tar Tape Backup Command to restore Files and Directories

Using the `tar` command in Red Hat Linux to back up and restore files and directories is straightforward. Here are the steps and examples for creating backups and restoring files:

1. Backing Up Files and Directories

   The tar command creates a single archive file (commonly with .tar, .tar.gz, or .tar.bz2 extensions) from files and directories.

   Basic Backup Command

         tar -cvf backup.tar /path/to/directory
       

   • -c: Create a new archive.
   • -v: Verbose mode, shows progress.
   • -f: Specifies the name of the archive file.
   • /path/to/directory: The files or directories to back up.

   Compress the Backup

   You can compress the archive to save space:

   • Using gzip:

               tar -czvf backup.tar.gz /path/to/directory
             

     Use the -z option for gzip compression.

   • Using bzip2:

               tar -cjvf backup.tar.bz2 /path/to/directory
             

     Use the -j option for bzip2 compression.

   Example

   Backup /home/user/docs to a compressed file named docs_backup.tar.gz:

         tar -czvf docs_backup.tar.gz /home/user/docs
       

2. Restoring Files and Directories

   To extract files from a tar archive:

   Extract from a Non-Compressed Archive

         tar -xvf backup.tar
       

   • -x: Extract files.
   • -v: Verbose mode.
   • -f: Specifies the archive file to extract.

   Extract from a Gzip-Compressed Archive

         tar -xzvf backup.tar.gz
       

   Use the -z option for gzip-compressed files.

   Extract from a Bzip2-Compressed Archive

         tar -xjvf backup.tar.bz2
       

   Use the -j option for bzip2-compressed files.

   Extract to a Specific Location

   You can specify a directory where the files should be restored:

         tar -xvf backup.tar -C /path/to/restore
       

   -C: Change to the specified directory before extracting.

   Example

   Restore the contents of docs_backup.tar.gz to /home/user/restored_docs:

         mkdir -p /home/user/restored_docs
         tar -xzvf docs_backup.tar.gz -C /home/user/restored_docs
       

3. Listing Contents of an Archive

   To view the contents of an archive without extracting it:

         tar -tvf backup.tar
       

   -t: Lists files in the archive.

4. Incremental Backup

   For large backups, you can use incremental backup options by combining tar with the --listed-incremental option:

         tar --listed-incremental=snapshot.file -cvf incremental_backup.tar /path/to/directory
       

5. Verifying the Archive

   To verify the integrity of an archive:

         tar -tvf backup.tar
       

Common Tips:

• Always verify backup archives to ensure their integrity.
• Use absolute paths cautiously to avoid accidentally overwriting files when restoring.
• Regularly automate backups using cron jobs. For example:

crontab -e

Add a line like this for daily backups:

0 2 * * * tar -czvf /backup/backup_$(date +\%F).tar.gz /path/to/directory

The tar command is used to create archives and extract files and directories from tar archives. You can use tar as an expedient and simple method for storing an entire file system. You can then use the tar file as a backup, or you can transfer and extract the file onto another machine. tar is very useful for generating daily backups of critical files (such as a current project) or for archiving data, such as mail for an entire organization.
tar "flattens" files and directories into sequential archives that can go to tape or disk. Linux supports standard commands for tape backup. These include

1. c: Create an archive
2. x: Extract files and file systems from a tar archive
3. z: Use gzip compression
4. f: Specify the file system on which to store the archive

In Red Hat Enterprise Linux (RHEL) 9, creating archives typically involves using tools like `tar`, `gzip`, `bzip2`, or `zip`. These tools support various "verbose options" that allow administrators to view detailed output during the creation of archives. Below are the most important verbose options and their practical usage:
Key Verbose Options for Common Tools

1. tar (Tape Archive)

   The `tar` command is widely used for creating, extracting, and managing archive files.

   • -v (Verbose): Provides detailed output of the files being archived or extracted. This is the most commonly used verbose option.

               tar -cvf archive.tar /path/to/files
             

     Output: Displays the list of files being archived.

   • --verbose: Equivalent to `-v`, but uses the long-form option syntax.

               tar --create --verbose --file=archive.tar /path/to/files
             

   • Commonly Combined Options:
     • - `-cvf`: Create (`c`) an archive, verbose (`v`), and specify the file name (`f`).
     • - `-tvf`: List (`t`) the contents of an archive with verbose output.
2. gzip and bzip2

   These are compression utilities commonly used alongside `tar`.

   • -v (Verbose): Shows the compression process and details about the file being compressed or decompressed.
     • gzip:

                     gzip -v file.txt
                   

       Output: Displays the compression ratio and the resulting file name.

     • bzip2:

                     bzip2 -v file.txt
                   

3. zip

   The `zip` command creates compressed ZIP archives.

   • -v (Verbose): Lists detailed information about the files being added to the archive.

               zip -v archive.zip /path/to/files
             

   • --verbose: Provides detailed output in a long-form syntax.

               zip --verbose archive.zip /path/to/files
             

4. cpio

   The `cpio` command is another archive tool often used with verbose options.

   • -v (Verbose): Lists the files being archived.

               find . | cpio -ov > archive.cpio
             

Practical Scenarios

• Backup Operations: Use verbose options to confirm which files are included in an archive during backups.
• Error Detection: Verbose options make it easier to identify errors or skipped files during the archiving process.
• Archive Inspection: Use -tvf or similar options to inspect the contents of an archive without extracting it.

Examples

1. Create a tar.gz Archive with Verbose Output:

         tar -czvf archive.tar.gz /path/to/files
       

2. Extract a tar.bz2 Archive Verbosely:

         tar -xjvf archive.tar.bz2
       

3. Inspect Contents of a tar File:

         tar -tvf archive.tar
       

Verbose options are critical for ensuring the success of archive operations and verifying their accuracy.

The v option for verbose output is not necessary to create and extract tar archives. However, it is useful as a check to view the set of files acted upon as the archive is generated or extracted. The syntax for the verbose option is the same as that for other tar commands. The default tape drive under Linux is /dev/st0 (first SCSI tape device name). Following paragraph summaries command you need to use control tape drive for backup/restore purpose.

• Linux Tape Backup Example To backup to multiple tape use the following command (backup /home file system):
  

  # tar -clpMzvf /dev/st0 /home
  

  
  To compare tape backup, enter:
  

  # tar -dlpMzvf /dev/st0 /home
  

  
  To restore tape in case of data loss or hard disk failure:
  

  # tar -xlpMzvf /dev/st0 /home 
  

Question: What command do you use to create a compressed tar archive named

/project.tar.gz

that contains the files and subdirectories in the /project directory?
Answer:

tar czf /project.tar.gz /project

or

tar zcf /project.tar.gz /project

The next lesson examines the use of the dump command.