Archive and Compression in RHEL 7

 One of the oldest and most common commands for creating and working with backup
archives  is the tar command.

With tar, users can gather large sets of files  into a  single file (archive). The archive can  be
compressed using gzip, bzip2, or xz compression.

Operate the  tar command 
To use the  tar command ,  one of the three following actions is req uired:
- c  (create an archive)
- t  (list the contents of an  archive)
- x  (extract an archive)

Commonly used options are: 
- f  file  name  (file name of the archive to operate on)
- v  (verbosity; useful to see which files get  added to or extracted from the archive)
- p  Preserve the permissions of files and directories when extracting an archive,
without subtracting the umask.

Step 1 : Create a copy of /etc directory

[root@rhel7 ~]# cp -r /etc /home/sirat/etc
[root@rhel7 ~]# du -sh /home/sirat/etc/
34M     /home/sirat/etc/

Step 2: tar archive of etc directory 

[root@rhel7 sirat]# tar -cf etc.tar etc
[root@rhel7 sirat]# du -sh *
34M     etc
30M     etc.tar
8.0K    test
[root@rhel7 sirat]#

Note Here after executing size reduce 4 MB

List contents of a tar archive 

[root@rhel7 sirat]#  tar  tf  /root/etc . tar
etc/
etc/fstab
etc/crypttab
etc/mtab
etc/yum/yum-cron.conf
etc/dhcp/
.

.

.

Step 3: Extract archive of etc.tar to extract directory and check the size also

[root@rhel7 extract]# tar -xf /home/sirat/etc.tar

[root@rhel7 extract]# cd ../

[root@rhel7 sirat]# du -sh *

34M     etc

30M     etc.tar

34M     extract

8.0K    test

[root@rhel7 sirat]#

Step 4: Compressed tar archive file

[root@rhel7 sirat]# tar -czf etc.tar.gz etc              [ gzip compression ] 
[root@rhel7 sirat]# tar -xzf etc.tar.gz etc              [ gzip un compression ] 
[root@rhel7 sirat]# tar -cjf etc.tar.bz2 etc             [ bzip2 compression ] 
[root@rhel7 sirat]# tar -xjf etc.tar.bz2 etc             [ bzip2 un compression ] 
[root@rhel7 sirat]# tar -cJf etc.tar.xz etc               [ xz compression ]
[root@rhel7 sirat]# tar -xJf etc.tar.xz                     [ xz un compression ]

[root@rhel7 sirat]# du -sh *
34M     etc
30M     etc.tar                                      [ tar compression ]
8.3M    etc.tar.gz                                 [ gzip compression ]
7.0M    etc.tar.bz2                               [ bzip2 compression ]
5.7M    etc.tar.xz                                 [ xz compression ] 

8.0K    test

[root@rhel7 sirat]#

To  create a  compressed tar archive, one of the following tar options can be  specified:
.  z  for gzip compression (filename.tar.gz or filename.tgz)
·  j  for bzip2 compression (filename.ta r.bz2)
.  J  for xz compression (filename.tar.xz)

[root@rhel7 sirat]# gzip etc.tar                          [ gzip compression ]
[root@rhel7 sirat]# gunzip etc.tar.gz                 [ gzip un compression ] 
[root@rhel7 sirat]# bzip2 etc.tar                        [ bzip2 compression ] 
[root@rhel7 sirat]# bunzip2 etc.tar.bz2             [ bzip2 un compression ] 

[root@rhel7 sirat]# xz etc.tar                             [ xz compression ] 

[root@rhel7 sirat]# unxz etc.tar.xz                    [ xz un compression ]