RSync

Abdun Nihaal
https://nihaal.me
12 June 2021 at ILUGC

You need a backup

• 3-2-1 Backup Strategy
  • Your working copy
  • Local backup (for quick access)
  • Remote backup (if we lose both local copy)
• Set a system in place

RSync

• Written in C
• Supports Windows, Linux, OS X, BSD
• Multiple GUI Frontends available (GSync, QSync, Zynk, etc)

• General format

  rsync options /path/to/source/folder /path/to/backup/folder
  

What's good?

• Uses a diff based transfer algorithm to reduce bandwidth usage
• Works over SSH to backup remote files
• Good for unidirectional static backups

What's not good?

• Cannot be used easily for bi directional transfers
  • If you modify both copies simultaneously, try Syncthing instead
• Moved and renamed files will be treated like new files and will be copied again. Some workarounds:
  • -y –fuzzy option, detects renames within a directory
  • Using hard links
• Diff based algorithm does not work well for compressed files

Things to note

• RSync has different behaviour with and without trailing backslash
• Databases need to be dumped to files for RSync to backup
• Can be automated using crontab or SystemD timers
• Always do a dry run before executing (especially with –delete)

Options

More options

Common uses

• Full system backup (For more info)

  sudo rsync -aAXv \
  --exclude={"/dev/*","/proc/*","/sys/*","/tmp/*",\
             "/run/*","/mnt/*","/media/*","/lost+found"} \
  / /path/to/backup/folder
  

• Backup remote folder using ssh

  rsync -ave ssh /path/to/source/folder user@remote:~/backup/folder
  

• Incremental backup

  rsync -arvhP --delete /path/to/source/folder /path/to/backup/folder