lxc-clone: support 'permanent ephemeral' containers

All of this needs a rewrite/redesign, and that will be coming (details below), but for now You can start 'non-ephemeral ephemeral' containers using lxc-start-ephemeral -o oldname -n newname --keep-data When you shut that down, the container stick around and can be restarted. Now lxc-clone will recognize such a container by the presence of the delta0/ which contains the read-write overlayfs layer. This means you can do incremental development of containers, i.e. lxc-create -t ubuntu -n r1 lxc-start-ephemeral --keep-data -o r1 -n r1-2 # make some changes, poweroff lxc-clone -o r1-2 -n r1-3 # make some changes... lxc-clone -o r1-3 -n r1-4 # etc... Now, as for design changes... from a higher level 1. lxc-clone should be re-written in c and exported through the api. 2. lxc-clone should support overlayfs and aufs 3. lxc-start-ephemeral should become a thin layer which clones a container, starts and stops and destroys it. at a lower level, 1. the api should support container->setup_mounts 2. lxc-clone should be written as a set of backend classes which can copy mounts to each other. So when you load a container which is lvm-backed, it creates a lvm backend class. That class instance can be converted into a loopback or qemu-nbd or directory backed class. A directory-backed class can be converted into a overlayfs or aufs backed class, which (a) uses the dirctory-backed class as the read-only base, and (b) pins the base container (so it can't be deleted until all snapshots are deleted). Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com> Acked-by: Stéphane Graber <stgraber@ubuntu.com>

lxc-clone: support 'permanent ephemeral' containers
48853811 · Serge Hallyn · Stéphane Graber · f63b1efd · 48853811
Commit 48853811 authored Mar 27, 2013 by Serge Hallyn Committed by Stéphane Graber Mar 27, 2013
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lxc-clone.in src/lxc/lxc-clone.in +17 -0

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--- a/src/lxc/lxc-clone.in
+++ b/src/lxc/lxc-clone.in
@@ -251,6 +251,23 @@ elif which btrfs >/dev/null 2>&1 && btrfs subvolume list $oldroot >/dev/null 2>&
    # if oldroot is a btrfs subvolume, assume they want a snapshot
    btrfs subvolume snapshot "$oldroot" "$rootfs" 2>&1 || { echo "$(basename $0): btrfs snapshot failed" >&2; false; }
    echo "lxc.rootfs = $rootfs" >> "$lxc_path/$lxc_new/config"
+elif [ -d $lxc_path/$lxc_orig/delta0 ]; then # this is a quasi-ephemeral container
+    if [ $container_running = "True" ]; then
+        echo "$(basename $0): container $lxc_orig is running." >&2
+        cleanup
+    fi
+    rsync -Hax $lxc_path/$lxc_orig/delta0 $lxc_path/$lxc_new/
+    touch $lxc_path/$lxc_new/configured
+    cp -f $lxc_path/$lxc_orig/pre-mount $lxc_path/$lxc_new/
+    sed -i "s@$lxc_path/$lxc_orig@$lxc_path/$lxc_new@g" $lxc_path/$lxc_new/config
+    sed -i "s@$lxc_path/$lxc_orig@$lxc_path/$lxc_new@g" $lxc_path/$lxc_new/pre-mount
+    sed -i "s@LXC_NAME=\"$lxc_orig@LXC_NAME=\"$lxc_new@" $lxc_path/$lxc_new/pre-mount
+    # lxc-start-ephemeral will have updated /etc/hostname and such under the
+    # delta0, so just mounting the delta should suffice.
+    mkdir -p $rootfs
+    mount --bind $lxc_path/$lxc_new/delta0 $rootfs
+    mounted=1
+    echo "lxc.rootfs = $rootfs" >> "$lxc_path/$lxc_new/config"
 else
    if [ $snapshot = "yes" ]; then
        echo "$(basename $0): cannot snapshot a directory" >&2