OpenStack服务开机自启动

1 浅析 Linux 初始化 init 系统

第1部分sysvinit: https://www.ibm.com/developerworks/cn/linux/1407_liuming_init1/
第2部分UpStart: https://www.ibm.com/developerworks/cn/linux/1407_liuming_init2/
第3部分Systemd: https://www.ibm.com/developerworks/cn/linux/1407_liuming_init3/

1.1 SysVInit

1.2 UpStart

1.3 Systemd

1.3.1 基本

1 System单元的概念
系统初始化需要做的事情非常多。需要启动后台服务，比如启动 SSHD 服务；需要做配置工作，比如挂载文件系统。这个过程中的每一步都被 systemd 抽象为一个配置单元，即 unit。
单元的常见类型:
service unit : 文件扩展名为.service，用于定义系统类服务
target unit : 文件扩展为.target,用于实现模拟”运行级别”
device unit : 文件扩展为.device,用于定义内核识别的设备。
mount unit : 文件扩展为.mount,定义文件系统挂载点，利用logind服务，为用户的会话进程分配CGroup资源
socket unit : 文件扩展为.socket,用于标识进程间通信的socket文件
snapshot unit : 文件扩展为.snapshot,管理系统快照
swap unit : 文件扩展为.swap,用于标识swap设备
automount unit : 文件扩展为.automount,文件系统自动挂载设备
path unit : 文件扩展为.path，用于定义文件系统中的一个文件或目录
timer unit : 文件扩展为.timer,定时器配置单元，用来定时触发用户定义的操作，这类配置单元取代了atd、crond等传统的定时服务

1.3.2 初始化过程

1. 当你打开电源后电脑所做的第一件事情就是BIOS初始化。BIOS会读取引导设备设定，定位并传递系统控制权给MBR（假设硬盘是第一引导设备）。
2. MBR从Grub或LILO引导程序读取相关信息并初始化内核。接下来将由Grub或LILO继续引导系统。如果你在grub配置文件里指定了systemd作为引导管理程序，之后的引导过程将由systemd完成。Systemd使用“target”来处理引导和服务管理过程。这些systemd里的“target”文件被用于分组不同的引导单元以及启动同步进程。

root@compute:~# grep -R systemd /etc/grub.d/* 
/etc/grub.d/10_linux:SUPPORTED_INITS="sysvinit:/lib/sysvinit/init systemd:/lib/systemd/systemd upstart:/sbin/upstart"
/etc/grub.d/20_linux_xen:SUPPORTED_INITS="sysvinit:/lib/sysvinit/init systemd:/lib/systemd/systemd upstart:/sbin/upstart"

3. systemd执行的第一个目标是graphical.target。

root@compute:~# systemctl get-default
graphical.target

查看运行级别：

root@compute:~# runlevel
N 5

文件graphical.target的实际位置是/lib/systemd/system/graphical.target。

root@compute:~# find / -name "graphical.target"
/lib/systemd/system/graphical.target

graphical.target文件的内容:

root@compute:~# cat /lib/systemd/system/graphical.target
#  This file is part of systemd.
#
#  systemd 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.

[Unit]
Description=Graphical Interface
Documentation=man:systemd.special(7)
Requires=multi-user.target
Wants=display-manager.service
Conflicts=rescue.service rescue.target
After=multi-user.target rescue.service rescue.target display-manager.service
AllowIsolate=yes

4. 在这个阶段，会启动multi-user.target，而这个target将自己的子单元放在目录“/etc/systemd/system/multi-user.target.wants”里。这个target为多用户支持设定系统环境。非root用户会在这个阶段的引导过程中启用。防火墙相关的服务也会在这个阶段启动。

root@compute:~# cat /lib/systemd/system/multi-user.target
[Unit]
Description=Multi-User System
Documentation=man:systemd.special(7)
Requires=basic.target
Conflicts=rescue.service rescue.target
After=basic.target rescue.service rescue.target
AllowIsolate=yes

"multi-user.target"会将控制权交给另一层“basic.target”。

目录“/etc/systemd/system/multi-user.target.wants”：

root@compute:~# ls /etc/systemd/system/multi-user.target.wants/
atd.service        cron.service            lxcfs.service           neutron-linuxbridge-agent.service    openstack.service      rsyslog.service           snapd.service
cgmanager.service  libvirt-bin.service     lxd-containers.service  neutron-linuxbridge-cleanup.service  open-vm-tools.service  snapd.autoimport.service  ssh.service
cgproxy.service    libvirt-guests.service  networking.service      nova-compute.service                 remote-fs.target       snapd.refresh.timer       ufw.service

5. "basic.target"单元用于启动普通服务特别是图形管理服务。它通过/etc/systemd/system/basic.target.wants目录来决定哪些服务会被启动，basic.target之后将控制权交给sysinit.target.

root@compute:~# cat /lib/systemd/system/basic.target 
[Unit]
Description=Basic System
Documentation=man:systemd.special(7)
Requires=sysinit.target
Wants=sockets.target timers.target paths.target slices.target
After=sysinit.target sockets.target paths.target slices.target tmp.mount

Wants=tmp.mount

6. "sysinit.target"会启动重要的系统服务例如系统挂载，内存交换空间和设备，内核补充选项等等。

root@compute:~# cat /lib/systemd/system/sysinit.target
[Unit]
Description=System Initialization
Documentation=man:systemd.special(7)
Conflicts=emergency.service emergency.target
Wants=local-fs.target swap.target
After=local-fs.target swap.target emergency.service emergency.target

sysinit.target在启动过程中会传递给local-fs.target。

7. local-fs.target，这个target单元不会启动用户相关的服务，它只处理底层核心服务。这个target会根据/etc/fstab和/etc/inittab来执行相关操作。

root@compute:~# cat /lib/systemd/system/local-fs.target
[Unit]
Description=Local File Systems
Documentation=man:systemd.special(7)
DefaultDependencies=no
Conflicts=shutdown.target
After=local-fs-pre.target
OnFailure=emergency.target
OnFailureJobMode=replace-irreversibly

参考资料：

1 http://www.ruanyifeng.com/blog/2016/03/systemd-tutorial-commands.html

2 http://www.ruanyifeng.com/blog/2016/03/systemd-tutorial-part-two.html

3 最简明扼要的 Systemd 教程，只需十分钟： https://linux.cn/article-6888-1.html

4 走进Linux之systemd启动过程：https://linux.cn/article-5457-1.html

1.4 systemd & sysvinit

主要差别如下：

（1）默认的 RunLevel（在/etc/inittab文件设置）现在被默认的 Target 取代，位置是/etc/systemd/system/default.target，通常符号链接到graphical.target（图形界面）或者multi-user.target（多用户命令行）。
（2）启动脚本的位置，以前是/etc/init.d目录，符号链接到不同的 RunLevel 目录 （比如/etc/rc3.d、/etc/rc5.d等），现在则存放在/lib/systemd/system和/etc/systemd/system目录。
（3）配置文件的位置，以前init进程的配置文件是/etc/inittab，各种服务的配置文件存放在/etc/sysconfig目录。现在的配置文件主要存放在/lib/systemd目录，在/etc/systemd目录里面的修改可以覆盖原始设置。

2 命令启动Openstck服务

2.1 servcie命令

service  runs   a  System V init script or upstart job in as predictable an environment as possible, removing most environment variables and with the current working directory set to /.

使用如下形式手动重启、关闭或启动:

service SCRIPT COMMAND [OPTIONS]
The SCRIPT parameter specifies a System V init script, located in /etc/init.d/SCRIPT, or the name of an upstart job in /etc/init. 
The existence of an upstart job of the  same  name  as  a  script  in  /etc/init.d will cause the upstart job to take precedence over the init.d script.  
The supported values of COMMAND depend on the invoked script.  service passes COMMAND and OPTIONS to the init script unmodified. 
For upstart jobs, start, stop, status, are passed through to their upstart equivalents. 
Restart will call the upstart 'stop' for the job, followed immediately by the 'start', and will exit with the return code of the start command.  
All scripts should support at least the start and stop commands.  

如：

# service nova-api restart

System V init scripts和upstart jobs目录结构

/etc/init
    The directory containing upstart jobs.

/etc/init.d
    The directory containing System V init scripts.

/etc/rc?.d/
    The directories containing the links used by init and managed by update-rc.d.

/etc/init.d/skeleton
    Model for use by writers of init.d scripts.

/var/lib/sysv-rc/legacy-bootsequence
    Flag indicating the machine is using legacy mode for boot script ordering.

2.2 systemctl

systemctl:

  start NAME...                   Start (activate) one or more units
  stop NAME...                    Stop (deactivate) one or more units
  reload NAME...                  Reload one or more units
  restart NAME...                 Start or restart one or more units

root@compute:~# ps -ef | grep nova
nova      3489     1  0 May19 ?        00:03:01 /usr/bin/python /usr/bin/nova-compute --config-file=/etc/nova/nova.conf --config-file=/etc/nova/nova-compute.conf --log-file=/var/log/nova/nova-compute.log
root@compute:~# systemctl stop nova-compute
root@compute:~# ps -ef | grep nova
root      9624  1821  0 09:19 pts/0    00:00:00 grep --color=auto nova
root@compute:~# systemctl start nova-compute
root@compute:~# ps -ef | grep nova
nova      9644     1 99 09:19 ?        00:00:02 /usr/bin/python /usr/bin/nova-compute --config-file=/etc/nova/nova.conf --config-file=/etc/nova/nova-compute.conf --log-file=/var/log/nova/nova-compute.log

3 开机自启动

OpenStack中的各个组件服务都会以守护进程形式在系统后台运行，并且是开机自启动。

3.1 sysvinit

以nova-api为例，脚本文件/etc/init.d/nova-api，

root@controller:~# ls /etc/init.d/nova-api 
/etc/init.d/nova-api
root@controller:~# cat /etc/init.d/nova-api 
#!/bin/sh
### BEGIN INIT INFO
# Provides:          nova-api
# Required-Start:    $network $local_fs $remote_fs $syslog
# Required-Stop:     $remote_fs
# Should-Start:      postgresql mysql keystone rabbitmq-server ntp
# Should-Stop:       postgresql mysql keystone rabbitmq-server ntp
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Nova API server
# Description:       Frontend Nova API server
### END INIT INFO

# Author: Julien Danjou <[e-mail]>

# PATH should only include /usr/* if it runs after the mountnfs.sh script
PATH=/sbin:/usr/sbin:/bin:/usr/bin
DESC="OpenStack Compute API"
PROJECT_NAME=nova
NAME=${PROJECT_NAME}-api
#!/bin/sh
# The content after this line comes from openstack-pkg-tools
# and has been automatically added to a .init.in script, which
# contains only the descriptive part for the daemon. Everything
# else is standardized as a single unique script.

# Author: Thomas Goirand <[e-mail]>

# PATH should only include /usr/* if it runs after the mountnfs.sh script
PATH=/sbin:/usr/sbin:/bin:/usr/bin

if [ -z "${DAEMON}" ] ; then
	DAEMON=/usr/bin/${NAME}
fi
PIDFILE=/var/run/${PROJECT_NAME}/${NAME}.pid
if [ -z "${SCRIPTNAME}" ] ; then
	SCRIPTNAME=/etc/init.d/${NAME}
fi
if [ -z "${SYSTEM_USER}" ] ; then
	SYSTEM_USER=${PROJECT_NAME}
fi
if [ -z "${SYSTEM_USER}" ] ; then
	SYSTEM_GROUP=${PROJECT_NAME}
fi
if [ "${SYSTEM_USER}" != "root" ] ; then
	STARTDAEMON_CHUID="--chuid ${SYSTEM_USER}:${SYSTEM_GROUP}"
fi
if [ -z "${CONFIG_FILE}" ] ; then
	CONFIG_FILE=/etc/${PROJECT_NAME}/${PROJECT_NAME}.conf
fi
LOGFILE=/var/log/${PROJECT_NAME}/${NAME}.log
if [ -z "${NO_OPENSTACK_CONFIG_FILE_DAEMON_ARG}" ] ; then
	DAEMON_ARGS="${DAEMON_ARGS} --config-file=${CONFIG_FILE}"
fi

# Exit if the package is not installed
[ -x $DAEMON ] || exit 0

# If ran as root, create /var/lock/X, /var/run/X, /var/lib/X and /var/log/X as needed
if [ `whoami` = "root" ] ; then
	for i in lock run log lib ; do
		mkdir -p /var/$i/${PROJECT_NAME}
		chown ${SYSTEM_USER} /var/$i/${PROJECT_NAME}
	done
fi

# This defines init_is_upstart which we use later on (+ more...)
. /lib/lsb/init-functions

# Manage log options: logfile and/or syslog, depending on user's choosing
[ -r /etc/default/openstack ] && . /etc/default/openstack
[ -r /etc/default/$NAME ] && . /etc/default/$NAME
[ "x$USE_SYSLOG" = "xyes" ] && DAEMON_ARGS="$DAEMON_ARGS --use-syslog"
[ "x$USE_LOGFILE" != "xno" ] && DAEMON_ARGS="$DAEMON_ARGS --log-file=$LOGFILE"

do_start() {
	start-stop-daemon --start --quiet --background ${STARTDAEMON_CHUID} --make-pidfile --pidfile ${PIDFILE} --chdir /var/lib/${PROJECT_NAME} --startas $DAEMON \
			--test > /dev/null || return 1
	start-stop-daemon --start --quiet --background ${STARTDAEMON_CHUID} --make-pidfile --pidfile ${PIDFILE} --chdir /var/lib/${PROJECT_NAME} --startas $DAEMON \
			-- $DAEMON_ARGS || return 2
}

do_stop() {
	start-stop-daemon --stop --quiet --retry=TERM/30/KILL/5 --pidfile $PIDFILE
	RETVAL=$?
	rm -f $PIDFILE
	return "$RETVAL"
}

do_systemd_start() {
	exec $DAEMON $DAEMON_ARGS
}

case "$1" in
start)
	init_is_upstart > /dev/null 2>&1 && exit 1
	log_daemon_msg "Starting $DESC" "$NAME"
	do_start
	case $? in
		0|1) log_end_msg 0 ;;
		2) log_end_msg 1 ;;
	esac
;;
stop)
	init_is_upstart > /dev/null 2>&1 && exit 0
	log_daemon_msg "Stopping $DESC" "$NAME"
	do_stop
	case $? in
		0|1) log_end_msg 0 ;;
		2) log_end_msg 1 ;;
	esac
;;
status)
	status_of_proc "$DAEMON" "$NAME" && exit 0 || exit $?
;;
systemd-start)
	do_systemd_start
;;  
restart|force-reload)
	init_is_upstart > /dev/null 2>&1 && exit 1
	log_daemon_msg "Restarting $DESC" "$NAME"
	do_stop
	case $? in
	0|1)
		do_start
		case $? in
			0) log_end_msg 0 ;;
			1) log_end_msg 1 ;; # Old process is still running
			*) log_end_msg 1 ;; # Failed to start
		esac
	;;
	*) log_end_msg 1 ;; # Failed to stop
	esac
;;
*)
	echo "Usage: $SCRIPTNAME {start|stop|status|restart|force-reload|systemd-start}" >&2
	exit 3
;;
esac

exit 0

3.2 upstart

Upstartinit是基于事件驱动的服务启动机制，可以使多个系统任务在保持依赖关系的前提下并发启动。

通过/etc/init下的一系列 *.conf 配置文件来指定各种系统服务的依赖关系（启动时机）。系统启动时，upstart主进程/sbin/init会解析这些配置文件，按照指定的依赖关系并发启动各种服务与应用。
将自己的程序加入到系统的服务启动机制中，可以让其开机自启动。只需要在/etc/init下增加xxx.conf配置文件即可，xxx是service的服务名字。

两个概念：
1. init: upstart主进程，是Linux系统中的“应用程序管理器”，是其他所有进程的源头（PID为1），它会读取配置文件，处理各种服务和应用程序的依赖关系，根据事件（信号）来启动这些功能与服务，并动态地进行管理。
2.initctl:upstart事件管理器，可以被应用程序进程用来通知init哪些事件（信号）发生。

nova-api的配置/etc/init/nova-api.conf：

root@controller:~# ls /etc/init/nova-api.conf 
/etc/init/nova-api.conf
root@controller:~# 
root@controller:~# cat /etc/init/nova-api.conf 
description "OpenStack Compute API"
author "Thomas Goirand <[e-mail]>"

start on runlevel [2345]
stop on runlevel [!2345]

chdir /var/run

respawn
respawn limit 20 5
limit nofile 65535 65535

pre-start script
	for i in lock run log lib ; do
		mkdir -p /var/$i/nova
		chown nova /var/$i/nova
	done
end script

script
	[ -x "/usr/bin/nova-api" ] || exit 0
	DAEMON_ARGS=""
	[ -r /etc/default/openstack ] && . /etc/default/openstack
	[ -r /etc/default/$UPSTART_JOB ] && . /etc/default/$UPSTART_JOB
	[ "x$USE_SYSLOG" = "xyes" ] && DAEMON_ARGS="$DAEMON_ARGS --use-syslog"
	[ "x$USE_LOGFILE" != "xno" ] && DAEMON_ARGS="$DAEMON_ARGS --log-file=/var/log/nova/nova-api.log"

	exec start-stop-daemon --start --chdir /var/lib/nova \
		--chuid nova:nova --make-pidfile --pidfile /var/run/nova/nova-api.pid \
		--exec /usr/bin/nova-api -- --config-file=/etc/nova/nova.conf ${DAEMON_ARGS}
end script

upstart init启动服务在init进程起来后会读取/etc/init/中的服务程序配置文件。/etc/init.d下的执行脚本名字与/etc/init下的配置名字对应。/etc/init/neutron-server.conf与/etc/init.d/neutron-server对应。如果/etc/init.d/neutron-server被删除，也不会影响service neutron-server start的启动。服务启动的某些配置完全可以在/etc/init/xxx.conf中增加。

实验：Ubuntu14.04中，当把/etc/init/nova-compute.conf文件移除后，重启后，nova-compute服务不能启动

实验：Ubuntu14.04中，当把/etc/init.d/nova-compute文件移除后，重启后，nova-compute服务正常启动

3.3 systemd

1 ubuntu16.04系统中openstack服务自启动配置存放在 /etc/systemd/system/multi-user.target.wants/，查看

root@compute:~# ls /etc/systemd/system/multi-user.target.wants/
neutron-linuxbridge-agent.service    openstack.service      rsyslog.service           snapd.service
neutron-linuxbridge-cleanup.service  open-vm-tools.service  snapd.autoimport.service  ssh.service
nova-compute.service                 remote-fs.target       snapd.refresh.timer       ufw.service

2 查看nova-compute.service内容：

root@compute:~# cat /etc/systemd/system/multi-user.target.wants/nova-compute.service 
[Unit]
Description=OpenStack Compute
After=libvirt-bin.service postgresql.service mysql.service keystone.service rabbitmq-server.service ntp.service neutron-ovs-cleanup.service 

[Service]
User=nova
Group=nova
Type=simple
WorkingDirectory=/var/lib/nova
PermissionsStartOnly=true
ExecStartPre=/bin/mkdir -p /var/lock/nova /var/log/nova /var/lib/nova
ExecStartPre=/bin/chown nova:nova /var/lock/nova /var/lib/nova
ExecStartPre=/bin/chown nova:adm /var/log/nova
ExecStart=/etc/init.d/nova-compute systemd-start
Restart=on-failure
LimitNOFILE=65535
TimeoutStopSec=15

[Install]
WantedBy=multi-user.target

nova-compute.service被调用后，会执行etc/init.d/nova-compute脚本

3 查看nova-compute的自启动脚本和配置都存在：

root@compute:~# ls /etc/init/nova-compute.conf 
/etc/init/nova-compute.conf
root@compute:~# ls /etc/init.d/nova-compute 
/etc/init.d/nova-compute

因为没有使用upstart，所以/etc/init/nova-compute.conf配置是不起作用的。

实验：Ubuntu16.04中，当把/etc/init/nova-compute.conf文件移除后，重启后，nova-compute服务正常启动

实验：Ubuntu16.04中，当把/etc/init.d/nova-compute文件移除后，重启后，nova-compute服务不能启动

4 取消开机自启动

4.1 sysvinit

4.2 upstart

nova-api.conf为例， 只需要把start on注释掉就好了。不要删除conf文件，这样以后仍然可以用start/stop这些命令来控制它的状态。

4.3 systemd

方法1：移除文件etc/init.d/nova-compute

方法2：修改文件/etc/systemd/system/multi-user.target.wants/nova-compute.service

5 nova-api调用执行

(1) /etc/init/nova-api.conf关键代码如下：

exec start-stop-daemon --start --chdir /var/lib/nova \
		--chuid nova:nova --make-pidfile --pidfile /var/run/nova/nova-api.pid \
		--exec /usr/bin/nova-api -- --config-file=/etc/nova/nova.conf ${DAEMON_ARGS}

其实就是 用start-stop-daemon去调用/usr/bin/nova-api

(2) 查看/usr/bin/nova-api

root@controller:~# cat /usr/bin/nova-api 
#!/usr/bin/python
# PBR Generated from u'console_scripts'

import sys

from nova.cmd.api import main

if __name__ == "__main__":
    sys.exit(main())

其中 调用了nova/cmd目录下的api.py文件中的main函数
(3) 查看api.py文件

root@controller:~# python
Python 2.7.6 (default, Oct 26 2016, 20:30:19) 
[GCC 4.8.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import nova
>>> print nova.__path__
['/usr/lib/python2.7/dist-packages/nova']

到目录/usr/lib/python2.7/dist-packages/nova/cmd下：

root@controller:/usr/lib/python2.7/dist-packages/nova/cmd# ll api*py
-rw-r--r-- 1 root root 1514 Nov 22 11:11 api_ec2.py
-rw-r--r-- 1 root root 1781 Nov 22 11:11 api_metadata.py
-rw-r--r-- 1 root root 1481 Nov 22 11:11 api_os_compute.py
-rw-r--r-- 1 root root 1846 Nov 22 11:11 api.py