Backup & Recovery Concept on RHEL / CentOS 5.X&6.X

    
Backup:-

                 

                 Data Backup is the physical copying of data files to a removable  storage device that allows the data to be stored in another location.  When needed, an individual data file or an entire set of data files,  can be restored to a computer system.

USERS OF  BACKUP & RECOVERY:

    1)To copy data to alternate media 

    2)To prevent data loss 

     

     Note: Only administrators can backup the data

Types of data:

      I)System generated data

      II)User generated data

Types of backup:

      1)Full backup

      2)Incremental backup

      3)Differential backup

 1)Full backup :   complete backup of entire system

2)Incremental backup:  It includes all files that were changed since last backup. It always smaller than differential backup.

3)Differential backup:  It includes all the files that were changed since last full backup. As time increases since the last full backup the size of differential backup increases.

Commands for backup:

     1)tar (tape archieve)

     2)cpio (copy input/output)

     3)dump

1) tar:

#tar <options> <destination> <source>

Note:destination must be in .tar extension

options:

-c=create

-v=verbose

-f=file

-t=table of content

-x=extract to

-w=interactive

-z=zip

To take backup

#tar -cvf <path> <file name> <source>

ex:tar -cvf passwd.tar /etc/passwd 

To list the content of tar file

#tar -tvf <path> <file name>

ex:tar -tvf passwd.tar 

To extract content of file

#tar -xvf <path> <file name>

ex:tar -xvf passwd.tar

To take backup along with zip

#tar -cvzf <path> <file name>

Note:file name must be with an extension of .tar.gz

example : #tar -cvzf passwd.tar.gz /etc/passwd

To extract zip file

#tar -xvzf <path> <file name>

example : #tar -xvzf passwd.tar.gz

2) cpio(copy input/output):

Backup using cpio:

#ls <options> | cpio -ov > <file name>

example:ls -l | cpio -ov > sun

To extract:

#cpio -iv <file name>

example:cpio -iv sun

3) dump  : 

Backup using dump:

#dump -Ouf <device> <file name>

example:dump -Ouf /media/<pendrive> sun

To extract:

#restore -f <path>

example:restore -f sun

Remote backup:

#rsync -avz <source> -e ssh <destination IP>:<directory>

example:rsync -avz mahesh -e ssh 192.168.1.20:/root/mahesh

#scp -r <source> <destination IP>:<directory>

example:scp -r mahesh  192.168.1.20:/root/mahesh