Use Deucalion without a desktop¶

What you'll do: back up, restore or rebuild a computer you reach over SSH, or a server without a desktop.
What you need: a terminal on that computer; sudo rights there.
How long it takes: as on a desktop.

Everything works from the command line. A few things behave differently when there is no desktop session.

What is different¶

The app doesn't open. Plain deucalion prints the list of commands:

$ bin/deucalion
usage: deucalion [-h] [--version] COMMAND ...

Back up your Ubuntu machine to an external drive, and restore or rebuild from it.

positional arguments:
  COMMAND
    gui          open the app (also what plain 'deucalion' does)
    deps         check (and install) what Deucalion needs, including VeraCrypt
    drives       list connected drives
    register     use a drive (or a folder on it) for backups
    targets      list registered backup drives
    setup-drive  prepare a drive for backups (format, encrypt)
    open         unlock an encrypted backup drive
    close        lock/unmount the backup drive so it can be unplugged
    backup       back up everything, or only some folders
    status       show the state of the backup
    ls           list what is in the backup (with original names)
    restore      restore files or folders from the backup
    rebuild      rebuild this machine from a backup (new machine or new Ubuntu)
    verify       check the backup on the drive is complete and undamaged
    removed      list or empty _removed/ (old versions and deleted files)
    exclude      manage what is left out of your home backup
    folder       manage extra folders outside your home (e.g. /srv)
    profile      manage saved selections for partial backups
    config       show or edit the configuration

options:
  -h, --help     show this help message and exit
  --version      show program's version number and exit

Administrator access goes through sudo. Without a desktop, Deucalion uses sudo for the administrator helper:

if sudo works without a password for you (sudo -n true succeeds, as on many cloud machines), Deucalion uses it and asks nothing;
otherwise it asks for your password in the terminal: [Deucalion] administrator password for …:.

Mounting drives needs administrator rights. On a desktop, Ubuntu's disk service (UDisks) lets the person at the computer mount and unlock external drives. Over SSH it asks for an administrator password instead: udisksctl mount asks for it in the terminal, and without a way to ask it refuses:

$ udisksctl mount --no-user-interaction -b /dev/sda1
Error mounting /dev/sda1: GDBus.Error:org.freedesktop.UDisks2.Error.NotAuthorizedCanObtain: Not authorized to perform operation

Deucalion's own disk-service calls can't ask either, so over SSH they fail with "Not authorized to perform operation".

So mount the drive (or its normal part) yourself with sudo, owned by you:

$ sudo mkdir -p /mnt/backup-drive && sudo mount -o uid=$(id -u),gid=$(id -g) /dev/sda1 /mnt/backup-drive && ls /mnt/backup-drive
Deucalion-Tool  READ-ME-FIRST.txt

Then Deucalion finds the backup as usual. A VeraCrypt backup is unlocked through the administrator helper, so it works the same as on a desktop:

$ bin/deucalion open
Backup password:
  Unlocking (you will be asked for your administrator password)…
  Unlocking (VeraCrypt volumes can take up to a minute)…
Registered backup drive 'Alex Backup' on this machine.
Backup drive 'Alex Backup' is open: /media/alexk/Alex Backup/Deucalion-Backup

This affects LUKS drives and LUKS encrypted folders, and setting up drives (setup-drive): Deucalion does these through the disk service, so over SSH they fail with "Not authorized to perform operation". Set up drives on a desktop, or unlock LUKS by hand (sudo cryptsetup open /dev/sdX2 backup then sudo mount -o uid=$(id -u) /dev/mapper/backup /mnt/x) and register the folder.

A rebuild restores ~/.ssh. Your home folder's .ssh folder comes back from the backup, including authorized_keys, which lists the keys allowed to log in over SSH. If you reach the new computer over SSH with a key that isn't in the old computer's authorized_keys, you will be locked out after step 4. Before the rebuild, add your key to the old computer's ~/.ssh/authorized_keys and back up, or untick .ssh/ in step 4.

No desktop settings. On a server without GNOME, the desktop settings step of a rebuild says there is nothing to do; desktop settings are not saved when dconf isn't installed.

VeraCrypt may need libsm6. VeraCrypt's official package needs the libsm6 library without declaring it; every desktop has it, a minimal server may not. Install it with sudo apt install libsm6 if VeraCrypt fails with "libSM.so.6: cannot open shared object file".

Questions need a terminal. Commands that ask something need a terminal (an interactive SSH session). In scripts, answer in advance: --yes for questions, --yes-erase sdX to erase a drive; rebuild needs --yes (apply the pre-selected items) or --dry-run. Passwords can be given on standard input with DEUCALION_PASSWORD_STDIN=1 (one line per password asked):

printf '%s\n' "$BACKUP_PASSWORD" | DEUCALION_PASSWORD_STDIN=1 deucalion open

Warning

Anything that stores the password in a file or in your shell history is a risk. Prefer typing it in an interactive session.

A rebuild over SSH¶

Mount the drive's normal part with sudo (above), and cd into its Deucalion-Tool folder.
bin/deucalion open (password; administrator password if sudo asks).
bin/deucalion rebuild, answering each step (see rebuild).
Log out and back in.

What you have now: Deucalion working on a computer without a desktop.