Add option for dynamic snapshot_name (in conjunction with wildcards)

[digint]

Wildcards are not very useful if the subvolume names are identical.

E.g. lxc containers are created as <container_name>/rootfs, which results in all btrbk snapshots named rootfs when configuring subvolume */rootfs.

See #71 (this comment)

[digint]

See discussion: #230 Subvolume wildcards are not recursive

[ceremcem]

This goal can also be accomplished by dynamically generating the static BTRBK configuration file. Here is the proof of concept script that I'm currently using, gen-config.sh:

#!/bin/bash
set -eu

config=${1:-}

[[ -f $config ]] || { \
    cat << EOL

Description:

Generates BTRBK config file by adding subvolumes into the 
configuration under \$subvolume.

Required \$snapshot_dir's are created automatically.

Usage:

    $(basename $0) path/to/orig.config > generated.config

Then use the generated.config as usual.

EOL
    exit 1;
}

errcho(){ >&2 echo -e "$@"; }

btrfs_ls(){
    sudo ./btrbk ls "$1" | tail -n+2 | awk '{print $4}' | sort -r
}

# Print the original config
cat $config
echo

# Print generated config
while read key value; do
    case $key in
        snapshot_dir|volume|subvolume|target)
            declare $key=$value
            ;;
    esac
done < $config

# TODO: assign them to an array
src="$volume/$subvolume"
dest="$volume/$snapshot_dir"
target=$target

exclude_list=("tmp")

btrfs_ls "$src" | while read sub; do
    [[ "$(basename $sub)" == "tmp" ]] && {  errcho "Skipping $sub..."; continue; }
    rel=$(readlink -m "${sub#${src%/}}")
    new_snapshot_dir=$(readlink -m $dest/$(dirname $rel))
    #echo will backup $sub like $new_snapshot_dir/$(basename $sub).1234567890;
    _subvolume="${sub#$volume/}"
    _snapshot_dir="${new_snapshot_dir#$volume/}"
    _target="$target/$(dirname $rel)"
    if [[ ! -d "$new_snapshot_dir" ]]; then
        errcho "Creating $new_snapshot_dir"
        sudo mkdir -p "$new_snapshot_dir"
    fi
    if [[ -d "$target" && ! -d "$_target" ]]; then
        errcho "Creating $_target"
        sudo mkdir -p "$_target"
    fi
    # Generate actual BTRBK configuration
    echo "volume    $volume"
    echo "  subvolume       $_subvolume"
    echo "  snapshot_dir    $_snapshot_dir"
    echo "  target          $_target"
    echo
done

Changelog

1. Fixed "do not generate snapshot_dir's if they exist" logic.

This script generates a configuration from:

timestamp_format        long

snapshot_preserve_min   2d
snapshot_preserve      14d

target_preserve_min    5h
target_preserve        20d 10w *m

snapshot_dir           snapshots/erik3

volume /mnt/heybe-root
  target /mnt/masa-root/snapshots/erik3
  subvolume rootfs

...the following one:

timestamp_format        long

snapshot_preserve_min   2d
snapshot_preserve      14d

target_preserve_min    5h
target_preserve        20d 10w *m

snapshot_dir           snapshots/erik3

volume /mnt/heybe-root
  target /mnt/masa-root/snapshots/erik3
  subvolume rootfs


volume /mnt/heybe-root
  subvolume rootfs/var/lib/lxc/fc4/rootfs
  snapshot_dir snapshots/erik3/var/lib/lxc/fc4
  target /mnt/masa-root/snapshots/erik3//var/lib/lxc/fc4

volume /mnt/heybe-root
  subvolume rootfs/var/lib/lxc/couchdb-test/rootfs
  snapshot_dir snapshots/erik3/var/lib/lxc/couchdb-test
  target /mnt/masa-root/snapshots/erik3//var/lib/lxc/couchdb-test

volume /mnt/heybe-root
  subvolume rootfs/var/lib/lxc/couchdb-erik/rootfs
  snapshot_dir snapshots/erik3/var/lib/lxc/couchdb-erik
  target /mnt/masa-root/snapshots/erik3//var/lib/lxc/couchdb-erik

volume /mnt/heybe-root
  subvolume rootfs/var/cache/lxc/debian/rootfs-stretch-amd64
  snapshot_dir snapshots/erik3/var/cache/lxc/debian
  target /mnt/masa-root/snapshots/erik3//var/cache/lxc/debian

volume /mnt/heybe-root
  subvolume rootfs/var/cache/lxc/debian/rootfs-buster-amd64
  snapshot_dir snapshots/erik3/var/cache/lxc/debian
  target /mnt/masa-root/snapshots/erik3//var/cache/lxc/debian

volume /mnt/heybe-root
  subvolume rootfs/home/ceremcem/foo/bar
  snapshot_dir snapshots/erik3/home/ceremcem/foo
  target /mnt/masa-root/snapshots/erik3//home/ceremcem/foo