1，lxc介绍
容器是一种轻量级的虚拟化技术，与qemu/kvm、VMware、Xen等完全的虚拟化方案相比，LXC更像是加强的“chroot”，因为LXC不但没有没有对硬件设备进行仿真，而且可以与主机共享一模一样的操作系统，所以LXC与solaris的zones和BSD的jails相比，更具优势。
目前，有两个比较方便的管理容器的用户空间的工具：libvirt和lxc。libvirt通过"lxc:///"像管理其他虚拟机驱动一样管理lxc虚拟机。另一个是与libvirt完全独立的LXC，它定义了一些列的命令，可以更灵活的管理和使用lxc。
下面，将以LXC为例来介绍lxc的使用。
2，LXC的安装和使用
（1）LXC的安装
sudo apt-get install lxc
该命令将自动安装LXC依赖的其他软件：cgroup-lite, lvm2, and debootstrap。如果想使用libvirt来实现lxc的管理，还需要安装 libvirt-bin和libvirt-lxc。
（2）LXC主机端的配置文件介绍
在使用LXC之前，首先对其配置文件进行简单的介绍，以便使大家能更好的理解LXC的工作原理。
a. /etc/lxc/lxc.conf
容器默认的配置文件，如果在创建lxc容器的时候不指定配置文件，将默认使用这个配置文件。主要针 对网络以及命名空间的配置。还有一些其他的配置例子可以在/usr/share/doc/lxc/examples/目录下找到。
b. /usr/lib/lxc/templates/
该目录下保存了当前LXC支持的各种发行版的linux的模板配置文件，目前主要有:
lxc-Ubuntu, lxc-Fedora,lxc-openSUSE,lxc-debian,lxc-busybox,lxc-sshd,lxc-cloud-ubuntu等。
c. /var/lib/lxc
每个容器的实例存放在这个目录下。
d. /var/cache/lxc
容器实例的cache，当用户创建一种类型的实例后，将会在此目录下cache，再次创建时将不需要从网 上下载，直接采用cache的版本，加速了容器实例的创建过程。
下面来分析下lxc-ubuntu的创建过程（详见最下面的注释说明）：
#!/bin/bash
#
# template script for generating ubuntu container for LXC
#
# This script consolidates and extends the existing lxc ubuntu scripts
#
# Copyright ?2011 Serge Hallyn <serge.hallyn@canonical.com>
# Copyright ?2010 Wilhelm Meier
# Author: Wilhelm Meier <wilhelm.meier@fh-kl.de>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2, as
# published by the Free Software Foundation.
# This program 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 General Public License for more details.
# You should have received a copy of the GNU General Public License along
# with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
#
set -e ##如果命令带非零值返回,立即退出
if [ -r /etc/default/lxc ]; then
. /etc/default/lxc #导入一些环境变量
fi
configure_ubuntu()
{
rootfs=$1
hostname=$2
release=$3
# configure the network using the dhcp
cat <<EOF > $rootfs/etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp
EOF
# set the hostname
cat <<EOF > $rootfs/etc/hostname
$hostname
EOF
# set minimal hosts
cat <<EOF > $rootfs/etc/hosts
127.0.0.1 localhost
127.0.1.1 $hostname
# The following lines are desirable for IPv6 capable hosts
::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
EOF
if [ ! -f $rootfs/etc/init/container-detect.conf ]; then
# suppress log level output for udev
sed -i "s/=\"err\"/=0/" $rootfs/etc/udev/udev.conf
# remove jobs for consoles 5 and 6 since we only create 4 consoles in
# this template
rm -f $rootfs/etc/init/tty{5,6}.conf
fi
if [ -z "$bindhome" ]; then
chroot $rootfs useradd --create-home -s /bin/bash ubuntu
echo "ubuntu:ubuntu" | chroot $rootfs chpasswd
fi
return 0
}
# finish setting up the user in the container by injecting ssh key and
# adding sudo group membership.
# passed-in user is either 'ubuntu' or the user to bind in from host.
finalize_user()
{
user=$1
sudo_version=$(chroot $rootfs dpkg-query -W -f='${Version}' sudo)
if chroot $rootfs dpkg --compare-versions $sudo_version gt "1.8.3p1-1"; then
groups="sudo"
else
groups="sudo admin"
fi
for group in $groups; do
chroot $rootfs groupadd --system $group >/dev/null 2>&1 || true
chroot $rootfs adduser ${user} $group >/dev/null 2>&1 || true
done
if [ -n "$auth_key" -a -f "$auth_key" ]; then
u_path="/home/${user}/.ssh"
root_u_path="$rootfs/$u_path"
mkdir -p $root_u_path
cp $auth_key "$root_u_path/authorized_keys"
chroot $rootfs chown -R ${user}: "$u_path"
echo "Inserted SSH public key from $auth_key into /home/${user}/.ssh/authorized_keys"
fi
return 0
}
write_sourceslist()
{
# $1 => path to the rootfs
# $2 => architecture we want to add
# $3 => whether to use the multi-arch syntax or not
case $2 in
amd64|i386)
MIRROR=${MIRROR:-http://archive.ubuntu.com/ubuntu}
SECURITY_MIRROR=${SECURITY_MIRROR:-http://security.ubuntu.com/ubuntu}
;;
*)
MIRROR=${MIRROR:-http://ports.ubuntu.com/ubuntu-ports}
SECURITY_MIRROR=${SECURITY_MIRROR:-http://ports.ubuntu.com/ubuntu-ports}
;;
esac
if [ -n "$3" ]; then
cat >> "$1/etc/apt/sources.list" << EOF
deb [arch=$2] $MIRROR ${release} main restricted universe multiverse
deb [arch=$2] $MIRROR ${release}-updates main restricted universe multiverse
deb [arch=$2] $SECURITY_MIRROR ${release}-security main restricted universe multiverse
EOF
else
cat >> "$1/etc/apt/sources.list" << EOF
deb $MIRROR ${release} main restricted universe multiverse
deb $MIRROR ${release}-updates main restricted universe multiverse
deb $SECURITY_MIRROR ${release}-security main restricted universe multiverse
EOF
fi
}
download_ubuntu()
{
cache=$1
arch=$2
release=$3
packages=vim,ssh
echo "installing packages: $packages"
# check the mini ubuntu was not already downloaded
mkdir -p "$cache/partial-$arch"
if [ $? -ne 0 ]; then
echo "Failed to create '$cache/partial-$arch' directory"
return 1
fi
# download a mini ubuntu into a cache
echo "Downloading ubuntu $release minimal ..."
if [ -n "$(which qemu-debootstrap)" ]; then
qemu-debootstrap --verbose --components=main,universe --arch=$arch --include=$packages $release $cache/partial-$arch $MIRROR
else
debootstrap --verbose --components=main,universe --arch=$arch --include=$packages $release $cache/partial-$arch $MIRROR ##在这里下载制定的linux发行版
fi
if [ $? -ne 0 ]; then
echo "Failed to download the rootfs, aborting."
return 1
fi
# Serge isn't sure whether we should avoid doing this when
# $release == `distro-info -d`
echo "Installing updates"
> $cache/partial-$arch/etc/apt/sources.list
write_sourceslist $cache/partial-$arch/ $arch ##下载完成后，修改source.lst文件，升级和安装软件做准备
##改变系统的根目录，执行update，因为，要用新的source.lst
chroot "$1/partial-${arch}" apt-get update
if [ $? -ne 0 ]; then
echo "Failed to update the apt cache"
return 1
fi
cat > "$1/partial-${arch}"/usr/sbin/policy-rc.d << EOF
#!/bin/sh
exit 101
EOF
chmod +x "$1/partial-${arch}"/usr/sbin/policy-rc.d
lxc-unshare -s MOUNT -- chroot "$1/partial-${arch}" apt-get dist-upgrade -y
ret=$?
rm -f "$1/partial-${arch}"/usr/sbin/policy-rc.d
if [ $ret -ne 0 ]; then
echo "Failed to upgrade the cache"
return 1
fi
mv "$1/partial-$arch" "$1/rootfs-$arch"
echo "Download complete"
return 0
}
copy_ubuntu()
{
cache=$1
arch=$2
rootfs=$3
# make a local copy of the miniubuntu
echo "Copying rootfs to $rootfs ..."
mkdir -p $rootfs
#使用rsync进行镜像的备份，实际相当于镜像的拷贝
rsync -a $cache/rootfs-$arch/ $rootfs/ || return 1
return 0
}
install_ubuntu()
{
rootfs=$1
release=$2
flushcache=$3
cache="/var/cache/lxc/$release"
mkdir -p /var/lock/subsys/
(
flock -x 200
if [ $? -ne 0 ]; then
echo "Cache repository is busy."
return 1
fi
if [ $flushcache -eq 1 ]; then
echo "Flushing cache..."
rm -rf "$cache/partial-$arch"
rm -rf "$cache/rootfs-$arch"
fi
echo "Checking cache download in $cache/rootfs-$arch ... "
if [ ! -e "$cache/rootfs-$arch" ]; then
download_ubuntu $cache $arch $release ##下载指定版本的系统到cache目录下
if [ $? -ne 0 ]; then
echo "Failed to download 'ubuntu $release base'"
return 1
fi
fi
echo "Copy $cache/rootfs-$arch to $rootfs ... "
copy_ubuntu $cache $arch $rootfs ##从cache目录下拷贝到真正的根目录下
if [ $? -ne 0 ]; then
echo "Failed to copy rootfs"
return 1
fi
return 0
) 200>/var/lock/subsys/lxc
return $?
}
copy_configuration()
{
path=$1
rootfs=$2
name=$3
arch=$4
release=$5
if [ $arch = "i386" ]; then
arch="i686"
fi
ttydir=""
if [ -f $rootfs/etc/init/container-detect.conf ]; then
ttydir=" lxc"
fi
# if there is exactly one veth network entry, make sure it has an
# associated hwaddr.
nics=`grep -e '^lxc\.network\.type[ \t]*=[ \t]*veth' $path/config | wc -l`
if [ $nics -eq 1 ]; then
grep -q "^lxc.network.hwaddr" $path/config || cat <<EOF >> $path/config
lxc.network.hwaddr = 00:16:3e:$(openssl rand -hex 3| sed 's/\(..\)/\1:/g; s/.$//')
EOF
fi
cat <<EOF >> $path/config
lxc.utsname = $name
lxc.devttydir =$ttydir
lxc.tty = 4
lxc.pts = 1024
lxc.rootfs = $rootfs
lxc.mount = $path/fstab
lxc.arch = $arch
lxc.cap.drop = sys_module mac_admin
lxc.pivotdir = lxc_putold
# uncomment the next line to run the container unconfined:
#lxc.aa_profile = unconfined
lxc.cgroup.devices.deny = a
# Allow any mknod (but not using the node)
lxc.cgroup.devices.allow = c *:* m
lxc.cgroup.devices.allow = b *:* m
# /dev/null and zero
lxc.cgroup.devices.allow = c 1:3 rwm
lxc.cgroup.devices.allow = c 1:5 rwm
# consoles
lxc.cgroup.devices.allow = c 5:1 rwm
lxc.cgroup.devices.allow = c 5:0 rwm
#lxc.cgroup.devices.allow = c 4:0 rwm
#lxc.cgroup.devices.allow = c 4:1 rwm
# /dev/{,u}random
lxc.cgroup.devices.allow = c 1:9 rwm
lxc.cgroup.devices.allow = c 1:8 rwm
lxc.cgroup.devices.allow = c 136:* rwm
lxc.cgroup.devices.allow = c 5:2 rwm
# rtc
lxc.cgroup.devices.allow = c 254:0 rwm
#fuse
lxc.cgroup.devices.allow = c 10:229 rwm
#tun
lxc.cgroup.devices.allow = c 10:200 rwm
#full
lxc.cgroup.devices.allow = c 1:7 rwm
#hpet
lxc.cgroup.devices.allow = c 10:228 rwm
#kvm
lxc.cgroup.devices.allow = c 10:232 rwm
EOF
cat <<EOF > $path/fstab
proc proc proc nodev,noexec,nosuid 0 0
sysfs sys sysfs defaults 0 0
EOF
if [ $? -ne 0 ]; then
echo "Failed to add configuration"
return 1
fi
return 0
}
trim()
{
rootfs=$1
release=$2
# provide the lxc service
cat <<EOF > $rootfs/etc/init/lxc.conf
# fake some events needed for correct startup other services
description "Container Upstart"
start on startup
script
rm -rf /var/run/*.pid
rm -rf /var/run/network/*
/sbin/initctl emit stopped JOB=udevtrigger --no-wait
/sbin/initctl emit started JOB=udev --no-wait
end script
EOF
# fix buggus runlevel with sshd
cat <<EOF > $rootfs/etc/init/ssh.conf
# ssh - OpenBSD Secure Shell server
#
# The OpenSSH server provides secure shell access to the system.
description "OpenSSH server"
start on filesystem
stop on runlevel [!2345]
expect fork
respawn
respawn limit 10 5
umask 022
# replaces SSHD_OOM_ADJUST in /etc/default/ssh
oom never
pre-start script
test -x /usr/sbin/sshd || { stop; exit 0; }
test -e /etc/ssh/sshd_not_to_be_run && { stop; exit 0; }
test -c /dev/null || { stop; exit 0; }
mkdir -p -m0755 /var/run/sshd
end script
# if you used to set SSHD_OPTS in /etc/default/ssh, you can change the
# 'exec' line here instead
exec /usr/sbin/sshd
EOF
cat <<EOF > $rootfs/etc/init/console.conf
# console - getty
#
# This service maintains a console on tty1 from the point the system is
# started until it is shut down again.
start on stopped rc RUNLEVEL=[2345]
stop on runlevel [!2345]
respawn
exec /sbin/getty -8 38400 /dev/console
EOF
cat <<EOF > $rootfs/lib/init/fstab
# /lib/init/fstab: cleared out for bare-bones lxc
EOF
# reconfigure some services
if [ -z "$LANG" ]; then
chroot $rootfs locale-gen en_US.UTF-8
chroot $rootfs update-locale LANG=en_US.UTF-8
else
chroot $rootfs locale-gen $LANG
chroot $rootfs update-locale LANG=$LANG
fi
# remove pointless services in a container
chroot $rootfs /usr/sbin/update-rc.d -f ondemand remove
chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls u*.conf); do mv $f $f.orig; done'
chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls tty[2-9].conf); do mv $f $f.orig; done'
chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls plymouth*.conf); do mv $f $f.orig; done'
chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls hwclock*.conf); do mv $f $f.orig; done'
chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls module*.conf); do mv $f $f.orig; done'
# if this isn't lucid, then we need to twiddle the network upstart bits :(
if [ $release != "lucid" ]; then
sed -i 's/^.*emission handled.*$/echo Emitting lo/' $rootfs/etc/network/if-up.d/upstart
fi
}
post_process()
{
rootfs=$1
release=$2
trim_container=$3
if [ $trim_container -eq 1 ]; then
trim $rootfs $release
elif [ ! -f $rootfs/etc/init/container-detect.conf ]; then
# Make sure we have a working resolv.conf
cresolvonf="${rootfs}/etc/resolv.conf"
mv $cresolvonf ${cresolvonf}.lxcbak
cat /etc/resolv.conf > ${cresolvonf}
# for lucid, if not trimming, then add the ubuntu-virt
# ppa and install lxcguest
if [ $release = "lucid" ]; then
chroot $rootfs apt-get install --force-yes -y python-software-properties
chroot $rootfs add-apt-repository ppa:ubuntu-virt/ppa
fi
chroot $rootfs apt-get update
chroot $rootfs apt-get install --force-yes -y lxcguest
# Restore old resolv.conf
rm -f ${cresolvonf}
mv ${cresolvonf}.lxcbak ${cresolvonf}
fi
# If the container isn't running a native architecture, setup multiarch
if [ -x "$(ls -1 ${rootfs}/usr/bin/qemu-*-static 2>/dev/null)" ]; then
dpkg_version=$(chroot $rootfs dpkg-query -W -f='${Version}' dpkg)
if chroot $rootfs dpkg --compare-versions $dpkg_version ge "1.16.2"; then
chroot $rootfs dpkg --add-architecture ${hostarch}
else
mkdir -p ${rootfs}/etc/dpkg/dpkg.cfg.d
echo "foreign-architecture ${hostarch}" > ${rootfs}/etc/dpkg/dpkg.cfg.d/lxc-multiarch
fi
# Save existing value of MIRROR and SECURITY_MIRROR
DEFAULT_MIRROR=$MIRROR
DEFAULT_SECURITY_MIRROR=$SECURITY_MIRROR
# Write a new sources.list containing both native and multiarch entries
> ${rootfs}/etc/apt/sources.list
write_sourceslist $rootfs $arch "native"
MIRROR=$DEFAULT_MIRROR
SECURITY_MIRROR=$DEFAULT_SECURITY_MIRROR
write_sourceslist $rootfs $hostarch "multiarch"
# Finally update the lists and install upstart using the host architecture
chroot $rootfs apt-get update
chroot $rootfs apt-get install --force-yes -y --no-install-recommends upstart:${hostarch} mountall:${hostarch} iproute:${hostarch} isc-dhcp-client:${hostarch}
fi
# rmdir /dev/shm for containers that have /run/shm
# I'm afraid of doing rm -rf $rootfs/dev/shm, in case it did
# get bind mounted to the host's /run/shm. So try to rmdir
# it, and in case that fails move it out of the way.
if [ -d $rootfs/run/shm ]; then
[ -d "$rootfs/dev/shm" ] && rmdir $rootfs/dev/shm
[ -e "$rootfs/dev/shm" ] && mv $rootfs/dev/shm $rootfs/dev/shm.bak
ln -s /run/shm $rootfs/dev/shm
fi
}
do_bindhome()
{
rootfs=$1
user=$2
# copy /etc/passwd, /etc/shadow, and /etc/group entries into container
pwd=`getent passwd $user` || { echo "Failed to copy password entry for $user"; false; }
echo $pwd >> $rootfs/etc/passwd
# make sure user's shell exists in the container
shell=`echo $pwd | cut -d: -f 7`
if [ ! -x $rootfs/$shell ]; then
echo "shell $shell for user $user was not found in the container."
pkg=`dpkg -S $(readlink -m $shell) | cut -d ':' -f1`
echo "Installing $pkg"
chroot $rootfs apt-get --force-yes -y install $pkg
fi
shad=`getent shadow $user`
echo "$shad" >> $rootfs/etc/shadow
# bind-mount the user's path into the container's /home
h=`getent passwd $user | cut -d: -f 6`
mkdir -p $rootfs/$h
# use relative path in container
h2=${h#/}
while [ ${h2:0:1} = "/" ]; do
h2=${h2#/}
done
echo "$h $h2 none bind 0 0" >> $path/fstab
# Make sure the group exists in container
grp=`echo $pwd | cut -d: -f 4` # group number for $user
grpe=`getent group $grp` || return 0 # if host doesn't define grp, ignore in container
chroot $rootfs getent group "$grpe" || echo "$grpe" >> $rootfs/etc/group
}
usage()
{
cat <<EOF
$1 -h|--help [-a|--arch] [-b|--bindhome <user>] [--trim] [-d|--debug]
[-F | --flush-cache] [-r|--release <release>] [ -S | --auth-key <keyfile>]
release: the ubuntu release (e.g. precise): defaults to host release on ubuntu, otherwise uses latest LTS
trim: make a minimal (faster, but not upgrade-safe) container
bindhome: bind <user>'s home into the container
The ubuntu user will not be created, and <user> will have
sudo access.
arch: the container architecture (e.g. amd64): defaults to host arch
auth-key: SSH Public key file to inject into container
EOF
return 0
}
options=$(getopt -o a:b:hp:r:xn:FS:d -l arch:,bindhome:,help,path:,release:,trim,name:,flush-cache,auth-key:,debug -- "$@")
if [ $? -ne 0 ]; then
usage $(basename $0)
exit 1
fi
eval set -- "$options"
release=precise # Default to the last Ubuntu LTS release for non-Ubuntu systems
if [ -f /etc/lsb-release ]; then
. /etc/lsb-release
if [ "$DISTRIB_ID" = "Ubuntu" ]; then
release=$DISTRIB_CODENAME
fi
fi
bindhome=
arch=$(arch)
# Code taken from debootstrap
if [ -x /usr/bin/dpkg ] && /usr/bin/dpkg --print-architecture >/dev/null 2>&1; then
arch=`/usr/bin/dpkg --print-architecture`
elif type udpkg >/dev/null 2>&1 && udpkg --print-architecture >/dev/null 2>&1; then
arch=`/usr/bin/udpkg --print-architecture`
else
arch=$(arch)
if [ "$arch" = "i686" ]; then
arch="i386"
elif [ "$arch" = "x86_64" ]; then
arch="amd64"
elif [ "$arch" = "armv7l" ]; then
arch="armel"
fi
fi
debug=0
trim_container=0
hostarch=$arch
flushcache=0
while true
do
case "$1" in
-h|--help) usage $0 && exit 0;;
-p|--path) path=$2; shift 2;;
-n|--name) name=$2; shift 2;;
-F|--flush-cache) flushcache=1; shift 1;;
-r|--release) release=$2; shift 2;;
-b|--bindhome) bindhome=$2; shift 2;;
-a|--arch) arch=$2; shift 2;;
-x|--trim) trim_container=1; shift 1;;
-S|--auth-key) auth_key=$2; shift 2;;
-d|--debug) debug=1; shift 1;;
--) shift 1; break ;;
*) break ;;
esac
done
if [ $debug -eq 1 ]; then
set -x
fi
if [ -n "$bindhome" ]; then
pwd=`getent passwd $bindhome`
if [ $? -ne 0 ]; then
echo "Error: no password entry found for $bindhome"
exit 1
fi
fi
if [ "$arch" == "i686" ]; then
arch=i386
fi
if [ $hostarch = "i386" -a $arch = "amd64" ]; then
echo "can't create amd64 container on i386"
exit 1
fi
type debootstrap
if [ $? -ne 0 ]; then
echo "'debootstrap' command is missing"
exit 1
fi
if [ -z "$path" ]; then
echo "'path' parameter is required"
exit 1
fi
if [ "$(id -u)" != "0" ]; then
echo "This script should be run as 'root'"
exit 1
fi
rootfs=$path/rootfs
##执行的第一个操作，rootfs文件系统挂载点，flushcache创建cache的目录，release创建实例的版本
install_ubuntu $rootfs $release $flushcache
if [ $? -ne 0 ]; then
echo "failed to install ubuntu $release"
exit 1
fi
configure_ubuntu $rootfs $name $release ##将镜像从cache拷贝到 正的rootfs
if [ $? -ne 0 ]; then
echo "failed to configure ubuntu $release for a container"
exit 1
fi
copy_configuration $path $rootfs $name $arch $release ##在根目录下生成config文件，并在fstab中挂载/proc和/fs
if [ $? -ne 0 ]; then
echo "failed write configuration file"
exit 1
fi
##配置resolv.conf,并在新生成的镜像中安装一些必要的软件，如：lxcguest
post_process $rootfs $release $trim_container
if [ -n "$bindhome" ]; then
do_bindhome $rootfs $bindhome
finalize_user $bindhome
else
finalize_user ubuntu ##创建用户/属组，配置ssh用户名和密码
fi
echo ""
echo "##"
echo "# The default user is 'ubuntu' with password 'ubuntu'!"
echo "# Use the 'sudo' command to run tasks as root in the container."
echo "##"
echo ""
lxc创建ubuntu虚拟机的详细过程参见上面注释！