hooks_docker-btrfs

#!/usr/bin/bash

run_hook() {
    docker_rwlayer=$(echo $rootflags | grep -o "subvol=[^,]*" | grep -o "[^=]*\$")

    mkdir -p /docker_root
    mkdir -p /var/lib/docker
    mkdir -p /top_layer

    msg ":: mounting "$root" at /docker_root"
    rootdev=$(resolve_device "$root") && root=$rootdev
    unset rootdev
    if ! mount -t btrfs "$root" "/docker_root"; then
        echo "You are now being dropped into an emergency shell."
        launch_interactive_shell
        msg "Trying to continue (this will most likely fail) ..."
    fi

    msg ":: bind mounting "/docker_root/$docker_path" at /var/lib/docker"
    if ! mount -o bind "/docker_root/$docker_path" "/var/lib/docker"; then
        echo "You are now being dropped into an emergency shell."
        launch_interactive_shell
        msg "Trying to continue (this will most likely fail) ..."
    fi

    msg ":: getting docker cache subvolume"
    cache_id=$(get-docker-cache-id)

    msg ":: creating rwlayer"
    [ -d /docker_root/"$docker_rwlayer" ] && btrfs subvolume delete /docker_root/"$docker_rwlayer"
    if ! btrfs subvolume snapshot /var/lib/docker/btrfs/subvolumes/$cache_id /docker_root/"$docker_rwlayer"; then
        echo "You are now being dropped into an emergency shell."
        launch_interactive_shell
        msg "Trying to continue (this will most likely fail) ..."
    fi

    msg ":: mounting top layer drive"
    toplayerdev=$(resolve_device "$toplayer") && root=$toplayerdev
    unset toplayerdev
    if ! mount ${toplayerfstype:+-t $toplayerfstype} ${toplayerflags:+-o $toplayerflags} "$toplayer" "/top_layer"; then
        echo "You are now being dropped into an emergency shell."
        launch_interactive_shell
        msg "Trying to continue (this will most likely fail) ..."
    fi

    msg ":: applying top layer"
    cp -a /top_layer/"$toplayer_path"/* /docker_root/"$docker_rwlayer"/

    # cleaning
    cd /
    umount /top_layer
    umount /var/lib/docker
    umount /docker_root
}

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