Linux容器技術-lxc創建虛擬機的執行過程分析

1. lxc介紹

容器是一種輕量級的虛擬化技術，與qemu/kvm、VMware、Xen等完全的虛擬化方案相比，LXC更像是加強的“chroot”，因為LXC不但沒有沒有對硬件設備進行仿真，而且可以與主機共享一模一樣的操作系統，所以LXC與solaris的zones和BSD的jails相比，更具優勢。

目前，有兩個比較方便的管理容器的用戶空間的工具：libvirt和lxc。libvirt通過"lxc:///"像管理其他虛擬機驅動一樣管理lxc虛擬機。另一個是與libvirt完全獨立的LXC，它定義了一些列的命令，可以更靈活的管理和使用lxc。

下面，將以LXC為例來介紹lxc的使用。

2 LXC的安裝和使用

（1）LXC的安裝

1. sudo apt-get install lxc

該命令將自動安裝LXC依賴的其他軟件：cgroup-lite, lvm2, and debootstrap。如果想使用libvirt來實現lxc的管理，還需要安裝 libvirt-bin和libvirt-lxc。 （2）LXC主機端的配置文件介紹 在使用LXC之前，首先對其配置文件進行簡單的介紹，以便使大家能更好的理解LXC的工作原理。 a. /etc/lxc/lxc.conf 容器默認的配置文件，如果在創建lxc容器的時候不指定配置文件，將默認使用這個配置文件。主要針 對網絡以及命名空間的配置。還有一些其他的配置例子可以在/usr/share/doc/lxc/examples/目錄下 找到。 b. /usr/lib/lxc/templates/ 該目錄下保存了當前LXC支持的各種發行版的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 每個容器的實例存放在這個目錄下。 d. /var/cache/lxc 容器實例的cache，當用戶創建一種類型的實例後，將會在此目錄下cache，再次創建時將不需要從網 上下載，直接采用cache的版本，加速了容器實例的創建過程。
下面來分析下lxc-ubuntu的創建過程（詳見最下面的注釋說明）：

1. #!/bin/bash
3. #
4. # template script for generating ubuntu container for LXC
5. #
6. # This script consolidates and extends the existing lxc ubuntu scripts
7. #
9. # Copyright ?2011 Serge Hallyn <[email protected]>
10. # Copyright ?2010 Wilhelm Meier
11. # Author: Wilhelm Meier <[email protected]>
12. #
13. # This program is free software; you can redistribute it and/or modify
14. # it under the terms of the GNU General Public License version 2, as
15. # published by the Free Software Foundation.
17. # This program is distributed in the hope that it will be useful,
18. # but WITHOUT ANY WARRANTY; without even the implied warranty of
19. # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20. # GNU General Public License for more details.
22. # You should have received a copy of the GNU General Public License along
23. # with this program; if not, write to the Free Software Foundation, Inc.,
24. # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
25. #
27. set -e ##如果命令帶非零值返回,立即退出
29. if [ -r /etc/default/lxc ]; then
30. . /etc/default/lxc #導入一些環境變量
31. fi
33. configure_ubuntu()
34. {
35. rootfs=$1
36. hostname=$2
37. release=$3
39. # configure the network using the dhcp
40. cat <<EOF > $rootfs/etc/network/interfaces
41. # This file describes the network interfaces available on your system
42. # and how to activate them. For more information, see interfaces(5).
44. # The loopback network interface
45. auto lo
46. iface lo inet loopback
48. auto eth0
49. iface eth0 inet dhcp
50. EOF
52. # set the hostname
53. cat <<EOF > $rootfs/etc/hostname
54. $hostname
55. EOF
56. # set minimal hosts
57. cat <<EOF > $rootfs/etc/hosts
58. 127.0.0.1 localhost
59. 127.0.1.1 $hostname
61. # The following lines are desirable for IPv6 capable hosts
62. ::1 ip6-localhost ip6-loopback
63. fe00::0 ip6-localnet
64. ff00::0 ip6-mcastprefix
65. ff02::1 ip6-allnodes
66. ff02::2 ip6-allrouters
67. EOF
69. if [ ! -f $rootfs/etc/init/container-detect.conf ]; then
70. # suppress log level output for udev
71. sed -i "s/=\"err\"/=0/" $rootfs/etc/udev/udev.conf
73. # remove jobs for consoles 5 and 6 since we only create 4 consoles in
74. # this template
75. rm -f $rootfs/etc/init/tty{5,6}.conf
76. fi
78. if [ -z "$bindhome" ]; then
79. chroot $rootfs useradd --create-home -s /bin/bash ubuntu
80. echo "ubuntu:ubuntu" | chroot $rootfs chpasswd
81. fi
83. return 0
84. }
86. # finish setting up the user in the container by injecting ssh key and
87. # adding sudo group membership.
88. # passed-in user is either 'ubuntu' or the user to bind in from host.
89. finalize_user()
90. {
91. user=$1
93. sudo_version=$(chroot $rootfs dpkg-query -W -f='${Version}' sudo)
95. if chroot $rootfs dpkg --compare-versions $sudo_version gt "1.8.3p1-1"; then
96. groups="sudo"
97. else
98. groups="sudo admin"
99. fi
101. for group in $groups; do
102. chroot $rootfs groupadd --system $group >/dev/null 2>&1 || true
103. chroot $rootfs adduser ${user} $group >/dev/null 2>&1 || true
104. done
106. if [ -n "$auth_key" -a -f "$auth_key" ]; then
107. u_path="/home/${user}/.ssh"
108. root_u_path="$rootfs/$u_path"
110. mkdir -p $root_u_path
111. cp $auth_key "$root_u_path/authorized_keys"
112. chroot $rootfs chown -R ${user}: "$u_path"
114. echo "Inserted SSH public key from $auth_key into /home/${user}/.ssh/authorized_keys"
115. fi
116. return 0
117. }
119. write_sourceslist()
120. {
121. # $1 => path to the rootfs
122. # $2 => architecture we want to add
123. # $3 => whether to use the multi-arch syntax or not
125. case $2 in
126. amd64|i386)
127. MIRROR=${MIRROR:-http://archive.ubuntu.com/ubuntu}
128. SECURITY_MIRROR=${SECURITY_MIRROR:-http://security.ubuntu.com/ubuntu}
129. ;;
130. *)
131. MIRROR=${MIRROR:-http://ports.ubuntu.com/ubuntu-ports}
132. SECURITY_MIRROR=${SECURITY_MIRROR:-http://ports.ubuntu.com/ubuntu-ports}
133. ;;
134. esac
135. if [ -n "$3" ]; then
136. cat >> "$1/etc/apt/sources.list" << EOF
137. deb [arch=$2] $MIRROR ${release} main restricted universe multiverse
138. deb [arch=$2] $MIRROR ${release}-updates main restricted universe multiverse
139. deb [arch=$2] $SECURITY_MIRROR ${release}-security main restricted universe multiverse
140. EOF
141. else
142. cat >> "$1/etc/apt/sources.list" << EOF
143. deb $MIRROR ${release} main restricted universe multiverse
144. deb $MIRROR ${release}-updates main restricted universe multiverse
145. deb $SECURITY_MIRROR ${release}-security main restricted universe multiverse
146. EOF
147. fi
148. }
150. download_ubuntu()
151. {
152. cache=$1
153. arch=$2
154. release=$3
156. packages=vim,ssh
157. echo "installing packages: $packages"
159. # check the mini ubuntu was not already downloaded
160. mkdir -p "$cache/partial-$arch"
161. if [ $? -ne 0 ]; then
162. echo "Failed to create '$cache/partial-$arch' directory"
163. return 1
164. fi
166. # download a mini ubuntu into a cache
167. echo "Downloading ubuntu $release minimal ..."
168. if [ -n "$(which qemu-debootstrap)" ]; then
169. qemu-debootstrap --verbose --components=main,universe --arch=$arch --include=$packages $release $cache/partial-$arch $MIRROR
170. else
171. debootstrap --verbose --components=main,universe --arch=$arch --include=$packages $release $cache/partial-$arch $MIRROR ##在這裡下載制定的linux發行版
172. fi
174. if [ $? -ne 0 ]; then
175. echo "Failed to download the rootfs, aborting."
176. return 1
177. fi
179. # Serge isn't sure whether we should avoid doing this when
180. # $release == `distro-info -d`
181. echo "Installing updates"
182. > $cache/partial-$arch/etc/apt/sources.list
183. write_sourceslist $cache/partial-$arch/ $arch ##下載完成後，修改source.lst文件，升級和安裝軟件做准備
184. 
     
185. ##改變系統的根目錄，執行update，因為，要用新的source.lst

1. chroot "$1/partial-${arch}" apt-get update
2. if [ $? -ne 0 ]; then
3. echo "Failed to update the apt cache"
4. return 1
5. fi
6. cat > "$1/partial-${arch}"/usr/sbin/policy-rc.d << EOF
7. #!/bin/sh
8. exit 101
9. EOF
10. chmod +x "$1/partial-${arch}"/usr/sbin/policy-rc.d
12. lxc-unshare -s MOUNT -- chroot "$1/partial-${arch}" apt-get dist-upgrade -y
13. ret=$?
14. rm -f "$1/partial-${arch}"/usr/sbin/policy-rc.d
16. if [ $ret -ne 0 ]; then
17. echo "Failed to upgrade the cache"
18. return 1
19. fi
21. mv "$1/partial-$arch" "$1/rootfs-$arch"
22. echo "Download complete"
23. return 0
24. }
26. copy_ubuntu()
27. {
28. cache=$1
29. arch=$2
30. rootfs=$3
32. # make a local copy of the miniubuntu
33. echo "Copying rootfs to $rootfs ..."
34. mkdir -p $rootfs
35. #使用rsync進行鏡像的備份，實際相當於鏡像的拷貝
36. rsync -a $cache/rootfs-$arch/ $rootfs/ || return 1
37. return 0
38. }
40. install_ubuntu()
41. {
42. rootfs=$1
43. release=$2
44. flushcache=$3
45. cache="/var/cache/lxc/$release"
46. mkdir -p /var/lock/subsys/
48. (
49. flock -x 200
50. if [ $? -ne 0 ]; then
51. echo "Cache repository is busy."
52. return 1
53. fi
56. if [ $flushcache -eq 1 ]; then
57. echo "Flushing cache..."
58. rm -rf "$cache/partial-$arch"
59. rm -rf "$cache/rootfs-$arch"
60. fi
62. echo "Checking cache download in $cache/rootfs-$arch ... "
63. if [ ! -e "$cache/rootfs-$arch" ]; then
64. download_ubuntu $cache $arch $release ##下載指定版本的系統到cache目錄下
65. if [ $? -ne 0 ]; then
66. echo "Failed to download 'ubuntu $release base'"
67. return 1
68. fi
69. fi
71. echo "Copy $cache/rootfs-$arch to $rootfs ... "
72. copy_ubuntu $cache $arch $rootfs ##從cache目錄下拷貝到真正的根目錄下
73. if [ $? -ne 0 ]; then
74. echo "Failed to copy rootfs"
75. return 1
76. fi
78. return 0
80. ) 200>/var/lock/subsys/lxc
82. return $?
83. }
85. copy_configuration()
86. {
87. path=$1
88. rootfs=$2
89. name=$3
90. arch=$4
91. release=$5
93. if [ $arch = "i386" ]; then
94. arch="i686"
95. fi
97. ttydir=""
98. if [ -f $rootfs/etc/init/container-detect.conf ]; then
99. ttydir=" lxc"
100. fi
102. # if there is exactly one veth network entry, make sure it has an
103. # associated hwaddr.
104. nics=`grep -e '^lxc\.network\.type[ \t]*=[ \t]*veth' $path/config | wc -l`
105. if [ $nics -eq 1 ]; then
106. grep -q "^lxc.network.hwaddr" $path/config || cat <<EOF >> $path/config
107. lxc.network.hwaddr = 00:16:3e:$(openssl rand -hex 3| sed 's/\(..\)/\1:/g; s/.$//')
108. EOF
109. fi
111. cat <<EOF >> $path/config
112. lxc.utsname = $name
114. lxc.devttydir =$ttydir
115. lxc.tty = 4
116. lxc.pts = 1024
117. lxc.rootfs = $rootfs
118. lxc.mount = $path/fstab
119. lxc.arch = $arch
120. lxc.cap.drop = sys_module mac_admin
121. lxc.pivotdir = lxc_putold
123. # uncomment the next line to run the container unconfined:
124. #lxc.aa_profile = unconfined
126. lxc.cgroup.devices.deny = a
127. # Allow any mknod (but not using the node)
128. lxc.cgroup.devices.allow = c *:* m
129. lxc.cgroup.devices.allow = b *:* m
130. # /dev/null and zero
131. lxc.cgroup.devices.allow = c 1:3 rwm
132. lxc.cgroup.devices.allow = c 1:5 rwm
133. # consoles
134. lxc.cgroup.devices.allow = c 5:1 rwm
135. lxc.cgroup.devices.allow = c 5:0 rwm
136. #lxc.cgroup.devices.allow = c 4:0 rwm
137. #lxc.cgroup.devices.allow = c 4:1 rwm
138. # /dev/{,u}random
139. lxc.cgroup.devices.allow = c 1:9 rwm
140. lxc.cgroup.devices.allow = c 1:8 rwm
141. lxc.cgroup.devices.allow = c 136:* rwm
142. lxc.cgroup.devices.allow = c 5:2 rwm
143. # rtc
144. lxc.cgroup.devices.allow = c 254:0 rwm
145. #fuse
146. lxc.cgroup.devices.allow = c 10:229 rwm
147. #tun
148. lxc.cgroup.devices.allow = c 10:200 rwm
149. #full
150. lxc.cgroup.devices.allow = c 1:7 rwm
151. #hpet
152. lxc.cgroup.devices.allow = c 10:228 rwm
153. #kvm
154. lxc.cgroup.devices.allow = c 10:232 rwm
155. EOF
157. cat <<EOF > $path/fstab
158. proc proc proc nodev,noexec,nosuid 0 0
159. sysfs sys sysfs defaults 0 0
160. EOF
162. if [ $? -ne 0 ]; then
163. echo "Failed to add configuration"
164. return 1
165. fi
167. return 0
168. }
170. trim()
171. {
172. rootfs=$1
173. release=$2
175. # provide the lxc service
176. cat <<EOF > $rootfs/etc/init/lxc.conf
177. # fake some events needed for correct startup other services
179. description "Container Upstart"
181. start on startup
183. script
184. rm -rf /var/run/*.pid
185. rm -rf /var/run/network/*
186. /sbin/initctl emit stopped JOB=udevtrigger --no-wait
187. /sbin/initctl emit started JOB=udev --no-wait
188. end script
189. EOF
191. # fix buggus runlevel with sshd
192. cat <<EOF > $rootfs/etc/init/ssh.conf
193. # ssh - OpenBSD Secure Shell server
194. #
195. # The OpenSSH server provides secure shell access to the system.
197. description "OpenSSH server"
199. start on filesystem
200. stop on runlevel [!2345]
202. expect fork
203. respawn
204. respawn limit 10 5
205. umask 022
206. # replaces SSHD_OOM_ADJUST in /etc/default/ssh
207. oom never
209. pre-start script
210. test -x /usr/sbin/sshd || { stop; exit 0; }
211. test -e /etc/ssh/sshd_not_to_be_run && { stop; exit 0; }
212. test -c /dev/null || { stop; exit 0; }
214. mkdir -p -m0755 /var/run/sshd
215. end script
217. # if you used to set SSHD_OPTS in /etc/default/ssh, you can change the
218. # 'exec' line here instead
219. exec /usr/sbin/sshd
220. EOF
222. cat <<EOF > $rootfs/etc/init/console.conf
223. # console - getty
224. #
225. # This service maintains a console on tty1 from the point the system is
226. # started until it is shut down again.
228. start on stopped rc RUNLEVEL=[2345]
229. stop on runlevel [!2345]
231. respawn
232. exec /sbin/getty -8 38400 /dev/console
233. EOF
235. cat <<EOF > $rootfs/lib/init/fstab
236. # /lib/init/fstab: cleared out for bare-bones lxc
237. EOF
239. # reconfigure some services
240. if [ -z "$LANG" ]; then
241. chroot $rootfs locale-gen en_US.UTF-8
242. chroot $rootfs update-locale LANG=en_US.UTF-8
243. else
244. chroot $rootfs locale-gen $LANG
245. chroot $rootfs update-locale LANG=$LANG
246. fi
248. # remove pointless services in a container
249. chroot $rootfs /usr/sbin/update-rc.d -f ondemand remove
251. chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls u*.conf); do mv $f $f.orig; done'
252. chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls tty[2-9].conf); do mv $f $f.orig; done'
253. chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls plymouth*.conf); do mv $f $f.orig; done'
254. chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls hwclock*.conf); do mv $f $f.orig; done'
255. chroot $rootfs /bin/bash -c 'cd /etc/init; for f in $(ls module*.conf); do mv $f $f.orig; done'
257. # if this isn't lucid, then we need to twiddle the network upstart bits :(
258. if [ $release != "lucid" ]; then
259. sed -i 's/^.*emission handled.*$/echo Emitting lo/' $rootfs/etc/network/if-up.d/upstart
260. fi
261. }
263. post_process()
264. {
265. rootfs=$1
266. release=$2
267. trim_container=$3
269. if [ $trim_container -eq 1 ]; then
270. trim $rootfs $release
271. elif [ ! -f $rootfs/etc/init/container-detect.conf ]; then
272. # Make sure we have a working resolv.conf
273. cresolvonf="${rootfs}/etc/resolv.conf"
274. mv $cresolvonf ${cresolvonf}.lxcbak
275. cat /etc/resolv.conf > ${cresolvonf}
277. # for lucid, if not trimming, then add the ubuntu-virt
278. # ppa and install lxcguest
279. if [ $release = "lucid" ]; then
280. chroot $rootfs apt-get install --force-yes -y python-software-properties
281. chroot $rootfs add-apt-repository ppa:ubuntu-virt/ppa
282. fi
284. chroot $rootfs apt-get update
285. chroot $rootfs apt-get install --force-yes -y lxcguest
287. # Restore old resolv.conf
288. rm -f ${cresolvonf}
289. mv ${cresolvonf}.lxcbak ${cresolvonf}
290. fi
292. # If the container isn't running a native architecture, setup multiarch
293. if [ -x "$(ls -1 ${rootfs}/usr/bin/qemu-*-static 2>/dev/null)" ]; then
294. dpkg_version=$(chroot $rootfs dpkg-query -W -f='${Version}' dpkg)
295. if chroot $rootfs dpkg --compare-versions $dpkg_version ge "1.16.2"; then
296. chroot $rootfs dpkg --add-architecture ${hostarch}
297. else
298. mkdir -p ${rootfs}/etc/dpkg/dpkg.cfg.d
299. echo "foreign-architecture ${hostarch}" > ${rootfs}/etc/dpkg/dpkg.cfg.d/lxc-multiarch
300. fi
302. # Save existing value of MIRROR and SECURITY_MIRROR
303. DEFAULT_MIRROR=$MIRROR
304. DEFAULT_SECURITY_MIRROR=$SECURITY_MIRROR
306. # Write a new sources.list containing both native and multiarch entries
307. > ${rootfs}/etc/apt/sources.list
308. write_sourceslist $rootfs $arch "native"
310. MIRROR=$DEFAULT_MIRROR
311. SECURITY_MIRROR=$DEFAULT_SECURITY_MIRROR
312. write_sourceslist $rootfs $hostarch "multiarch"
314. # Finally update the lists and install upstart using the host architecture
315. chroot $rootfs apt-get update
316. chroot $rootfs apt-get install --force-yes -y --no-install-recommends upstart:${hostarch} mountall:${hostarch} iproute:${hostarch} isc-dhcp-client:${hostarch}
317. fi
319. # rmdir /dev/shm for containers that have /run/shm
320. # I'm afraid of doing rm -rf $rootfs/dev/shm, in case it did
321. # get bind mounted to the host's /run/shm. So try to rmdir
322. # it, and in case that fails move it out of the way.
323. if [ -d $rootfs/run/shm ]; then
324. [ -d "$rootfs/dev/shm" ] && rmdir $rootfs/dev/shm
325. [ -e "$rootfs/dev/shm" ] && mv $rootfs/dev/shm $rootfs/dev/shm.bak
326. ln -s /run/shm $rootfs/dev/shm
327. fi
328. }
330. do_bindhome()
331. {
332. rootfs=$1
333. user=$2
335. # copy /etc/passwd, /etc/shadow, and /etc/group entries into container
336. pwd=`getent passwd $user` || { echo "Failed to copy password entry for $user"; false; }
337. echo $pwd >> $rootfs/etc/passwd
339. # make sure user's shell exists in the container
340. shell=`echo $pwd | cut -d: -f 7`
341. if [ ! -x $rootfs/$shell ]; then
342. echo "shell $shell for user $user was not found in the container."
343. pkg=`dpkg -S $(readlink -m $shell) | cut -d ':' -f1`
344. echo "Installing $pkg"
345. chroot $rootfs apt-get --force-yes -y install $pkg
346. fi
348. shad=`getent shadow $user`
349. echo "$shad" >> $rootfs/etc/shadow
351. # bind-mount the user's path into the container's /home
352. h=`getent passwd $user | cut -d: -f 6`
353. mkdir -p $rootfs/$h
355. # use relative path in container
356. h2=${h#/}
357. while [ ${h2:0:1} = "/" ]; do
358. h2=${h2#/}
359. done
360. echo "$h $h2 none bind 0 0" >> $path/fstab
362. # Make sure the group exists in container
363. grp=`echo $pwd | cut -d: -f 4` # group number for $user
364. grpe=`getent group $grp` || return 0 # if host doesn't define grp, ignore in container
365. chroot $rootfs getent group "$grpe" || echo "$grpe" >> $rootfs/etc/group
366. }
368. usage()
369. {
370. cat <<EOF
371. $1 -h|--help [-a|--arch] [-b|--bindhome <user>] [--trim] [-d|--debug]
372. [-F | --flush-cache] [-r|--release <release>] [ -S | --auth-key <keyfile>]
373. release: the ubuntu release (e.g. precise): defaults to host release on ubuntu, otherwise uses latest LTS
374. trim: make a minimal (faster, but not upgrade-safe) container
375. bindhome: bind <user>'s home into the container
376. The ubuntu user will not be created, and <user> will have
377. sudo access.
378. arch: the container architecture (e.g. amd64): defaults to host arch
379. auth-key: SSH Public key file to inject into container
380. EOF
381. return 0
382. }
384. options=$(getopt -o a:b:hp:r:xn:FS:d -l arch:,bindhome:,help,path:,release:,trim,name:,flush-cache,auth-key:,debug -- "$@")
385. if [ $? -ne 0 ]; then
386. usage $(basename $0)
387. exit 1
388. fi
389. eval set -- "$options"
391. release=precise # Default to the last Ubuntu LTS release for non-Ubuntu systems
392. if [ -f /etc/lsb-release ]; then
393. . /etc/lsb-release
394. if [ "$DISTRIB_ID" = "Ubuntu" ]; then
395. release=$DISTRIB_CODENAME
396. fi
397. fi
399. bindhome=
400. arch=$(arch)
402. # Code taken from debootstrap
403. if [ -x /usr/bin/dpkg ] && /usr/bin/dpkg --print-architecture >/dev/null 2>&1; then
404. arch=`/usr/bin/dpkg --print-architecture`
405. elif type udpkg >/dev/null 2>&1 && udpkg --print-architecture >/dev/null 2>&1; then
406. arch=`/usr/bin/udpkg --print-architecture`
407. else
408. arch=$(arch)
409. if [ "$arch" = "i686" ]; then
410. arch="i386"
411. elif [ "$arch" = "x86_64" ]; then
412. arch="amd64"
413. elif [ "$arch" = "armv7l" ]; then
414. arch="armel"
415. fi
416. fi
418. debug=0
419. trim_container=0
420. hostarch=$arch
421. flushcache=0
422. while true
423. do
424. case "$1" in
425. -h|--help) usage $0 && exit 0;;
426. -p|--path) path=$2; shift 2;;
427. -n|--name) name=$2; shift 2;;
428. -F|--flush-cache) flushcache=1; shift 1;;
429. -r|--release) release=$2; shift 2;;
430. -b|--bindhome) bindhome=$2; shift 2;;
431. -a|--arch) arch=$2; shift 2;;
432. -x|--trim) trim_container=1; shift 1;;
433. -S|--auth-key) auth_key=$2; shift 2;;
434. -d|--debug) debug=1; shift 1;;
435. --) shift 1; break ;;
436. *) break ;;
437. esac
438. done
440. if [ $debug -eq 1 ]; then
441. set -x
442. fi
444. if [ -n "$bindhome" ]; then
445. pwd=`getent passwd $bindhome`
446. if [ $? -ne 0 ]; then
447. echo "Error: no password entry found for $bindhome"
448. exit 1
449. fi
450. fi
453. if [ "$arch" == "i686" ]; then
454. arch=i386
455. fi
457. if [ $hostarch = "i386" -a $arch = "amd64" ]; then
458. echo "can't create amd64 container on i386"
459. exit 1
460. fi
462. type debootstrap
463. if [ $? -ne 0 ]; then
464. echo "'debootstrap' command is missing"
465. exit 1
466. fi
468. if [ -z "$path" ]; then
469. echo "'path' parameter is required"
470. exit 1
471. fi
473. if [ "$(id -u)" != "0" ]; then
474. echo "This script should be run as 'root'"
475. exit 1
476. fi
478. rootfs=$path/rootfs
479. ##執行的第一個操作，rootfs文件系統掛載點，flushcache創建cache的目錄，release創建實例的版本
480. install_ubuntu $rootfs $release $flushcache
481. if [ $? -ne 0 ]; then
482. echo "failed to install ubuntu $release"
483. exit 1
484. fi
486. configure_ubuntu $rootfs $name $release ##將鏡像從cache拷貝到真正的rootfs
487. if [ $? -ne 0 ]; then
488. echo "failed to configure ubuntu $release for a container"
489. exit 1
490. fi
492. copy_configuration $path $rootfs $name $arch $release ##在根目錄下生成config文件，並在fstab中掛載/proc和/fs
493. if [ $? -ne 0 ]; then
494. echo "failed write configuration file"
495. exit 1
496. fi

##配置resolv.conf,並在新生成的鏡像中安裝一些必要的軟件，如：lxcguest

1. post_process $rootfs $release $trim_container
3. if [ -n "$bindhome" ]; then
4. do_bindhome $rootfs $bindhome
5. finalize_user $bindhome
6. else
7. finalize_user ubuntu ##創建用戶/屬組，配置ssh用戶名和密碼
8. fi
10. echo ""
11. echo "##"
12. echo "# The default user is 'ubuntu' with password 'ubuntu'!"
13. echo "# Use the 'sudo' command to run tasks as root in the container."
14. echo "##"
15. echo ""

lxc創建ubuntu虛擬機的詳細過程參見上面紅色注釋！
LXC的其他內容將會在後面的文章中繼續介紹！ http://www.linuxidc.com/Linux/2012-07/66523.htm