[sonic_debian_extension] add docker script to SONiC filesystem (sonic…

…-net#5935)

- Why I did it
To allow SONiC Package Migration during SONiC-2-SONiC upgrade we need to start docker daemon in chroot-ed environment in new SONiC filesystem.
Later this script will be used to start dockerd in chroot environment on SONiC

- How I did it
Install a docker service script into /usr/lib/docker/ in SONiC filesystem.

- How to verify it
Install SONiC image on the switch, mount squashfs to some directory, mount overlay rw layer over squashfs, mount procfs and sysfs, mount docker library. Start the docker using:
root@sonic:~$ /usr/lib/docker/docker.sh start

Signed-off-by: Stepan Blyshchak <stepanb@nvidia.com>

files/build_templates/sonic_debian_extension.j2

@@ -31,10 +31,15 @@ BUILD_SCRIPTS_DIR=files/build_scripts
 BUILD_TEMPLATES=files/build_templates
 IMAGE_CONFIGS=files/image_config
 SCRIPTS_DIR=files/scripts
+DOCKER_SCRIPTS_DIR=files/docker
+
+DOCKER_CTL_DIR=/usr/lib/docker/
+DOCKER_CTL_SCRIPT="$DOCKER_CTL_DIR/docker.sh"
 
 # Define target fold macro
 FILESYSTEM_ROOT_USR="$FILESYSTEM_ROOT/usr"
-FILESYSTEM_ROOT_USR_LIB_SYSTEMD_SYSTEM="$FILESYSTEM_ROOT/usr/lib/systemd/system"
+FILESYSTEM_ROOT_USR_LIB="$FILESYSTEM_ROOT/usr/lib/"
+FILESYSTEM_ROOT_USR_LIB_SYSTEMD_SYSTEM="$FILESYSTEM_ROOT_USR_LIB/systemd/system"
 FILESYSTEM_ROOT_USR_SHARE="$FILESYSTEM_ROOT_USR/share"
 FILESYSTEM_ROOT_USR_SHARE_SONIC="$FILESYSTEM_ROOT_USR_SHARE/sonic"
 FILESYSTEM_ROOT_USR_SHARE_SONIC_SCRIPTS="$FILESYSTEM_ROOT_USR_SHARE_SONIC/scripts"
@@ -53,12 +58,14 @@ trap_push clean_sys
 sudo LANG=C chroot $FILESYSTEM_ROOT mount sysfs /sys -t sysfs
 
 sudo bash -c "echo \"DOCKER_OPTS=\"--storage-driver=overlay2\"\" >> $FILESYSTEM_ROOT/etc/default/docker"
-sudo cp files/docker/docker $FILESYSTEM_ROOT/etc/init.d/
+# Copy docker start script to be able to start docker in chroot
+sudo mkdir -p "$FILESYSTEM_ROOT/$DOCKER_CTL_DIR"
+sudo cp $DOCKER_SCRIPTS_DIR/docker "$FILESYSTEM_ROOT/$DOCKER_CTL_SCRIPT"
 if [[ $CONFIGURED_ARCH == armhf || $CONFIGURED_ARCH == arm64 ]]; then
     SONIC_NATIVE_DOCKERD_FOR_DOCKERFS=" -H unix:///dockerfs/var/run/docker.sock "
     SONIC_NATIVE_DOCKERD_FOR_DOCKERFS_PID="cat `pwd`/dockerfs/var/run/docker.pid"
 else
-    sudo chroot $FILESYSTEM_ROOT service docker start
+    sudo chroot $FILESYSTEM_ROOT $DOCKER_CTL_SCRIPT start
 fi
 
 # Apply apt configuration files
@@ -619,10 +626,9 @@ if [[ $CONFIGURED_ARCH == armhf || $CONFIGURED_ARCH == arm64 ]]; then
     sudo rm -fr $FILESYSTEM_ROOT/dockerfs
     sudo kill -9 `sudo $SONIC_NATIVE_DOCKERD_FOR_DOCKERFS_PID` || true
 else
-    sudo chroot $FILESYSTEM_ROOT service docker stop
+    sudo chroot $FILESYSTEM_ROOT $DOCKER_CTL_SCRIPT stop
 fi
 sudo umount /proc || true
-sudo rm $FILESYSTEM_ROOT/etc/init.d/docker
 
 sudo bash -c "echo { > $FILESYSTEM_ROOT_USR_SHARE_SONIC_TEMPLATES/ctr_image_names.json"
 {% for entry in feature_vs_image_names.split(' ') -%}