Bellevue University CIS 240, Introduction to UNIX Fall Days 2001

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Bellevue UniversityCIS 240, Introduction to
UNIXFall Days 2001

• November 20, 2001
• Backup and Restore

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Backup and Restore

• Planning for Disasters and Everyday Needs
• Backup Media
• Backing Up and Restoring Files and Filesystems
• Backing Up and Restoring the System Filesystems

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Planning for Disasters and Everyday Needs

• Factors to consider
• Backup Strategies
• Storage Considerations

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Factors to consider

• What files need to be backed up?
• Where are these files?
• Who will back up the files?
• Where, when, and under what conditions should
  backups be performed?
• How often do these files change?
• How quickly does an important missing or damaged
  file need to be restored?
• Where will the data be restored?

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Backup Strategies

• Full Backup
• All files are backed up
• Incremental Backup
• Files changed since the last backup are backed up
• Unattended Backups
• Backups are automatically started at a scheduled
  time

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Storage Considerations

• Know where things are
• Make routine restorations easy
• Write-protect backup media
• Environmental considerations
• Handle media properly
• Take security into account

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Backup Media

• Magnetic tape
• Floppy disks
• Removable disks
• Floptical and Magneto Optical Disks
• Write-once CD-ROMS
• Jukeboxes, Stackloaders, and Similar Devices
• Hard disks

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Backing Up and restoring Files and Filesystems

• Tape archive (tar)
• Copy files to and from archive (cpio)
• Selective backup (dump)

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tar

• Format
• tar ltoptionsgt ltarchivegt ltfile(s)gt

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ltoptionsgt

• c Create an archive file and add files to it
• f ltarchivegt name of archive file
• r Record files at the end of the archive
  (append)
• t List the contents of an archive file
• u Update by adding new or changed files
• v Verbose mode
• x Extract files from archive (restore)
• z Compress files (gzip/gunzip)

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ltarchivegt

• Can be device, such as tape backup,
  recordable/rewritable CD ROM, or floppy
• Can be a path name on an existing mounted device
  (hard drive, floppy, etc)

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ltfile(s)gt

• Relative or absolute path name of files
• Must be specified for backup (tar responds with
  Cowardly refusing to create empty tape archive
  error message if you dont)
• A period indicates all files at the current
  location are to be backed up.
• Default for restore operation is all files in the
  archive.

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Backup Example

• tar cvf archive1.tar /lab8a/.
• Backs up all files in the /lab8a directory to an
  archive file called archive1.tar. Provides a
  complete list of backup operations.

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View Example

• tar tvf archive1.tar
• Prints a list of all files and directories in
  the archive.

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Restore Example

• tar xvf archive1.tar /lab8a
• Restores all files and directories in
  archive1.tar to the /lab8a directory

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Tips on using tar

• Case is important
• Spaces are important
• Using an incorrect option will cause
  unpredictable results
• Leaving out information will cause tar to hang
• ltCtrl Cgt will break you out of tar