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The maximum number of PARTITIONS SUPPORTED by LINUX KERNEL is:

• 63 for IDE drives
• 15 for SCSI drives

The maximum number of partitions supported by Linux kernel is:

Separate partitions improve PERFORMANCE by KEEPING DATA TOGETHER which reduces the disk head SEEK.

Separate partitions improve performance by keeping data together which reduces the disk head seek.

• fdisk
• sfdisk
• PARTED (GNU) - An advanced PARTITION manipulation tool (create, copy,resize ETC.)

Reinitializes the KERNEL's in MEMORY COPY of the PARTITION table.

Reinitializes the kernel's in memory copy of the partition table.

The mkfs COMMAND is USED to CREATE the FILESYSTEM.

• mkfs.ext2 / mkfs.ext3>To create ext2/ext3 filesystem
• mkfs.minix> minix filesystem
• mkfs.msdos> MS-DOS filesystem

The mkfs command is used to create the filesystem.

EXT3 FILESYSTEM SUPPORTS JOURNALING, where as EXT2 does not.

ext3 filesystem supports journaling, where as ext2 does not.

• Ordered>Journals only METADATA (This is the DEFAULT)
• Journaled>Journals data as well as metadata
• WRITEBACK> Journal UPDATES are not atomic, but this GIVES better performance.

 Change the /etc/fstab to specify ext3 for DESIRED filesystem(s)
Create the ext3 journal on the EXT2 filesystem(s) as:
# TUNE2FS -j 
If the KERNEL needs to have access to the ext3 module at boot time, create a NEW initial ramdisk as:
# mkinitrd /boot/initrd-.img

 Change the /etc/fstab to specify ext3 for desired filesystem(s)
Create the ext3 journal on the ext2 filesystem(s) as:
# tune2fs -j 
If the kernel needs to have access to the ext3 module at boot time, create a new initial ramdisk as:
# mkinitrd /boot/initrd-.img

MOUNT COMMAND is USED.

Mount command is used.

USE MOUNT COMMAND WITHOUT ARGUMENTS.

Use mount command without arguments.

When mount command is invoked WITHOUT any arguments it REFERES to the /etc/mtab FILESYSTEM.

When mount command is invoked without any arguments it referes to the /etc/mtab filesystem.

The UMOUNT COMMAND is USED.

The umount command is used.

The FUSER COMMAND is USED.

The fuser command is used.

# FUSER -V mnt_point

# fuser -v mnt_point

# FUSER -KM mnt_point

# fuser -km mnt_point

Use the FDISK -L COMMAND to view all the mounted and unmounted filesystems AVAILABLE on your system.

Use the fdisk -l command to view all the mounted and unmounted filesystems available on your system.

Use the DF -k command, which shows only mounted FILESYSTEMS but has the big ADVANTAGE of GIVING you the mount points too.

Use the df -k command, which shows only mounted filesystems but has the big advantage of giving you the mount points too.

With the help of E2LABEL command a filesystem LABEL can be WRITTEN into the superblock of ext2/ext3 filesystem.
 Eg:- #e2label /dev/hda3 datadisk3
Will create a label of datadisk3 on the filesystem on PARTITION /dev/hda3.

With the help of e2label command a filesystem label can be written into the superblock of ext2/ext3 filesystem.
 Eg:- #e2label /dev/hda3 datadisk3
Will create a label of datadisk3 on the filesystem on partition /dev/hda3.

# e2lable /dev/hdb2

# e2lable /dev/hdb2

This file is referenced each time the SYSTEM BOOTS to CREATE the desired filesystem HIERARCHY.

This file is referenced each time the system boots to create the desired filesystem hierarchy.

lsattr COMMAND DISPLAYS FILE ATTRIBUTES

lsattr command displays file attributes

chattr COMMAND CHANGES the FILE ATTRIBUTES.

chattr command changes the file attributes.

SWAP SPACE is SUPPLEMENT to SYSTEM RAM.

Swap space is supplement to system RAM.

Steps involved in SETTING up swap partition:

• CREATE a partition using a partitioning program (fdisk/sfdisk/parted) 
• Set partition id type to 0x82.
• Create the signature on the partition using the mkswap command
• # mkswap -v1 /dev/hdb3
• Add an ENTRY for the swap in /etc/fstab file as:
• /dev/hdb3 swap swap defaults 0 0
• Activate the swap partition using
• # swapon -a
• Check the swap partition STATUS using
• # swapon -s

Steps involved in setting up swap partition:

CREATE a FILE as:

# DD if=/dev/zero of=swapfile bs=512 count=N
(Where N is the file size in KB)
Run the mkswap to create signature
Activate the swap file with swapon command (OR) initialize it in the STARTUP
script /etc/rc.d/rc.local

Create a file as:

# dd if=/dev/zero of=swapfile bs=512 count=N
(Where N is the file size in KB)
Run the mkswap to create signature
Activate the swap file with swapon command (OR) initialize it in the startup
script /etc/rc.d/rc.local

fsck (file SYSTEM CHECK) is used to MAINTAIN file system consistency.

fsck (file system check) is used to maintain file system consistency.

When the system boots, the rc.sysinit SCRIPT runs the fsck on any filesystems marked for checking in /etc/fstab file. If any of these filesystems are markes as dirty or have data in the journal, fsck will attempt to repair them. If it succeeds, the filesystems will be mounted and boot PROCESS continues, else rc.sysinit will run sulogin and will REPORT that fsck NEEDS to be run manually.

When the system boots, the rc.sysinit script runs the fsck on any filesystems marked for checking in /etc/fstab file. If any of these filesystems are markes as dirty or have data in the journal, fsck will attempt to repair them. If it succeeds, the filesystems will be mounted and boot process continues, else rc.sysinit will run sulogin and will report that fsck needs to be run manually.

FSCK is a FRONT END TOOL for E2FSCK.

fsck is a front end tool for e2fsck.

• ORDERED : This is the default and journal only meta-DATA
• Journaled : JOURNALS data and meta-data
• WRITEBACK : Journal UPDATES are not atomic.

This is used to modify the FILESYSTEM ATTRIBUTES (LIKE converting EXT2 to ext3).

This is used to modify the filesystem attributes (Like converting ext2 to ext3).

PROVIDES a dump of FILE SYSTEM information to standard out (Console). Can be redirected to a file.

Provides a dump of file system information to standard out (Console). Can be redirected to a file.

This utility is used to to examine and DEBUG an ext2 filesystem. This can also be used to manually VERIFY the INODE integrity and an AID to recover DATA.

This utility is used to to examine and debug an ext2 filesystem. This can also be used to manually verify the inode integrity and an aid to recover data.

This can be used to change the SIZE of an EXT2 or EXT3 filesystem.

This can be used to change the size of an ext2 or ext3 filesystem.

EXT3 for RHEL 5 and ext4 for RHEL 6.

Ext3 for RHEL 5 and ext4 for RHEL 6.

EXT3

• Maximum individual file size can be from 16 GB to 2 TB
• Overall ext3 file system size can be from 2 TB to 32 TB

Ext4

• Maximum individual file size can be from 16 GB to 16 TB
• Overall maximum ext4 file system size is 1 EB (exabyte). 1 EB = 1024 PB (petabyte). 1 PB = 1024 TB (terabyte).

Ext3

Ext4

kudzu

kudzu

SWAP partition is a feature used in Linux which uses the space allocated to it from the PHYSICAL hard drive and is utilized by te system when RAM MEMORY goes full.

• AMOUNT of RAM in the System RECOMMENDED Amount of Swap Space
• 4GB of RAM or less a minimum of 2GB of swap space
• 4GB to 16GB of RAM a minimum of 4GB of swap space
• 16GB to 64GB of RAM a minimum of 8GB of swap space
• 64GB to 256GB of RAM a minimum of 16GB of swap space
• 256GB to 512GB of RAM a minimum of 32GB of swap space

Swap partition is a feature used in Linux which uses the space allocated to it from the physical hard drive and is utilized by te system when RAM memory goes full.

lvextend -L +1G /dev/VolGroup/LogVol1

This will EXTEND the partition size by +1 GB

resize2fs /dev/VolGroup/LogVol1

lvextend -L +1G /dev/VolGroup/LogVol1

This will extend the partition size by +1 GB

resize2fs /dev/VolGroup/LogVol1

FDISK -L

fdisk -l

mount

mount

It contains a list of all the mounted DIRECTORIES or PARTITIONS on the SYSTEM.

It contains a list of all the mounted directories or partitions on the system.

<P>sysctl -p

sysctl -p

Read only for the first TIME but once you CHANGE it to read write then from NEXT time onward it will be read write.

Read only for the first time but once you change it to read write then from next time onward it will be read write.

BOOT into single user MODE and make the NECESSARY corrections inside FSTAB

Boot into single user mode and make the necessary corrections inside fstab

• The 5TH column tells the DUMP information if WHETHER the partition has to be backed up. It it is "0" the filesystem will be ignored
• The 6th column tells the order in which fsck command would CHECK the filesystem on boot. If it is "0" then fsck won't check the filesystem

lvdisplay

lvdisplay

NFS SHARING is DONE between LINUX to Linux where SAMBA sharing can be done between Linux-Linux and Linux-windows

NFS sharing is done between linux to Linux where Samba sharing can be done between Linux-Linux and Linux-windows

No USER permission which is a SYSTEM ACCOUNT in all the MACHINES having normal user level privileges unless no_root_squash or any other permission specification is not provided on the SHARE.

No user permission which is a system account in all the machines having normal user level privileges unless no_root_squash or any other permission specification is not provided on the share.

sysctl -a

sysctl -a

set

set