Backup Notes

Utilities

Tar

Tar is great for creating archives of multiple directories or files into a single file. It also supports compression and can be combined with other tools for encryption and integrity checks.

Usage

Compressing directories into a .txz archive:

tar -cJf file.txz /path/to/directorie/1 /path/to/directorie/2
  • Use "-J" to use the xz protocol.
  • Use "-cf" to create a new file.

Using multithreading compression:

tar -cf - /path/to/directorie/1 /path/to/directorie/2 | xz -z -T0 -9 > file.txz
  • "-T0" uses all available CPU cores.
  • "-9" is the maximum compression level.

Extracting an archive:

tar -xJf file.txz

GPG

GPG can be used to encrypt files for secure storage or transfer.

Usage

Create a keypair:

gpg --full-generate-key

Get key information:

gpg --list-keys

For the key ID, use the long format (16 characters).

gpg --list-keys --keyid-format LONG

Export public key:

gpg --export --armor <recipient_key_id> > publickey.asc

Import public key:

gpg --import publickey.asc

Export secret key for backup:

gpg -o private-backup.gpg --export-options backup --export-secret-keys <email_or_key_id>

Import the backup key:

gpg --import-options restore --import private-backup.gpg

gpg --edit-key username@example.com

> trust
> 5 (ultimately)
> save

Encrypt a file with a recipient

gpg --encrypt --recipient <recipient_key_id> file

Decrypt a file

gpg --decrypt file.gpg > file

Encrypt a file with password

gpg --encrypt --symmetric file

Rsync

Rsync is a powerful tool for synchronizing files and directories between two locations, either locally or over a network.

Usage

rsync -arzuvhP /path/to/source /path/to/destiny
  • "a" for archive mode
  • "r" for recursive
  • "z" for compression on transit (useful in network)
  • "u" for skipping files newer on receiver
  • "v" for verbose
  • "h" for human readable

  • "P" for progress

  • "c" for checksum

  • "i" for showing changes in a verbose mode

  • "--ignore-existing" for leaving untouched the files on destination

  • "-delete" for deleting files on destination

"-n" for dry run

When using -i (--itemize-changes) the output of the changes will be more verbose of why the changes are being done, running it with --dry-run is a secure practice in case you want to use -delete, the output description is:

YXcstpoguax  path/to/file
|||||||||||
`----------- the type of update being done::
 ||||||||||   <: file is being transferred to the remote host (sent).
 ||||||||||   >: file is being transferred to the local host (received).
 ||||||||||   c: local change/creation for the item, such as:
 ||||||||||      - the creation of a directory
 ||||||||||      - the changing of a symlink,
 ||||||||||      - etc.
 ||||||||||   h: the item is a hard link to another item (requires --hard-links).
 ||||||||||   .: the item is not being updated (though it might have attributes that are being modified).
 ||||||||||   *: means that the rest of the itemized-output area contains a message (e.g. "deleting").
 ||||||||||
 `---------- the file type:
  |||||||||   f for a file,
  |||||||||   d for a directory,
  |||||||||   L for a symlink,
  |||||||||   D for a device,
  |||||||||   S for a special file (e.g. named sockets and fifos).
  |||||||||
  `--------- c: different checksum (for regular files)
   ||||||||     changed value (for symlink, device, and special file)
   `-------- s: Size is different
    `------- t: Modification time is different
     `------ p: Permission are different
      `----- o: Owner is different
       `---- g: Group is different
        `--- u: The u slot is reserved for future use.
         `-- a: The ACL information changed

Btrfs

Btrfs is a modern filesystem that supports advanced features like snapshots, subvolumes, and built-in RAID support. It is well-suited for backup solutions due to its snapshot capabilities and efficient storage management.

Usage

Format a partition with Btrfs:

sudo mkfs.btrfs /dev/sdXn

To mount a Btrfs filesystem:

sudo mount -o options -t btrfs /dev/sdXn /mnt/point

Options can include:

  • "compress=zstd" for compression (also supported: lzo, zlis)
  • "noatime" to disable access time updates
  • "subvol=subvolume_name" to mount a specific subvolume
  • "space_cache=v2" for improved space cache management
  • "autodefrag" to enable automatic defragmentation

Taking a snapshot:

sudo btrfs subvolume snapshot -r /mnt/point/subvolume /mnt/point/snapshot_name

Sending a snapshot to another location:

sudo btrfs send /mnt/point/snapshot_name | sudo btrfs receive /mnt/dest/point

Sending an incremental snapshot:

sudo btrfs send -p /mnt/point/snapshot_previous /mnt/point/snapshot_new | sudo btrfs receive /mnt/dest/point

Delete a snapshot:

sudo btrfs subvolume delete /mnt/point/snapshot_name