Remove LVM Partitions in Linux

vi /etc/fstab
remove the present lvm entry.

lvremove /dev/VGdata/LVdata
Do you really want to remove active logical volume LVdata? [y/n]: y
  Logical volume "LVdata" successfully removed

vgremove VGdata
  Volume group "VGdata" successfully removed

pvremove /dev/sdb1
  Labels on physical volume "/dev/sdb1" successfully wiped

fdisk /dev/sdb

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Command (m for help): p

Disk /dev/sdb: 26.8 GB, 26843545600 bytes
64 heads, 32 sectors/track, 25600 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000b6891

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       25600    26214384   8e  Linux LVM

Command (m for help): d
Selected partition 1

Command (m for help): p

Disk /dev/sdb: 26.8 GB, 26843545600 bytes
64 heads, 32 sectors/track, 25600 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000b6891

   Device Boot      Start         End      Blocks   Id  System

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

Calling ioctl() to re-read partition table.
Syncing disks.
You have new mail in /var/spool/mail/root

partprobe
Warning: WARNING: the kernel failed to re-read the partition table on /dev/sda (Device or resource busy).  As a result,

it may not reflect all of your changes until after reboot.

reboot

Broadcast message from arao9aj@mb1utarmiweb01.pearsontc.com
        (/dev/pts/0) at 16:12 ...

The system is going down for reboot NOW!

Ref: http://www.linuxspy.com/1810/how-to-remove-lvm-partitions/

Change the default size of an inode

It is possible to define a non-standard sized inode by using the mke2fs tool with an undocumented option, -I. The size of the inode has to be a power of two and between the size of EXT2_GOOD_OLD_INODE_SIZE (128 bytes) and size of blocks in bytes. One reason for doing this could be that user is going to use extended attributes. Extended attributes are arbitrary name/value pairs used to store system objects like Access Control Lists (ACL). If the size of the inodes is larger than the default size, then sufficiently small attributes can be stored in inode

tune2fs -l /dev/mapper/VGdata-LVdata | grep Inode
Inode count:              1572864
Inodes per group:         8192
Inode blocks per group:   512
Inode size:               256

mke2fs -I 8192 /dev/mapper/VGdata-LVdata
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
1572864 inodes, 6291456 blocks
314572 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
192 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000

Writing inode tables: done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 35 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

tune2fs -l /dev/mapper/VGdata-LVdata | grep Inode
Inode count:              3276800
Inodes per group:         16384
Inode blocks per group:   1024
Inode size:               256

Ref: http://magazine.redhat.com/2007/04/23/how-can-i-change-the-default-size-of-an-inode-when-i-create-an-ext2ext3-filesystem/

Commonly Used Shell Variables

echo $BASH_VERSION --holds the version of this instance of bash
3.2.25(1)-release

echo $HOSTNAME --the name of the your computer
LinuxHost

echo $CDPATH --the search path for the cd command

echo $HISTFILE --the file in which command history is saved
/root/.bash_history

echo $HISTFILESIZE --the maximum number of lines contained in the history file
1000

echo $HISTSIZE --the number of commands to remember in the command history
1000

echo $HOME --the home directory of the current user
/root

echo $IFS --the Internal Field Separator

echo $LANG --used to determine the lang

echo $PATH --the search path for commands
/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

echo $PS1 --shows prompt settings
[\u@\h \W]\$

echo $TMOUT --the default timeout for the read builtin command

echo $TERM --the login terminal type
xterm
export TERM=vt100
export TERM=xterm

echo $SHELL --set path to login shell
/bin/bash

echo $DISPLAY --Set X display name
export DISPLAY=:0.1

export EDITOR=/usr/bin/vim --name of default text editor

Find out built in or an external command

type -a bind
bind is a shell builtin

type -a cat
cat is /bin/cat

type -a awk
awk is /bin/awk
awk is /usr/bin/awk

type -a true
true is a shell builtin
true is /bin/true

type -a select
select is a shell keyword

Basic Command Line Editing

Use the following key combinations to edit and recall commands:

• CTRL + L : Clear the screen.

• CTRL + W : Delete the word starting at cursor.

• CTRL + U : Clear the line i.e. Delete the all words from command line.

• Up and Down arrow keys : Recall commands (see command history).

• Tab : Auto-complete files, directory, command names and much more.

• CTRL + R : Search through previously used commands (see command history)

• CTRL + C : Cancel currently running commands.

• CTRL + T : Swap the last two characters before the cursor.

• ESC + T : Swap the last two words before the cursor.

Find out current shell

To find all of the available shells in your system,

echo $SHELL

/bin/bash

To find out your current shell,

which bash


/bin/bash

ps $$

PID TTY      STAT   TIME COMMAND
29893 pts/0    Ss     0:00 -bash

ps -p $$

PID TTY          TIME CMD
29893 pts/0    00:00:00 bash

Valid login shells

cat /etc/shells

/bin/sh
/bin/bash
/sbin/nologin
/bin/tcsh
/bin/csh
/bin/ksh