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deucalion backup

Backs up to your backup drive: everything (a full backup), or only the folders and files you choose (a partial backup). Only what is new or changed is copied; what is gone from your computer moves to Removed Files.

$ deucalion backup --help
usage: deucalion backup [-h] [--only PATH [PATH ...]] [--profile PROFILE] [--dry-run] [--details]
                        [--check-drive] [-y] [--no-system] [--no-admin] [--target NAME]

back up everything, or only some folders

options:
  -h, --help            show this help message and exit
  --only PATH [PATH ...]
                        back up only these folders/files
  --profile PROFILE     back up the folders saved in a profile
  --dry-run             show what would be copied, change nothing
  --details             list every file and warning
  --check-drive         also check that every file is really on the drive (slower)
  -y, --yes             don't ask for confirmation
  --no-system           don't save the system recipe
  --no-admin            don't ask for the administrator password (some system settings are then
                        not saved)
  --target NAME         which registered drive to use

Options

Option What it does
(none) A full backup: your home folder, your extra folders and the system recipe.
--only PATH … A partial backup of these folders or files only. They must be inside your home folder or an extra folder.
--profile NAME A partial backup of the folders saved in a profile. Can be combined with --only.
--dry-run Show what would be copied, with the largest folders, and copy nothing.
--details List every file that will be copied or moved to Removed Files, and every warning (normally the first 8 warnings are shown).
--check-drive Also check that every file in the backup is really on the drive, and copy again any that is missing. Slower: it lists every folder on the drive.
-y, --yes Don't ask when the drive holds another computer's or user's backup (see below).
--no-system Don't save the system recipe (full backups only).
--no-admin Don't ask for the administrator password: the protected settings (Wi-Fi/VPN connections, root-only /etc files) are not updated.
--target NAME Which backup drive to use.

What it prints

First the drive, then (full backups) the system recipe being saved, then the plan, then the result:

$ deucalion backup
Backing up to Alex Backup  /media/alex/Alex Backup/Deucalion-Backup
Saving the system recipe (packages, settings, services) — you may be asked for your administrator password…
Backup plan (full: everything)
  New files:               3   2.4 MB
  Changed files:           2   86 B (previous versions go to _removed/)
  Gone/excluded:           1   38 B (moved to _removed/)
  Unchanged:           1,043   488.1 MB
Backup finished in 0s: copied 5 files (2.4 MB), moved 1 item to _removed/.
Log: /media/alex/Alex Backup/Deucalion-Backup/.deucalion/logs/2026-10-12_091015-backup.log
Line Meaning
New files Not in the backup yet; will be copied.
Changed files Changed since the last backup; will be copied, and the previous versions go to Removed Files.
Gone/excluded In the backup, but no longer on your computer (or now left out); moved to Removed Files.
Unchanged Already backed up as they are.

While copying, one line shows a progress bar, how much is copied, the speed, the time left and the current file. At the end it says how many files were copied and how many items moved to Removed Files, and where the log is. After a backup, the copy of Deucalion and the READ-ME file on the drive's normal part are refreshed.

A dry run

--dry-run stops after the plan and also lists the largest folders, so you can see what takes space:

$ deucalion backup --dry-run
Backing up to Alex Backup  /media/alex/Alex Backup/Deucalion-Backup
Saving the system recipe (packages, settings, services)…
Backup plan (full: everything)
  New files:               3   2.4 MB
  Changed files:           2   86 B (previous versions go to _removed/)
  Gone/excluded:           1   38 B (moved to _removed/)
  Unchanged:           1,043   488.1 MB
  Largest folders in this backup:
      333.8 MB           2 files  home/Videos
       86.0 MB          34 files  home/Pictures
       63.4 MB           3 files  home/Music
        5.8 MB         371 files  home/Deucalion
      875.1 KB          63 files  home/.local
      432.8 KB          11 files  home/Documents
      128.8 KB         467 files  home/Projects
       81.3 KB          61 files  system/etc
       49.0 KB          13 files  system/packages
        4.8 KB           6 files  home (files)
        2.0 KB           3 files  system/services
        1.9 KB           2 files  system (files)
  Warnings (1):
    System settings (/etc, network) were not updated because administrator access was not used; the copy from an earlier backup is kept.
Dry run: nothing was copied. Add --details to list every file.

Dry runs don't ask for your password

So they can't read the protected settings. The warning "System settings (/etc, network) were not updated because administrator access was not used; the copy from an earlier backup is kept." only means that; the real backup will ask for the password.

A partial backup

$ deucalion backup --only ~/Documents ~/Pictures
Backing up to Alex Backup  /media/alex/Alex Backup/Deucalion-Backup
Backup plan (partial: /home/alex/Documents, /home/alex/Pictures)
  New files:               0   0 B
  Changed files:           1   72 B (previous versions go to _removed/)
  Gone/excluded:           0   0 B (moved to _removed/)
  Unchanged:              44   86.4 MB
Backup finished in 0s: copied 1 file (72 B), moved 0 items to _removed/.
Log: /media/alex/Alex Backup/Deucalion-Backup/.deucalion/logs/2026-10-12_091020-backup.log

Checks before copying

Deucalion checks, and stops without copying anything, when:

  • the drive is too small: "Not enough space on the drive: this backup needs about … but only … is free. You can free space by emptying _removed/ (deucalion removed empty) or excluding large folders." (exit code 1). See Free space on the drive.
  • the drive holds another computer's or user's backup: it prints "This drive holds the backup of alex@alex-laptop (home folder /home/alex), but this is …" and asks Continue anyway? Backing up would make the drive mirror this computer and move everything that is only in the old backup to Removed Files. On a new computer, rebuild or restore first. --yes answers yes.

It also warns (without stopping) when the drive is not encrypted and your backup includes keys or logged-in sessions (.ssh, .gnupg, password stores, keyrings, browser profiles).

Stopping and interruptions

Press Ctrl+C once to stop safely: "Stopped. N files were copied; the next backup continues from here." (exit code 130). A backup that was killed, or whose drive was unplugged or ran full, is also completed by the next backup, with no duplicates.

Results

End Exit code
Backup finished in …: copied N files (…), moved N items to _removed/. 0
The same, followed by "Some warnings above.": some files couldn't be read or were skipped; see the log. 0
Everything is already up to date. then Backup finished in 0s: copied 0 files … (nothing to copy) 0
Backup failed: … (for example the drive filled up while copying) 1
Stopped. … 130