Creating Backups – Part II

Untar a tar file:

  • To uncompress tar file (.tar)

-- # tar xvf filename.tar

  • To uncompress a gzip tar file (.tgz or .tar.gz)

-- # tar xvzf filename.tar.gz

  • To uncompress a bzip2 tar file (.tbz or .tar.bz2)

-- tar xvjf filename.tar.bz2

  • Untar in a specified directory:

-- tar -xvf filename.tar -C /pathtodirectory

meaning of the letters when using untar:

  • x = extract, this indicated an extraction
  • v = verbose (optional) the files with relative locations will be displayed
  • z = bzip2 - zipped
  • f = from/to file

ref above:

More examples:

http

To restore a tar archive, or a single file from the archive (by default tar will restore the file in the current directory), use the "x" flag:

Ex:tar xvf /backup/etc.tar etc/resolv.conf

To restore /home from home.tar:tar xvf /tmp/home.tar

To extract files from files.tar in the /tmp directory:

cd /tmp ; tar xvf /tmp/files.tar

To create a tarball called /tmp/home.tar.gz of the /home directory and compress it with gzip:tar cvzf /tmp/home.tar.gz /home

To create a tarball called /tmp/home.tar.bz2 of the /home directory and compress it with bzip2:tar cvjf /tmp/home.tar.bz2 /home

EXAM TIP:Archiving and compression are tasks done together to produce smaller archive files

To list both compressed archives and check which of the two is smaller: ll /tmp/home.tar*

To create a tarball called /tmp/extattr.tar.bz2 of the files in /home directory and include their extended attributes as well as SELinux contents, and compress the archive with bzip2:

Tar cvj –selinux –xattrs –f /tmp/extattr.tar.bz2 /home

Add Files or Directories to tar Archive File:

  • To add files or directories to existing tar archived file, use the "r" (append) option

-- example: To add xyz.txt and directory "var/logs" to existing name.tar archive file:

---> tar -rvfnameoftar.tar xyz.txt

---> tar -rvf nameoftar.tar /var/logs

--> Same thing applies to "tar.gz" and "tar.bz2" archive files

To Check the Size of the tar, tar.gz and tar.bz2 Archive File:

  • tar -czf - nameoftar.tar | wc -c
  • tar -czf - nameoftargz.tar.gz | wc -c
  • tar -czf - nameoffile.tar.bz2 | wc -c

Using “star” archival tool

The star (standard tar) command is an enhanced version of tar.

It supports SELinux security contexts and extended file attributes.

Options for creating, listing, appending, updating and extracting tarballs are the same as the tar command’s

This utility is not installed by default

Example:

  • To create a tarball /tmp/etc.tar containing the entire /etc directory with all extended file attributes and SELinux file contexts, run this command:

-- star cvf /tmp/etc.tar –xattr –H=exustar /etc

  • To list and extract from above, run the following command:

-- star tvf /tmp/etc.tar

-- star xvf /tmp/etc.tar

Labs/Exercise:

-Backup Practice

-Archiving and Extracting with Tar