6.noarch.rpm
Loading “rhnplugin” plugin
Loading “installonlyn” plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up Install Process
Setting up repositories
No Repositories Available to Set Up
Reading repository metadata in from local files
Parsing package install arguments
Examining createrepo-0.4.4-2.fc6.noarch.rpm: createrepo – 0.4.4-2.fc6.noarch
Marking createrepo-0.4.4-2.fc6.noarch.rpm to be installed
Setting up repositories
No Repositories Available to Set Up
Reading repository metadata in from local files
Resolving Dependencies
–> Populating transaction set with selected packages. Please wait.
—> Package createrepo.noarch 0:0.4.4-2.fc6 set to be updated
–> Running transaction check

Dependencies Resolved

=============================================================================
Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
createrepo              noarch     0.4.4-2.fc6      createrepo-0.4.4-2.fc6.noarch.rpm  141 k

Transaction Summary
=============================================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)

Total download size: 141 k
Is this ok [y/N]: y
Downloading Packages:
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing: createrepo                   ######################### [1/1]

Installed: createrepo.noarch 0:0.4.4-2.fc6
Complete!

3) use createrepo command to create repository

[root@station5 package]# createrepo -v /home/package
1/7 – zlib-devel-1.2.3-3.i386.rpm
2/7 – zenity-2.16.0-2.el5.i386.rpm
3/7 – zlib-1.2.3-3.i386.rpm
4/7 – zsh-html-4.2.6-1.i386.rpm
5/7 – zisofs-tools-1.0.6-3.2.2.i386.rpm
6/7 – zip-2.31-1.2.2.i386.rpm
7/7 – zsh-4.2.6-1.i386.rpm

Saving Primary metadata
Saving file lists metadata
Saving other metadata

4) Create a .repo file in /etc/yum.repos.d/ location

you can create a simple file in /etc/yum.repos.d/ location.
Example station5.repo

The content of this file will look as shown below

[root@station5 yum.repos.d]# cat station5.repo
[station5]
name=new
baseurl=file:///home/package
enable=1
gpgcheck=1

where

[station5]  -> is the name of repository
name=new    -> is the description of repository
baseurl=file:///home/package -> This is the location for your repository. If the repository is on local file system, you have to use protocol “file”. You can also use “ftp” or “http” as protocol if repository is present remotely.
enable=1    -> This specify if yum should enable that repo server for installtion or not 1 is for enable and 0 is for disable
gpgcheck=1  -> check the signature of the rpm package before installation

Once above 4 steps are done, lets try to apply a package present in our repository (zsh-html-4.2.6-1.i386.rpm)

[root@station5 ~]# yum install zsh-html
Loading “rhnplugin” plugin
Loading “installonlyn” plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up Install Process
Setting up repositories
Reading repository metadata in from local files
Parsing package install arguments
Resolving Dependencies
–> Populating transaction set with selected packages. Please wait.
—> Downloading header for zsh-html to pack into transaction set.
zsh-html-4.2.6-1.i386.rpm 100% |=========================|  15 kB    00:00
—> Package zsh-html.i386 0:4.2.6-1 set to be updated
–> Running transaction check

Dependencies Resolved

=============================================================================
Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
zsh-html                i386       4.2.6-1          station5          372 k

Transaction Summary
=============================================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)

Total download size: 372 k
Is this ok [y/N]: y
Downloading Packages:
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing: zsh-html                     ######################### [1/1]

Installed: zsh-html.i386 0:4.2.6-1
Complete!

YUM Options

Different options are available in YUM similar to rpm. Following describes frequently used options.

1) To check if package is installed or not

yum list <package_name>

[root@10.176.87.179]# yum list zsh
Loading “installonlyn” plugin
Loading “rhnplugin” plugin
Loading “security” plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up repositories
Reading repository metadata in from local files
Available Packages
zsh.i386                                 4.2.6-1                DVD

here DVD is the name of repository (Since this package is not installed, its giving the location of package). If the patch is installed, it says “Installed”

yum list will give complete list of packages (installed and also available in repository)

2) To list rpms which are not installed and available in

yum list available

3) To list rpms which are installed

yum list installed

4) To install an rpm

[root@station5 yum.repos.d]# yum install telnet-server
Loading “rhnplugin” plugin
Loading “installonlyn” plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up Install Process
Setting up repositories
Reading repository metadata in from local files
Parsing package install arguments
Resolving Dependencies
–> Populating transaction set with selected packages. Please wait.
—> Downloading header for telnet-server to pack into transaction set.
telnet-server-0.17-38.el5 100% |=========================| 8.4 kB    00:00
—> Package telnet-server.i386 1:0.17-38.el5 set to be updated
–> Running transaction check
–> Processing Dependency: xinetd for package: telnet-server
–> Restarting Dependency Resolution with new changes.
–> Populating transaction set with selected packages. Please wait.
—> Downloading header for xinetd to pack into transaction set.
xinetd-2.3.14-10.el5.i386 100% |=========================| 7.7 kB    00:00
—> Package xinetd.i386 2:2.3.14-10.el5 set to be updated
–> Running transaction check

Dependencies Resolved

=============================================================================
Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
telnet-server           i386       1:0.17-38.el5    base               35 k
Installing for dependencies:
xinetd                  i386       2:2.3.14-10.el5  base              124 k

Transaction Summary
=============================================================================
Install      2 Package(s)
Update       0 Package(s)
Remove       0 Package(s)

Total download size: 159 k
Is this ok [y/N]:

So it will ask if we want to install all the dependent packages as well

If we say yes it will install all dependent package as well

5) To remove rpm

yum remove <package_name>

note that we should not put the .rpm extention which installing or removing the rpm. Yum does not accept .rpm extension.

6) To update new version of rpm

yum update <package_name>

7) To search a package

yum search <searchterm>

8) To get information about any package

yum info <package_name>

[root@10.176.87.179]# yum info zsh
Loading “installonlyn” plugin
Loading “rhnplugin” plugin
Loading “security” plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up repositories
Reading repository metadata in from local files
Available Packages
Name   : zsh
Arch   : i386
Version: 4.2.6
Release: 1
Size   : 1.7 M
Repo   : DVD
Summary: A powerful interactive shell
Description:
The zsh shell is a command interpreter usable as an interactive login
shell and as a shell script command processor.  Zsh resembles the ksh
shell (the Korn shell), but includes many enhancements.  Zsh supports
command line editing, built-in spelling correction, programmable
command completion, shell functions (with autoloading), a history
mechanism, and more.

yum accept wild characters as well. Make sure to use single quotes.
Example

[root@10.176.87.179]# yum info ‘*irefo*’
Loading “installonlyn” plugin
Loading “rhnplugin” plugin
Loading “security” plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up repositories
Reading repository metadata in from local files
Installed Packages
Name   : firefox
Arch   : i386
Version: 1.5.0.12
Release: 3.el5
Size   : 37 M
Repo   : installed
Summary: Mozilla Firefox Web browser.

Description:
Mozilla Firefox is an open-source web browser, designed for standards
compliance, performance and portability.

Available Packages
Name   : firefox-devel
Arch   : i386
Version: 1.5.0.12
Release: 3.el5
Size   : 3.1 M
Repo   : DVD
Summary: Development files for Firefox
Description:
Development files for Firefox.  This package exists temporarily.
When xulrunner has reached version 1.0, firefox-devel will be
removed in favor of xulrunner-devel.

9) To check which rpm provides the file

[root@10.176.87.179]# yum whatprovides /bin/bash
Loading “installonlyn” plugin
Loading “rhnplugin” plugin
Loading “security” plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up repositories
Reading repository metadata in from local files

bash.i386                                3.1-16.1               DVD
Matched from:
/bin/bash
filelists.xml.gz          100% |=========================| 2.2 MB    00:00

bash.i386                                3.1-16.1               DVD
Matched from:
/bin/bash

Hope this helps !!

Linux Patching Utility – RPM (RedHat Package Manager)

Published on by Advait1 Comment

Introduction

This post gives a brief introduction about RPM (RedHat Package Manager).

rpm is a command line utility installed when the linux OS is installed. rpm exe is located in /bin

rpm executable is installed as a part of rpm-4.4.2-47.el5.i386.rpm package.

Following are the various options with rpm command.

rpm main options

rpm -i -> Install the package. If the package is present it wont install and will say “nothing to do”, even if we are trying to install a higher version of package. If the package is not present it will install the same.

If you use -v and -h with -i option rpm gives “preety” output. Example

[root@station5 Server]# rpm -i zsh-4.2.6-1.i386.rpm

[root@station5 Server]# rpm -ivh zsh-html-4.2.6-1.i386.rpm
warning: zsh-html-4.2.6-1.i386.rpm: Header V3 DSA signature: NOKEY, key ID 37017186
Preparing…                ########################################### [100%]
1:zsh-html               ########################################### [100%]

i -> Install
v -> Verbose
h -> Hash (for progress bar)

rpm -U -> Upgrade the package. If a new version of package is present then it will upgrade an existing installed version. If package is not applied before then it will apply. So upgrade works whether or not package is installed in OS.
rpm -F -> Freshen the package. This works only for the packages that are installed. If a new version of some package comes for any of the install package, then freshen will install the latest version. But a new version of package comes which is not yet installed in the OS, the freshen will not instal the latest version.
rpm -e -> Uninstalling a package. -e (erase) will remove a package from your system. The package name must be the installed package name and not the rpm file name. Example: rpm -e zip

RPM support FTP and HTTP. Example
[root@station5 Server]# rpm -ivh ftp://server1.example.com/pub/zsh-html-4.2.6-1.i386.rpm

Installing a new kernel using rpm

Installing a new kernel is different process. Usually as explained above when a new version of package comes, we go for -U option which is upgrade. Now with upgrade what exactly happens is that rpm will remove all the existing files and installed the latest rpm package with latest files, Except for configuration files which are backed up with extension .rpmsave.

Kernel is the core of operating system. So when we install new kernel we are not sure whether it will be stable and will work without any issues. So for installing kernel package we use rpm -i (install option). When rpm sees that its the kernel file we are installing it does not overwrite the existing kernel file instead it will create a new kernel files and a new kernel will be installed without removing the old kernel. It will also update grub.conf file with the details of new kernel and when you reboot the system your new kernel will take effect.

Example: Installing a new kernel

[root@station5 errata]# ls -rlt /boot
total 5142
-rw-r–r– 1 root root 1791572 Oct 11  2007 vmlinuz-2.6.18-53.el5
-rw-r–r– 1 root root  903969 Oct 11  2007 System.map-2.6.18-53.el5
-rw-r–r– 1 root root   64551 Oct 11  2007 config-2.6.18-53.el5
-rw-r–r– 1 root root   87586 Oct 11  2007 symvers-2.6.18-53.el5.gz
drwx—— 2 root root   12288 Aug 25 16:37 lost+found
-rw——- 1 root root 2369794 Aug 25 16:41 initrd-2.6.18-53.el5.img
drwxr-xr-x 2 root root    1024 Aug 25 19:41 grub
[root@station5 errata]#

[root@station5 errata]# rpm -ivh kernel-2.6.18-92.el5.i686.rpm
warning: kernel-2.6.18-92.el5.i686.rpm: Header V3 DSA signature: NOKEY, key ID 37017186
Preparing…                ########################################### [100%]
1:kernel                 ########################################### [100%]
[root@station5 errata]# cd /boot
[root@station5 boot]# ls -lrt
total 10315
-rw-r–r– 1 root root 1791572 Oct 11  2007 vmlinuz-2.6.18-53.el5
-rw-r–r– 1 root root  903969 Oct 11  2007 System.map-2.6.18-53.el5
-rw-r–r– 1 root root   64551 Oct 11  2007 config-2.6.18-53.el5
-rw-r–r– 1 root root   87586 Oct 11  2007 symvers-2.6.18-53.el5.gz
-rw-r–r– 1 root root 1806388 Apr 29 22:56 vmlinuz-2.6.18-92.el5
-rw-r–r– 1 root root  912686 Apr 29 22:56 System.map-2.6.18-92.el5
-rw-r–r– 1 root root   65406 Apr 29 22:56 config-2.6.18-92.el5
-rw-r–r– 1 root root   91734 Apr 29 22:56 symvers-2.6.18-92.el5.gz
drwx—— 2 root root   12288 Aug 25 16:37 lost+found
-rw——- 1 root root 2369794 Aug 25 16:41 initrd-2.6.18-53.el5.img
-rw——- 1 root root 2386531 Aug 25 20:23 initrd-2.6.18-92.el5.img
drwxr-xr-x 2 root root    1024 Aug 25 20:23 grub
[root@station5 boot]#

It will update grub.conf as well

title Red Hat Enterprise Linux Server (2.6.18-92.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-92.el5 ro root=LABEL=/ rhgb quiet
initrd /initrd-2.6.18-92.el5.img
title Oracle OS
root (hd0,0)
kernel /vmlinuz-2.6.18-53.el5 ro root=/dev/sda3 rhgb quiet
initrd /initrd-2.6.18-53.el5.img

The default becomes the upgraded kernel.

You can decide which will be the default kernel using following file

[root@station5 boot]# cat /etc/sysconfig/kernel
# UPDATEDEFAULT specifies if new-kernel-pkg should make
# new kernels the default
UPDATEDEFAULT=yes

# DEFAULTKERNEL specifies the default kernel package type
DEFAULTKERNEL=kernel

If UPDATEDEFAULT parameter is set to “yes” then newly installed kernel becomes default. If this is set to no then newly installed kernel will not be the default.

Other rpm Options

Following are the various usage of rpm command.

1) If a package is installed or not

[root@localhost Server]# rpm -qa zip
zip-2.31-1.2.2

2) A particular file is installed from which package

[root@localhost bluetooth]# rpm -qf /lib/modules/2.6.18-53.el5/kernel/net/bluetooth/bluetooth.ko
kernel-2.6.18-53.el5

3) List of files in a package

[root@localhost bluetooth]# rpm -ql zip
/usr/bin/zip
/usr/bin/zipcloak
/usr/bin/zipnote
/usr/bin/zipsplit
/usr/share/doc/zip-2.31
/usr/share/doc/zip-2.31/BUGS
/usr/share/doc/zip-2.31/CHANGES
/usr/share/doc/zip-2.31/LICENSE
/usr/share/doc/zip-2.31/MANUAL
/usr/share/doc/zip-2.31/README
/usr/share/doc/zip-2.31/TODO
/usr/share/doc/zip-2.31/WHATSNEW
/usr/share/doc/zip-2.31/WHERE
/usr/share/doc/zip-2.31/algorith.txt
/usr/share/man/man1/zip.1.gz

4) Package general information

[root@localhost bluetooth]# rpm -qi zip
Name        : zip                          Relocations: (not relocatable)
Version     : 2.31                              Vendor: Red Hat, Inc.
Release     : 1.2.2                         Build Date: Thu 13 Jul 2006 10:33:56 AM IST
Install Date: Fri 29 Aug 2008 06:24:54 AM IST      Build Host: hs20-bc2-2.build.redhat.com
Group       : Applications/Archiving        Source RPM: zip-2.31-1.2.2.src.rpm
Size        : 302524                           License: distributable
Signature   : DSA/SHA1, Thu 18 Jan 2007 09:58:07 PM IST, Key ID 5326810137017186
Packager    : Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla&gt;
URL         : http://www.info-zip.org/pub/infozip/Zip.html
Summary     : A file compression and packaging utility compatible with PKZIP.
Description :
The zip program is a compression and file packaging utility.  Zip is
analogous to a combination of the UNIX tar and compress commands and
is compatible with PKZIP (a compression and file packaging utility for
MS-DOS systems).

Install the zip package if you need to compress files using the zip
program.

5) Check prerequisits for a package

[root@localhost Server]# rpm -qa zip –requires
libc.so.6
libc.so.6(GLIBC_2.0)
libc.so.6(GLIBC_2.1)
libc.so.6(GLIBC_2.2)
libc.so.6(GLIBC_2.3)
libc.so.6(GLIBC_2.3.4)
libc.so.6(GLIBC_2.4)
rpmlib(CompressedFileNames) <= 3.0.4-1
rpmlib(PayloadFilesHavePrefix) <= 4.0-1
rtld(GNU_HASH)

6) Capability provided by rpm package

[root@localhost Server]# rpm -qa kernel –provides
kernel = 2.6.18
kernel-drm = 4.3.0
kernel-i686 = 2.6.18-53.el5
kernel(rhel5_gfs2_ga) = dc42db4764487d4d1e0e658af7ec2eef3c29d91e
kernel(rhel5_fs_lockd_ga) = 321666a6612cc9aa0ed9208fd0159456c9b1ffe3
kernel(rhel5_drivers_hwmon_ga) = 73ec105e064d9b09c6d44c6584f517b73a7d80ab
kernel(rhel5_net_core_ga) = 5aae342a66dcbcc14a7c1c001624f73a13620809
kernel(rhel5_drivers_net_ga) = f740f67835c214eb69aa8c623cb18a6c2ebcdc12
— output truncated —

7) To see the package revision history. The changes occured till now in that rpm package file

[root@localhost Server]# rpm -qa zip –changelog
* Thu Jul 13 2006 Jesse Keating <jkeating@redhat.com> – 2.31-1.2.2
– rebuild

* Sat Feb 11 2006 Jesse Keating <jkeating@redhat.com> – 2.31-1.2.1
– bump again for double-long bug on ppc(64)

* Wed Feb 08 2006 Jesse Keating <jkeating@redhat.com> – 2.31-1.2
– rebuilt for new gcc4.1 snapshot and glibc changes

— output truncated —

8) To check the scripts that runs upon installation or removal of rpm package

[root@localhost Server]# rpm -qa kernel –scripts
postinstall scriptlet (using /bin/sh):
if [ `uname -i` == “x86_64” -o `uname -i` == “i386” ]; then
if [ -f /etc/sysconfig/kernel ]; then
/bin/sed -i -e ‘s/^DEFAULTKERNEL=kernel-smp$/DEFAULTKERNEL=kernel/’ /etc/sysconfig/kernel || exit $?
fi
fi
/sbin/new-kernel-pkg –package kernel –mkinitrd –depmod –install 2.6.18-53.el5 || exit $?
if [ -x /sbin/weak-modules ]
then
/sbin/weak-modules –add-kernel 2.6.18-53.el5 || exit $?
fi
preuninstall scriptlet (using /bin/sh):
/sbin/new-kernel-pkg –rminitrd –rmmoddep –remove 2.6.18-53.el5 || exit $?
if [ -x /sbin/weak-modules ]
then
/sbin/weak-modules –remove-kernel 2.6.18-53.el5 || exit $?
fi

9) Verifying the installed package.

One can verify the installed package using rpm -V option. Verifying an installed package will compare the file size, permissions, type, owner, MD5 checksum and modified time against RPM database.

[root@localhost Server]# rpm -V zip-2.31-1.2.2.i386
[root@localhost Server]# rpm -V kernel
[root@localhost Server]#

rpm -Va will verify all the installed packages.
Example:
[root@localhost Server]# rpm -Va
S.5….T c /etc/sysconfig/system-config-securitylevel
…….T c /etc/kdump.conf
..5….T c /etc/pki/nssdb/secmod.db
SM5….T c /etc/sysconfig/iptables-config

rpm -Vp <Package_file.rpm> will check the integrity of installed package against rpm file and not with database.

Hope this helps !!

Protecting GRUB file using MD5 Password Encryption

Published on by AdvaitLeave a comment

Some times it becomes neccessary to protect the grub.conf with password in order to prevent any user or other system administrator to edit the grub file during reboot.

Example during boot up after BIOS initialization it executes the grub file and shows the operating system menus. At this point, if we press “e” then it will allow the user to edit the grub file for that OS.

Different OS provides different level of protection to avoid this. In redhat, we have some thing called grub-md5-crypt. Using grub-md5-crypt utility we can protect the grub file from updation by unknown user. Only users who are aware of grub password will be able to edit the grub file during boot as it will ask for password.

Following are the steps to generate md5 envrypted password and to protect grub file.

1) run /sbin/grub-md5-crypt

It will ask for password and confirmation for the same. Once you enter password it will generate a 32 character string which is an encrypted form of your password.

2) Make following entry in /etc/grub.conf just before “title” starts

password –md5 <32 char encrypted string>

3) Reboot the system. This time when it comes to menu, you will see it ask us to press “p” in order to enter the password

and then it gives the option to edit grub file.

Hope this helps !!

Installing Linux on Windows Using VMWare

Published on by Advait2 Comments

Introduction:

This post is about redhat Linux 5 installation done on windows. The installation steps are basically same as installing a Linux on new server booting from a disk, but the only difference been that here I have installed VMWare in windows and created a virtual machine and then installed Linux on top of it, kind of like a virtual operating system.

Uses who wants to install Linux on a new server can skip the VMWare installation part and can proceed with Linux installation given. Others who want to use VMWare can install VMWare first on the base operating system and then proceed with Linux installation.

In this post I am going to show only the redhat linux 5 installation and you can check the VMWare installation from Oracle Base site. Oracle Base has given really good steps to install and configure VMWare for our requirement.

Once VMWare is installed and allocated required RAM and diskspace, you can proceed with following Redhat Linux 5 installation.

Linux Redhat 5 Installation

Users who has installed VMWare can start Virtual Machine and it will automatically pick the CD present in CDROM drive, that should be your 1st CD of installation of Linux or the Linux DVD or you can also use the iso image of DVD and provide that as an input to VMWare.

I have provided iso image as an input to VMWare. Use following step to provide iso image as input.

When you start the VMWare local host you will see the following hardware (shown in below fig) attached to the virtual machine

Double click on CD-ROM and change the connection setting to “Use ISO Image” as shown in below fig

Click on OK and start the virtual machine. Virtual machine will automatically detect your ISO image and show you BOOT prompt. We are now ready to install Linux.

Step 1)

When you see boot prompt, hit enter and this will kick off installation.

Step 2)

After execution of some scripts in the backend you will see a welcome screen as shown below. Click on next

Step 3)

Next screen will ask you about the language. Select the prefered language and click on next.

Step 4)

Next it will ask about the keyboard preferences. Select accordingly and click on next.

Step 5)

After clicking next, it will ask for Installation number. In case you have brought a licence from REDHAT, then you can provide the serial number provided by them. This is going to synch up the licence number along with the complete information about your system in there RHN (Redhat network database). Next time any updates come for this version and if its applicable to you then those updates will automatically get downloaded for you. Else you can skip as well, because this is not a mandatory step.

In case you skip then you will see another message, you need to skip that as well as shown below.

Step 6) Next step will ask you about partitioning of dirve. If you want to customize partitioning then you can select “Create Custom Partition” and click on next.

Step 7) You can create custom partition on next screen. Click on “New”button.

Here you can give with standard partition name or any custom name you want to create. Give the required size and format you want to use. usually by default for normal disk, we use ext3 format, which is an ext2 with journoling enabled. Click on OK. Like this you can create all the required partition. The partitioning screen will look as shown below.

Step 8) This step will ask you about the GRUB loader configuration. In my installation I want to keep it simple as of now, so I am not doing any special configuration for GRUB loader.

Step 9) Next screen will ask about the network setting. If you are connected to network, then DHCP will automatically assign IP address to your host. Optionally you can remove DHCP setting and provide a static IP to your host in some different range. In my setup I am keeping DHCP setting as it is.

Step 10) Step 11 will ask you to select the timezone you want to set for your setup. Select the required time zone. Click on next.

Step 11) Next it will ask for root password. You can set any root password you want and confirm the same. This will be your root password to administer and will have all privileges.

Step 12) Next screen will show you the additional general services that comes with redhat, you can select these if you want. Also it provides you a customization option. If you select customize now radio button as shown below, then next screen will be a customization screen and it will ask what are other applications that you want to install. You can select what ever application program you want to install with this installation. I am going for default option as my requirement doesnt need any of these application.

Step 13) This is the last screen before installation. If you proceed it will start the installation first by formatting the disk partition you have provided. You can still back out at this stage if you want to as nothing has changed till now. But if you proceed, you have no control and its going to format the partition provided by you. Click next and installation starts.

step 14) Installation !!

Approximate time for installation is around 15 mins. If the server configuration is good, it completes in 8 mins (believe me 🙂 )

After installation there are few post install steps like setting the data and time, setting firewall, setting SE Linux setting.

SE Linux is a secured Enterprise linux feature introduced in Linux 5, you can set this value to either disable which will disable this feature or you can set it to Enforcing or Permissive. We will talk about this in my future post.

Once all setup is done, it will ask you to reboot the system and after that you can login as root with your password and access this beautiful open source implementation of operating system.

Hope this helps !!