我使用过的Linux命令之service - 系统服务管理
我使用过的Linux命令之service - 系统服务管理

本文链接：http://codingstandards.iteye.com/blog/985455 ? （转载请注明出处）

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用途说明

service命令用于对系统服务进行管理，比如启动（start）、停止（stop）、重启（restart）、查看状态（status）等。相关的命令还包括chkconfig、ntsysv等，chkconfig用于查看、设置服务的运行级别，ntsysv用于直观方便的设置各个服务是否自动启动。service命令本身是一个shell脚本，它在/etc/init.d/目录查找指定的服务脚本，然后调用该服务脚本来完成任务。

看看下面的手册页可能更加清楚的了解service的内幕：service运行指定服务（称之为System V初始脚本）时，把大部分环境变量去掉了，只保留LANG和TERM两个环境变量，并且把当前路径置为/，也就是说是在一个可以预测的非常干净的环境中运行服务脚本。这种脚本保存在/etc/init.d目录中，它至少要支持start和stop命令。

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?? exit 1
fi

cd /
while [ $# -gt 0 ]; do
? case "${1}" in
??? --help | -h | --h* )
?????? echo "${USAGE}" >&2
?????? exit 0
?????? ;;
??? --version | -V )
?????? echo "${VERSION}" >&2
?????? exit 0
?????? ;;
??? *)
?????? if [ -z "${SERVICE}" -a $# -eq 1 -a "${1}" = "--status-all" ]; then
????????? cd ${SERVICEDIR}
????????? for SERVICE in * ; do
??????????? case "${SERVICE}" in
????????????? functions | halt | killall | single| linuxconf| kudzu)
????????????????? ;;
????????????? *)
??????????????? if ! is_ignored_file "${SERVICE}" \
??????????????????? && [ -x "${SERVICEDIR}/${SERVICE}" ]; then
????????????????? env -i LANG="$LANG" PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" status
??????????????? fi
??????????????? ;;
??????????? esac
????????? done
????????? exit 0
?????? elif [ $# -eq 2 -a "${2}" = "--full-restart" ]; then
????????? SERVICE="${1}"
????????? if [ -x "${SERVICEDIR}/${SERVICE}" ]; then
??????????? env -i LANG="$LANG" PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" stop
??????????? env -i LANG="$LANG" PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" start
??????????? exit $?
????????? fi
?????? elif [ -z "${SERVICE}" ]; then
???????? SERVICE="${1}"
?????? else
???????? OPTIONS="${OPTIONS} ${1}"
?????? fi
?????? shift
?????? ;;
?? esac
done

if [ -x "${SERVICEDIR}/${SERVICE}" ]; then
?? env -i LANG="$LANG" PATH="$PATH" TERM="$TERM" "${SERVICEDIR}/${SERVICE}" ${OPTIONS}
else
?? echo $"${SERVICE}: unrecognized service" >&2
?? exit 1
fi
[root@web ~]#

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示例四 crond服务的源码

[root@web init.d]# cat /etc/init.d/crond
#! /bin/bash
#
# crond????????? Start/Stop the cron clock daemon.
#
# chkconfig: 2345 90 60
# description: cron is a standard UNIX program that runs user-specified \
#????????????? programs at periodic scheduled times. vixie cron adds a \
#????????????? number of features to the basic UNIX cron, including better \
#????????????? security and more powerful configuration options.
# processname: crond
# config: /etc/crontab
# pidfile: /var/run/crond.pid

# Source function library.
. /etc/init.d/functions
. /etc/sysconfig/crond
t=${CRON_VALIDATE_MAILRCPTS:-UNSET}
[ "$t" != "UNSET" ] && export CRON_VALIDATE_MAILRCPTS="$t"
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# See how we were called.
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prog="crond"

start() {
??????? echo -n $"Starting $prog: "
??????? if [ -e /var/lock/subsys/crond ]; then
??????????? if [ -e /var/run/crond.pid ] && [ -e /proc/`cat /var/run/crond.pid` ]; then
??????????????? echo -n $"cannot start crond: crond is already running.";
??????????????? failure $"cannot start crond: crond already running.";
??????????????? echo
??????????????? return 1
??????????? fi
??????? fi
??????? daemon crond $CRONDARGS
??????? RETVAL=$?
??????? echo
??????? [ $RETVAL -eq 0 ] && touch /var/lock/subsys/crond;
??????? return $RETVAL
}

stop() {
??????? echo -n $"Stopping $prog: "
??????? if [ ! -e /var/lock/subsys/crond ]; then
??????????? echo -n $"cannot stop crond: crond is not running."
??????????? failure $"cannot stop crond: crond is not running."
??????????? echo
??????????? return 1;
??????? fi
??????? killproc crond
??????? RETVAL=$?
??????? echo
??????? [ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/crond;
??????? return $RETVAL
}

rhstatus() {
??????? status crond
}

restart() {
??????? stop
??????? start
}

reload() {
??????? echo -n $"Reloading cron daemon configuration: "
??????? killproc crond -HUP
??????? RETVAL=$?
??????? echo
??????? return $RETVAL
}

case "$1" in
? start)
??????? start
??????? ;;
? stop)
??????? stop
??????? ;;
? restart)
??????? restart
??????? ;;
? reload)
??????? reload
??????? ;;
? status)
??????? rhstatus
??????? ;;
? condrestart)
??????? [ -f /var/lock/subsys/crond ] && restart || :
??????? ;;
? *)
??????? echo $"Usage: $0 {start|stop|status|reload|restart|condrestart}"
??????? exit 1
esac
[root@web init.d]#

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问题思考相关资料

【1】测试人生 linux 中不常用的命令--service
http://www.51testing.com/?uid-66775-action-viewspace-itemid-78574
【2】linux大棚 《service》-“linux命令五分钟系列”之二
http://roclinux.cn/?p=47
【3】yqh860921 Linux Service 服务管理
http://blogold.chinaunix.net/u3/95470/showart_1934759.html
【4】酷勤 Linux system service 注释
http://www.kuqin.com/linux/20090824/67321.html
【5】momodog 自定义Linux Service
http://momodog.iteye.com/blog/286047

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