[Lxc-users] lxc-clone

Tue Apr 5 11:29:31 UTC 2011

On 03/30/2011 06:29 PM, Serge E. Hallyn wrote:
> I've replaced most of my previous use of kvm and cloud instances for bug
> investigations with lxc instances.  To emulate my older workflows, I've
> created lxc-clone.  My diff against the current natty lxc package is
> attached.  I've written up how I use this at s3hh.wordpress.com.  Briefly,
> I have a single pristine container, with LVM rootfs, for each of lucid,
> maverick, and natty.  When I want a container, I
>
> 	lxc-clone -o natty -n n1 -s
> 	lxc-start -n n1
>
> which takes about 5 seconds altogether.  Ruin n1 however I like, and
>
> 	lxc-destroy -l -n n1
>
> when done.
>
> It needs fleshing out, but it's at the point where it does exactly what
> I need.  The next thing I'm likely to add will be btrfs snapshotting,
> not sure when.
>
> Daniel, is this something you'd consider adding?  I assume that if so,
> then there are changes you'd like to make to the interface :)

Hi Serge,

yes, it is an interesting feature, thanks for the patch.

I think more configuration tweaking will be needed but this patch looks 
good for me.

> === modified file 'configure.ac'
> --- configure.ac	2011-03-10 07:25:34 +0000
> +++ configure.ac	2011-03-30 15:36:58 +0000
> @@ -156,6 +156,7 @@
>   	src/lxc/lxc-setuid
>   	src/lxc/lxc-version
>   	src/lxc/lxc-create
> +	src/lxc/lxc-clone
>   	src/lxc/lxc-destroy
>
>   ])
>
> === modified file 'lxc.spec'

It should be lxc.spec.in

> --- lxc.spec	2011-03-10 07:25:34 +0000
> +++ lxc.spec	2011-03-30 15:36:58 +0000
> @@ -78,6 +78,7 @@
>   %{_bindir}/*
>   %attr(4111,root,root) %{_bindir}/lxc-attach
>   %attr(4111,root,root) %{_bindir}/lxc-create
> +%attr(4111,root,root) %{_bindir}/lxc-clone
>   %attr(4111,root,root) %{_bindir}/lxc-start
>   %attr(4111,root,root) %{_bindir}/lxc-netstat
>   %attr(4111,root,root) %{_bindir}/lxc-unshare
>
> === modified file 'src/lxc/Makefile.am'
> --- src/lxc/Makefile.am	2011-03-10 07:25:34 +0000
> +++ src/lxc/Makefile.am	2011-03-30 15:36:58 +0000
> @@ -72,6 +72,7 @@
>   	lxc-setuid \
>   	lxc-version \
>   	lxc-create \
> +	lxc-clone \
>   	lxc-destroy
>
>   bin_PROGRAMS = \
>
> === modified file 'src/lxc/Makefile.in'

Makefile.in is generated. I suppose it is the diff command which 
integrated the configure and Makefile.in in the diff result.

> === added file 'src/lxc/lxc-clone.in'
> --- src/lxc/lxc-clone.in	1970-01-01 00:00:00 +0000
> +++ src/lxc/lxc-clone.in	2011-03-30 15:36:58 +0000
> @@ -0,0 +1,206 @@
> +#!/bin/bash
> +
> +#
> +# lxc: linux Container library
> +
> +# Authors:
> +# Serge Hallyn<serge.hallyn at ubuntu.com>
> +# Daniel Lezcano<daniel.lezcano at free.fr>
> +
> +# This library is free software; you can redistribute it and/or
> +# modify it under the terms of the GNU Lesser General Public
> +# License as published by the Free Software Foundation; either
> +# version 2.1 of the License, or (at your option) any later version.
> +
> +# This library is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +# Lesser General Public License for more details.
> +
> +# You should have received a copy of the GNU Lesser General Public
> +# License along with this library; if not, write to the Free Software
> +# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> +
> +usage() {
> +    echo "usage: lxc-clone -o<orig>  -n<new>  [-s] [-h] [-L fssize] [-v vgname]"
> +}
> +
> +help() {
> +    usage
> +    echo
> +    echo "creates a lxc system object."
> +    echo
> +    echo "Options:"
> +    echo "orig        : name of the original container"
> +    echo "new         : name of the new container"
> +    echo "-s          : make the new rootfs a snapshot of the original"
> +    echo "fssize      : size if creating a new fs.  By default, 2G"
> +    echo "vgname      : lvm volume group name, lxc by default"
> +}
> +
> +shortoptions='ho:n:sL:v:'
> +longoptions='help,orig:,name:,snapshot,fssize,vgname'
> +lxc_path=/var/lib/lxc
> +bindir=/usr/bin
> +snapshot=no
> +lxc_size=2G
> +lxc_vg=lxc
> +
> +getopt=$(getopt -o $shortoptions --longoptions  $longoptions -- "$@")
> +if [ $? != 0 ]; then
> +    usage
> +    exit 1;
> +fi
> +
> +eval set -- "$getopt"
> +
> +while true; do
> +        case "$1" in
> +	    -h|--help)
> +		help
> +		exit 1
> +		;;
> +	    -s|--snapshot)
> +		shift
> +		snapshot=yes
> +		;;
> +	    -o|--orig)
> +		shift
> +		lxc_orig=$1
> +		shift
> +		;;
> +	    -L|--fssize)
> +		shift
> +		lxc_size=$1
> +		shift
> +		;;
> +	    -v|--vgname)
> +		shift
> +		lxc_vg=$1
> +		shift
> +		;;
> +	    -n|--new)
> +		shift
> +		lxc_new=$1
> +		shift
> +		;;
> +            --)
> +		shift
> +		break;;
> +            *)
> +		echo $1
> +		usage
> +		exit 1
> +		;;
> +        esac
> +done
> +
> +if [ -z "$lxc_path" ]; then
> +    echo "no configuration path defined !"
> +    exit 1
> +fi
> +
> +if [ ! -r $lxc_path ]; then
> +    echo "configuration path '$lxc_path' not found"
> +    exit 1
> +fi
> +
> +if [ -z "$lxc_orig" ]; then
> +    echo "no original container name specified"
> +    usage
> +    exit 1
> +fi
> +
> +if [ -z "$lxc_new" ]; then
> +    echo "no new container name specified"
> +    usage
> +    exit 1
> +fi
> +
> +if [ "$(id -u)" != "0" ]; then
> +   echo "This command has to be run as root"
> +   exit 1
> +fi
> +
> +if [ ! -r $lxc_path ]; then
> +    echo "no configuration path defined !"
> +    exit 1
> +fi
> +
> +if [ ! -d "$lxc_path/$lxc_orig" ]; then
> +    echo "'$lxc_orig' does not exist"
> +    exit 1
> +fi
> +
> +if [ -d "$lxc_path/$lxc_new" ]; then
> +    echo "'$lxc_new' already exists"
> +    exit 1
> +fi
> +
> +trap "${bindir}/lxc-destroy -n $lxc_new; echo aborted; exit 1" SIGHUP SIGINT SIGTERM
> +
> +mkdir -p $lxc_path/$lxc_new
> +
> +echo "Tweaking configuration"
> +cp $lxc_path/$lxc_orig/config $lxc_path/$lxc_new/config
> +sed -i '/lxc.utsname/d' $lxc_path/$lxc_new/config
> +echo "lxc.utsname = $hostname">>  $lxc_path/$lxc_new/config

We should not assume lxc.utsname is in the configuration file in order 
to not write a hostname in all the cases.
The user may want to let the container to setup itself the hostname.

> +
> +sed -i '/lxc.mount/d' $lxc_path/$lxc_new/config
> +echo "lxc.mount = $lxc_path/$lxc_new/fstab">>  $lxc_path/$lxc_new/config
> +
> +cp $lxc_path/$lxc_orig/fstab $lxc_path/$lxc_new/fstab
> +sed -i "s@$lxc_path/$lxc_orig@$lxc_path/$lxc_new@" $lxc_path/$lxc_new/fstab

Same comment.

> +echo "Copying rootfs..."
> +rootfs=$lxc_path/$lxc_new/rootfs
> +# First figure out if the old is a device.  For now we only support
> +# lvm devices.
> +mounted=0
> +sed -i '/lxc.rootfs/d' $lxc_path/$lxc_new/config
> +oldroot=`grep lxc.rootfs $lxc_path/$lxc_orig/config | awk -F= '{ print $2 '}`
> +if [ -b $oldroot ]; then
> +	# this is a device.  If we don't want to snapshot, then mkfs, mount
> +	# and rsync.  Trivial but not yet implemented
> +	if [ $snapshot == "no" ]; then
> +		echo "non-snapshot and non-lvm clone of block device not yet implemented"
> +		exit 1
> +	fi
> +	lvdisplay $oldroot>  /dev/null 2>&1
> +	if [ $? -ne 0 ]; then
> +		echo "non-snapshot and non-lvm clone of block device not yet implemented"
> +		exit 1
> +	fi
> +	# ok, create a snapshot of the lvm device
> +	lvcreate -s -L $lxc_size -n $lxc_new /dev/$lxc_vg/$lxc_orig || exit 1
> +	echo "lxc.rootfs = /dev/$lxc_vg/$lxc_new">>  $lxc_path/$lxc_new/config
> +	# and mount it so we can tweak it
> +	mkdir -p $lxc_path/$lxc_new/rootfs
> +	mount /dev/$lxc_vg/$lxc_new $rootfs || { echo "failed to mount new rootfs"; exit 1; }
> +	mounted=1
> +else
> +	cp -a $lxc_path/$lxc_orig/rootfs $lxc_path/$lxc_new/rootfs || return 1
> +	echo "lxc.rootfs = $rootfs">>  $lxc_path/$lxc_new/config
> +fi
> +
> +echo "Updating rootfs..."
> +hostname=$lxc_new
> +
> +# so you can 'ssh $hostname.' or 'ssh $hostname.local'
> +sed -i "s/send host-name.*$/send host-name $hostname/" $rootfs/etc/dhcp/dhclient.conf
> +
> +# set the hostname
> +cat<<EOF>  $rootfs/etc/hostname
> +$hostname
> +EOF
> +# set minimal hosts
> +cat<<EOF>  $rootfs/etc/hosts
> +127.0.0.1 localhost $hostname
> +EOF
> +
> +# if this was a block device, then umount it now
> +if [ $mounted -eq 1 ]; then
> +	umount $rootfs
> +fi
> +
> +echo "'$lxc_new' created"
>
> === modified file 'src/lxc/lxc-destroy.in'
> --- src/lxc/lxc-destroy.in	2010-01-10 10:40:21 +0000
> +++ src/lxc/lxc-destroy.in	2011-03-29 23:00:34 +0000
> @@ -26,7 +26,8 @@
>   #
>
>   usage() {
> -    echo "usage: $0 -n<name>"
> +    echo "usage: $0 -n<name>  [-l]"
> +    echo "       if -l is specified, attempt to lvremove the rootfs device"
>   }
>
>   if [ "$(id -u)" != "0" ]; then
> @@ -34,9 +35,9 @@
>      exit 1
>   fi
>
> -shortoptions='n:'
> -longoptions='name:'
> -lxc_path=@LXCPATH@
> +shortoptions='n:l'
> +longoptions='name:,lvm'
> +lxc_path=/var/lib/lxc
>
>   getopt=$(getopt -o $shortoptions --longoptions  $longoptions -- "$@")
>   if [ $? != 0 ]; then
> @@ -46,6 +47,8 @@
>
>   eval set -- "$getopt"
>
> +lvremove=0
> +
>   while true; do
>           case "$1" in
>   	    -n|--name)
> @@ -53,6 +56,10 @@
>   		lxc_name=$1
>   		shift
>   		;;
> +	    -l|--lvm)
> +		shift
> +		lvremove=1
> +		;;
>               --)
>   		shift
>   		break;;
> @@ -75,5 +82,13 @@
>       exit 1
>   fi
>
> +if [ $lvremove -eq 1 ]; then
> +    rootdev=`grep lxc.rootfs $lxc_path/$lxc_name/config | awk -F= '{ print $2 '}`
> +    # only makes sense if it is a blockdev or a symlink to one
> +    if [ -b $rootdev -o -h $rootdev ]; then
> +	    lvremove $rootdev
> +    fi
> +fi
> +
>   # recursively remove the container to remove old container configuration
>   rm -rf --preserve-root $lxc_path/$lxc_name