fstab generator

fstab.gen.py

#!/usr/bin/python3
import yaml
import sys
from pathlib import Path

HIDE_OPTIONS = ['x-gvfs-hide']

def generate_fstab(yaml_file: Path):
    with yaml_file.open('r') as file:
        config = yaml.safe_load(file)

    fstab_entries = []

    for entry in config:
        group = []
        fs = entry['fs']
        fstype = entry['type']
        hide = entry.get('hide', False)
        dump = entry.get('dump', 0)
        passno = entry.get('pass', 0)
        mount = entry.get('mount', 'none')
        options: list = entry.get('options', ['defaults'])
        subvol = entry.get('subvol')

        if mount == 'none' and fstype not in ['swap']:
            raise ValueError(f'mount point for {fs} not specified')

        # [mount] can be a list of btrfs subvolumes, a list of strings, or just a string

        if isinstance(mount, list):
            for mount in entry['mount']:
                if isinstance(mount, str):
                    path = mount
                    path_subvol = subvol
                    path_options = options.copy()
                    path_hide = hide
                else:
                    path = mount['path']
                    path_subvol = mount.get('subvol', subvol)
                    path_options: list[str] = mount.get('options', [])
                    if not mount.get('override', False):
                        path_options.extend(options)
                    path_hide = mount.get('hide', hide)
                
                if fstype == "btrfs":
                    path_options.append(f'subvol={path_subvol}')

                if path_hide:
                    path_options.extend(HIDE_OPTIONS)

                group.append(f"{fs} {path} {fstype} {','.join(path_options)} {dump} {passno}")
        else:
            if hide:
                options.extend(HIDE_OPTIONS)
            if fstype == "btrfs":
                options.append(f'subvol={subvol}')
            group.append(f"{fs} {mount} {fstype} {','.join(options)} {dump} {passno}")
        fstab_entries.append(group)

    return '\n\n'.join('\n'.join(group) for group in fstab_entries)

if __name__ == "__main__":
    yaml_file = Path(sys.argv[1] if len(sys.argv) > 1 else '/etc/fstab.yml')
    if not yaml_file.exists():
        print(f"{yaml_file} does not exist")
        raise SystemExit
    fstab_content = generate_fstab(yaml_file)
    print(fstab_content)

sample fstab.yml

- fs: UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
  type: btrfs
  options:
    - rw
    - noatime
    - user_subvol_rm_allowed
    - compress=zstd:1
    - discard=async
  hide: false
  mount:
    - path: /
      subvol: /arch
    - path: /home/user
      subvol: /home/1000

- fs: UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
  type: btrfs
  options: 
    - rw
    - noatime
    - user_subvol_rm_allowed
    - compress=zstd:2
    - discard=async
  mount:
    - /media/secondary
    - path: /home/user/src/chromium
      subvol: /chromium
    - path: /home/user/src/aosp
      subvol: /aosp
    - path: /home/user/steam
      subvol: /steam
      hide: true
    - path: /recovery
      subvol: /arch
      hide: true

- &esp
  fs: UUID=FFFF-FFFF
  type: vfat
  pass: 2
  options: 
    - rw
    - noatime
    - fmask=0177
    - dmask=0077
    - codepage=437
    - iocharset=ascii
    - shortname=mixed
    - utf8
    - errors=remount-ro
  hide: true
  mount:
    - /efi
    - /recovery/efi


- &swap
  fs: UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
  type: swap
  options: 
    - defaults
    - pri=10
  hide: false

- <<: *swap
  fs: UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx