initial version

5 files changed, 142 insertions, 0 deletions

diff --git a/.SRCINFO b/.SRCINFO
new file mode 100644
index 000000000000..cdc75a36056b
--- /dev/null
+++ b/.SRCINFO
@@ -0,0 +1,20 @@
+pkgbase = mkinitcpio-docker-hooks
+	pkgdesc = mkinitcpio hooks that provides support for using docker image as root
+	pkgver = 1.0
+	pkgrel = 1
+	url = https://github.com/zasdfgbnm/mkinitcpio-docker-hooks
+	arch = any
+	groups = base
+	license = GPL
+	depends = mkinitcpio
+	depends = jq
+	backup = etc/docker-btrfs.sh
+	source = install_docker-btrfs
+	source = hooks_docker-btrfs
+	source = etc_docker-btrfs.sh
+	md5sums = 0da33ef9ff132737a09173fdd45cddd6
+	md5sums = e1d51dd467412b48361c648226e6b57e
+	md5sums = a1243d4a874f69ef696f5c6ac58424cb
+
+pkgname = mkinitcpio-docker-hooks
+
diff --git a/PKGBUILD b/PKGBUILD
new file mode 100644
index 000000000000..c400a964914a
--- /dev/null
+++ b/PKGBUILD
@@ -0,0 +1,21 @@
+# Maintainer: Xiang Gao <qasdfgtyuiop at gmail dot com>
+pkgname=mkinitcpio-docker-hooks
+pkgver=1.0
+pkgrel=1
+pkgdesc="mkinitcpio hooks that provides support for using docker image as root"
+arch=(any)
+url="https://github.com/zasdfgbnm/mkinitcpio-docker-hooks"
+license=('GPL')
+groups=('base')
+depends=('mkinitcpio' 'jq')
+backup=(etc/docker-btrfs.sh)
+source=('install_docker-btrfs' 'hooks_docker-btrfs' 'etc_docker-btrfs.sh')
+md5sums=('0da33ef9ff132737a09173fdd45cddd6'
+         'e1d51dd467412b48361c648226e6b57e'
+         'a1243d4a874f69ef696f5c6ac58424cb')
+
+package() {
+    install -Dm644 install_docker-btrfs "${pkgdir}/usr/lib/initcpio/install/docker-btrfs"
+    install -Dm644 hooks_docker-btrfs "${pkgdir}/usr/lib/initcpio/hooks/docker-btrfs"
+    install -Dm644 etc_docker-btrfs.sh "${pkgdir}/etc/docker-btrfs.sh"
+}
diff --git a/etc_docker-btrfs.sh b/etc_docker-btrfs.sh
new file mode 100644
index 000000000000..1843e6c864aa
--- /dev/null
+++ b/etc_docker-btrfs.sh
@@ -0,0 +1,2 @@
+docker_image=archlinux/base
+docker_tag=latest
diff --git a/hooks_docker-btrfs b/hooks_docker-btrfs
new file mode 100755
index 000000000000..31efedf9ebc9
--- /dev/null
+++ b/hooks_docker-btrfs
@@ -0,0 +1,61 @@
+#!/usr/bin/bash
+
+run_hook() {
+    . /etc/docker-btrfs.sh
+    docker_rwlayer=$(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"
+    cd /var/lib/docker/image/btrfs
+    image_id=$(jq ".Repositories.\"$docker_image\".\"$docker_image:$docker_tag\"" repositories.json | sed 's/:/\//g;s/"//g')
+    last_layer_id=$(jq '.rootfs.diff_ids[]' imagedb/content/$image_id | sed 's/"//g' | tail -n 1)
+    cache_id_file=$(grep $last_layer_id -rl layerdb | sed 's/diff/cache-id/g')
+    cache_id=$(cat $cache_id_file)
+
+    msg ":: creating rwlayer"
+    [ -d /docker_root/"$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 -r /top_layer/"$toplayer_path"/* /docker_root/"$docker_rwlayer"/
+
+    # cleaning
+    cd /
+    umount /top_layer
+    umount /var/lib/docker
+    umount /docker_root
+}
+
+# vim: set ft=sh ts=4 sw=4 et:
\ No newline at end of file
diff --git a/install_docker-btrfs b/install_docker-btrfs
new file mode 100755
index 000000000000..272329d55451
--- /dev/null
+++ b/install_docker-btrfs
@@ -0,0 +1,38 @@
+#!/bin/bash
+
+build() {
+    add_module btrfs
+    add_binary btrfs
+    add_binary btrfsck
+    add_binary jq
+    add_file /etc/docker-btrfs.sh
+    add_runscript
+}
+
+help() {
+    cat <<HELPEOF
+This hook provides support for using docker image as root. Only btrfs
+is supported. This hook creates an rwlayer as a snapshot of the subvolume
+in docker cache of the specified image and use this rwlayer as root.
+The rwlayer is not automatically saved and will be emptied the next time
+during boot.
+
+To setup this hook:
+
+In /etc/docker-btrfs.sh, the user specify the image and tag that would
+be used as root. During installation, this file will be copied to the
+initramfs generated and read by the runtime hook during booting.
+
+While booting, the kernel option "root" should be the drive that contains
+the docker directory (the directory that will become /var/lib/docker after
+boot). The "docker_path" is used to specify the relative path of docker
+directory with respect to "root". The "rootflags" should at least have a
+"subvol=******"; this subvolume will become the rwlayer, and all existing
+data will be emptied. The "toplayer" is the drive that stores top layer
+data which will be applied to rwlayer after rwlayer is mounted. The
+"toplayerfstype", "toplayerflags" playes the same role to top layer as
+"rootfstype", "rootflags" plays to root. The "toplayer_path" is the relative
+path of the directory of the top layer with respect to "toplayer".
+
+HELPEOF
+}
\ No newline at end of file