Monday, August 19

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


                 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:

#tar <options> <destination> <source>
Note:destination must be in .tar extension
-t=table of content
-x=extract to

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

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

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