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.

    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)

1) tar:

Note:destination must be in .tar extension
-t=table of content
-x=extract to

To take backup

#tar -cvf
ex:tar -cvf passwd.tar /etc/passwd 

To list the content of tar file
#tar -tvf
ex:tar -tvf passwd.tar 

To extract content of file

#tar -xvf
ex:tar -xvf passwd.tar

To take backup along with zip

#tar -cvzf

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
example : #tar -xvzf passwd.tar.gz

2) cpio(copy input/output):

Backup using cpio:

#ls | cpio -ov >
example:ls -l | cpio -ov > sun

To extract:

#cpio -iv
example:cpio -iv sun

3) dump  : 

Backup using dump:
#dump -Ouf
example:dump -Ouf /media/ sun
To extract:
#restore -f
example:restore -f sun

Remote backup:

#rsync -avz -e ssh :
example:rsync -avz mahesh -e ssh

#scp -r :
example:scp -r mahesh

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