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分类： 系统运维
2013-11-21 15:49:20
sendmail 启动脚本分析
(整理日期：2008-3-5)
（脚本文件环境：RedHat 4 EL / sendmail-8.13.1-3.RHEL4.5 ）
一、脚本说是
下列这个脚本是在RedHat 4 EL 下通过service 命令来启动和关闭sendmail 的shell 脚本，其存放目录在：/etc/init.d/sendmail 文件。该文件的权限是：-rwxr-xr-x
二、脚本逐行分析
#!/bin/bash
#
# sendmail This shell script takes care of starting and stopping
# sendmail.
#
# chkconfig: 2345 80 30
# description: Sendmail is a Mail Transport Agent, which is the program \
# that moves mail from one machine to another.
# processname: sendmail
# config: /etc/mail/sendmail.cf
# pidfile: /var/run/sendmail.pid
# 以上部分为一些说明
# Source function library.
. /etc/rc.d/init.d/functions
# 包含 /etc/rc.d/init.d/functions 文件，该文件是系统安装后，系统自带的一个包含常见shell函数的文件。一般众多的shell 脚本程序都使用这个文件，这样可以大大减少编程的工作量。该文件的具体内容见附录部分
# Source networking configuration.
[ -f /etc/sysconfig/network ] && . /etc/sysconfig/network
# 检查在/etc/sysconfig 下，是否存在network这个文件，如果存在则包含这个文件。而这个文件里包含了网络部分的设置，如是该机器是否启动网络，网关，及主机名。该文件的内容是：
NETWORKING=yes
HOSTNAME=test.smartpay.com.cn
GATEWAY=192.168.1.1
# Source sendmail configureation.
if [ -f /etc/sysconfig/sendmail ] ; then
. /etc/sysconfig/sendmail
else
DAEMON=no
QUEUE=1h
fi
# 如果/etc/sysconfig/sendmail 文件存在，则包含这个文件，而这个文件里是定义了两个变量。下面是这个文件里的内容。而如果这个文件不存在，则定义两个变量，DAEMON 和 QUEUE。
[ -z "$SMQUEUE" ] && SMQUEUE="$QUEUE"
[ -z "$SMQUEUE" ] && SMQUEUE=1h
#如果变量SMQUEUE为空的，则这个变量的值为$QUEUE变量的值，也就是上面所包含的sendmail配置文件里定义的或者后来定义的。
#同样，下面的一句也是检测SMQUEUE是否为空，如果为空则将这个变量的值设置成1h。之所以两次对这个变量进行判断，是因为防止因为/etc/sysconfig/sendmail 文件存在，而该文件中又没有定义这个变量，也就是保证这个变量一定要有值
# Check that networking is up.
[ "${NETWORKING}" = "no" ] && exit 0
# 检测当前这台机器的网络功能是否已经启动，如果没有，则退出这个脚本的运行。因为连网络都没有启用，则启动sendmail 没有什么意义
而"${NETWORKING}" 就是在/etc/sysconfig/network文件中定义的一个选项
[ -f /usr/sbin/sendmail ] || exit 0
如果/usr/sbin/sendmail这个文件不存在，则退出脚本的继续执行。在实际系统中这个文件是一个连接文件。lrwxrwxrwx 1 root root 21 Feb 18 15:50 /usr/sbin/sendmail -> /etc/alternatives/mta
RETVAL=0
prog="sendmail"
start() {
# 定义start 函数
# Start daemons.
echo -n $"Starting $prog: "
# 在屏幕上显示出 Starting sendmail 字样，这里的 –n 是表示下面的信息也在一行来显示，之所以带这个参数，所以在系统启动时就会出现”Starting sendmail: [ OK ] “的信息出来。要知道这个显示里的 Starting sendmail：和后面的[ OK ]是在不同的时候显示的。
if test -x /usr/bin/make -a -f /etc/mail/Makefile ; then
make all -C /etc/mail -s > /dev/null
# 如果 /usr/bin/make的文件属性为可执行，且在/etc/mail下有 Makefile文件，则编译 /etc/mail下的所有文件。这是将sendmail的配置文件在启动的时候都重新编译一下。
else
for i in virtusertable access domaintable mailertable ; do
if [ -f /etc/mail/$i ] ; then
makemap hash /etc/mail/$i < /etc/mail/$i
fi
done
fi
如果上述条件不成立，则使用循环语句，分别对/etc/mail下的virtusertable、access 、domaintable、mailertable生成相应的db文件。
/usr/bin/newaliases > /dev/null 2>&1
# 执行/usr/bin/newaliases 命令，且将输出的信息屏蔽掉。关于 2>&1说明如下：
在POSIX shell中，命令的结果可以通过%>的形式来定义（其中%表示文件描述符： 0 为标准备输入，1为标准输出stdout、2为标准错误stderr）！系统默认% 值是1，也就是1>，而1>可以 简写为>，也就是默认为>。
例如：有以下两个文件：
aaa.sh 文件内容
#!/bin/sh
cat bbb.sh
cat aaaaa.sh
bbb.sh 文件内容
#!/bin/sh
for i in aaa bbb ccc ; do
echo -n $i;
done
aaaaa.sh 不存在，当直接执行如下命令则有：
./aaa.sh
#!/bin/sh
for i in aaa bbb ccc ; do
echo -n $i;
done
cat: aaaaa.sh: No such file or directory
这时候正常内容和错误信息都显示在屏幕上，当使用下列命令时则有：
./aaa.sh 2>/dev/null
#!/bin/sh
for i in aaa bbb ccc ; do
echo -n $i;
done
注意：这时候不显示错误信息了，这是因为错误信息被输出到标准输入2上之后又 没有被重新定向到了 /dev/null 下了
而使用下列命令时则有：
./aaa.sh >/dev/null
cat: aaaaa.sh: No such file or directory
注意：这时候只输出错误的信息了。这是因为标准的输出被重定向了 /dev/null下了。而标准输出1是系统默认的，可以省略的，以上命令等于如下命令：
./aaa.sh 1>/dev/null
而当使用下列命令时，则什么信息也没有显示出来，./aaa.sh >/dev/null 2>&1
之所以什么显示也没有，是因为标准输出被重定向到了 /dev/null下了，而标准错误输出又被得定向到了标准备输出了，所以什么都没有显示出来了。
daemon /usr/sbin/sendmail $([ "x$DAEMON" = xyes ] && echo -bd) \
$([ -n "$QUEUE" ] && echo -q$QUEUE) $SENDMAIL_OPTARG
RETVAL=$?
# 使用function 脚本文件里的定义的daemon函数来启动sendmail 服务，其中先判断DAEMON变量的值是不是yes，如果是yes 则在命令的后面添加上 –bd选项，同时判断 QUEUE变量是不是为空，如果不为空，则带上这个选项并加上-q这个选项，最后加上ENDMAIL_OPTARG变量指定的选项。
echo
# 提示信息换行
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/sendmail
# 如果启动正常，则在 /var/lock/subsys目录下生成一个 sendmail 空文件,这个文件跟/var/run下的sendmail.pic文件来标识sendmail服务器已经在运行.
if ! test -f /var/run/sm-client.pid ; then
echo -n $"Starting sm-client: "
touch /var/run/sm-client.pid
chown smmsp:smmsp /var/run/sm-client.pid
if [ -x /usr/bin/selinuxenabled ] && /usr/bin/selinuxenabled; then
/sbin/restorecon /var/run/sm-client.pid
fi
daemon --check sm-client /usr/sbin/sendmail -L sm-msp-queue -Ac \
-q $SMQUEUE $SENDMAIL_OPTARG
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/sm-client
fi
return $RETVAL
}
# 上述这段代码与启动sendmail服务的代码类似，可以比照来看。
reload() {
# 定义重启函数
# Stop
echo -n $"reloading $prog: " # 打印出重启服务信息
/usr/bin/newaliases > /dev/null 2>&1
if [ -x /usr/bin/make -a -f /etc/mail/Makefile ]; then
make all -C /etc/mail -s > /dev/null
else
for i in virtusertable access domaintable mailertable ; do
if [ -f /etc/mail/$i ] ; then
makemap hash /etc/mail/$i < /etc/mail/$i
fi
done
fi
daemon /usr/sbin/sendmail $([ "x$DAEMON" = xyes ] && echo -bd) \
$([ -n "$QUEUE" ] && echo -q$QUEUE)
RETVAL=$?
killproc sendmail –HUP
RETVAL=$?
echo
if [ $RETVAL -eq 0 -a -f /var/run/sm-client.pid ]; then
echo -n $"reloading sm-client: "
killproc sm-client -HUP
RETVAL=$?
echo
fi
return $RETVAL
}
# 上述的语句与start函数的类似，可以对比着查看
stop() { # 定义stop 函数
# Stop daemons.
echo -n $"Shutting down $prog: "
killproc sendmail
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/sendmail
if test -f /var/run/sm-client.pid ; then
echo -n $"Shutting down sm-client: "
killproc sm-client
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && rm -f /var/run/sm-client.pid
[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/sm-client
fi
return $RETVAL
}
# 上述语句与start函数中的语句对比看，比较容易懂
# See how we were called.
# 根据输入的第1个参数来确定调用函数；
case "$1" in
start)
start
;;
stop)
stop
;;
reload)
reload
RETVAL=$?
;;
restart)
stop
start
RETVAL=$?
;;
condrestart)
if [ -f /var/lock/subsys/sendmail ]; then
stop
start
RETVAL=$?
fi
;;
status)
status sendmail
RETVAL=$?
;;
*)
echo $"Usage: $0 {start|stop|restart|condrestart|status}"
exit 1
esac
exit $RETVAL
三、function脚本文件内容
# -*-Shell-script-*-
#
# functions This file contains functions to be used by most or all
# shell scripts in the /etc/init.d directory.
#
TEXTDOMAIN=initscripts
# Make sure umask is sane
umask 022
# Set up a default search path.
PATH="/sbin:/usr/sbin:/bin:/usr/bin:/usr/X11R6/bin"
export PATH
# Get a sane screen width
[ -z "${COLUMNS:-}" ] && COLUMNS=80
[ -z "${CONSOLETYPE:-}" ] && CONSOLETYPE="`/sbin/consoletype`"
if [ -f /etc/sysconfig/i18n -a -z "${NOLOCALE:-}" ] ; then
. /etc/sysconfig/i18n
if [ "$CONSOLETYPE" != "pty" ]; then
case "${LANG:-}" in
ja_JP*|ko_KR*|zh_CN*|zh_TW*|bn_*|bd_*|pa_*|hi_*|ta_*|gu_*)
export LC_MESSAGES=en_US
export LANG
;;
*)
export LANG
;;
esac
else
[ -n "$LC_MESSAGES" ] && export LC_MESSAGES
export LANG
fi
fi
# Read in our configuration
if [ -z "${BOOTUP:-}" ]; then
if [ -f /etc/sysconfig/init ]; then
. /etc/sysconfig/init
else
# This all seem confusing? Look in /etc/sysconfig/init,
# or in /usr/doc/initscripts-*/sysconfig.txt
BOOTUP=color
RES_COL=60
MOVE_TO_COL="echo -en \\033[${RES_COL}G"
SETCOLOR_SUCCESS="echo -en \\033[1;32m"
SETCOLOR_FAILURE="echo -en \\033[1;31m"
SETCOLOR_WARNING="echo -en \\033[1;33m"
SETCOLOR_NORMAL="echo -en \\033[0;39m"
LOGLEVEL=1
fi
if [ "$CONSOLETYPE" = "serial" ]; then
BOOTUP=serial
MOVE_TO_COL=
SETCOLOR_SUCCESS=
SETCOLOR_FAILURE=
SETCOLOR_WARNING=
SETCOLOR_NORMAL=
fi
fi
if [ "${BOOTUP:-}" != "verbose" ]; then
INITLOG_ARGS="-q"
else
INITLOG_ARGS=
fi
# Check if $pid (could be plural) are running
checkpid() {
local i
for i in $* ; do
[ -d "/proc/$i" ] && return 0
done
return 1
}
# A function to start a program.
daemon() {
# Test syntax.
local gotbase= force=
local base= user= nice= bg= pid=
nicelevel=0
while [ "$1" != "${1##[-+]}" ]; do
case $1 in
'') echo $"$0: Usage: daemon [+/-nicelevel] {program}"
return 1;;
--check)
base=$2
gotbase="yes"
shift 2
;;
--check=?*)
base=${1#--check=}
gotbase="yes"
shift
;;
--user)
user=$2
shift 2
;;
--user=?*)
user=${1#--user=}
shift
;;
--force)
force="force"
shift
;;
[-+][0-9]*)
nice="nice -n $1"
shift
;;
*) echo $"$0: Usage: daemon [+/-nicelevel] {program}"
return 1;;
esac
done
# Save basename.
[ -z "$gotbase" ] && base=${1##*/}
# See if it's already running. Look *only* at the pid file.
if [ -f /var/run/${base}.pid ]; then
local line p
read line < /var/run/${base}.pid
for p in $line ; do
[ -z "${p//[0-9]/}" -a -d "/proc/$p" ] && pid="$pid $p"
done
fi
[ -n "${pid:-}" -a -z "${force:-}" ] && return
# make sure it doesn't core dump anywhere unless requested
ulimit -S -c ${DAEMON_COREFILE_LIMIT:-0} >/dev/null 2>&1
# if they set NICELEVEL in /etc/sysconfig/foo, honor it
[ -n "$NICELEVEL" ] && nice="nice -n $NICELEVEL"
# Echo daemon
[ "${BOOTUP:-}" = "verbose" -a -z "$LSB" ] && echo -n " $base"
# And start it up.
if [ -z "$user" ]; then
$nice initlog $INITLOG_ARGS -c "$*"
else
$nice initlog $INITLOG_ARGS -c "runuser -s /bin/bash - $user -c \"$*\""
fi
[ "$?" -eq 0 ] && success $"$base startup" || failure $"$base startup"
}
# A function to stop a program.
killproc() {
RC=0
# Test syntax.
if [ "$#" -eq 0 ]; then
echo $"Usage: killproc {program} [signal]"
return 1
fi
notset=0
# check for second arg to be kill level
if [ -n "$2" ]; then
killlevel=$2
else
notset=1
killlevel="-9"
fi
# Save basename.
base=${1##*/}
echo "base value is:"$base
# Find pid.
pid=
if [ -f /var/run/${base}.pid ]; then
local line p
read line < /var/run/${base}.pid
for p in $line ; do
[ -z "${p//[0-9]/}" -a -d "/proc/$p" ] && pid="$pid $p"
done
fi
if [ -z "$pid" ]; then
pid=`pidof -o $$ -o $PPID -o %PPID -x $1 || \
pidof -o $$ -o $PPID -o %PPID -x $base`
fi
# Kill it.
if [ -n "${pid:-}" ] ; then
[ "$BOOTUP" = "verbose" -a -z "$LSB" ] && echo -n "$base "
if [ "$notset" -eq "1" ] ; then
if checkpid $pid 2>&1; then
# TERM first, then KILL if not dead
kill -TERM $pid >/dev/null 2>&1
usleep 100000
if checkpid $pid && sleep 1 &&
checkpid $pid && sleep 3 &&
checkpid $pid ; then
kill -KILL $pid >/dev/null 2>&1
usleep 100000
fi
fi
checkpid $pid
RC=$?
[ "$RC" -eq 0 ] && failure $"$base shutdown" || success $"$base shutdown"
RC=$((! $RC))
# use specified level only
else
if checkpid $pid; then
kill $killlevel $pid >/dev/null 2>&1
RC=$?
[ "$RC" -eq 0 ] && success $"$base $killlevel" || failure $"$base $killlevel"
fi
fi
else
failure $"$base shutdown"
RC=1
fi
# Remove pid file if any.
if [ "$notset" = "1" ]; then
rm -f /var/run/$base.pid
fi
return $RC
}
# A function to find the pid of a program. Looks *only* at the pidfile
pidfileofproc() {
local base=${1##*/}
# Test syntax.
if [ "$#" = 0 ] ; then
echo $"Usage: pidfileofproc {program}"
return 1
fi
# First try "/var/run/*.pid" files
if [ -f /var/run/$base.pid ] ; then
local line p pid=
read line < /var/run/$base.pid
for p in $line ; do
[ -z "${p//[0-9]/}" -a -d /proc/$p ] && pid="$pid $p"
done
if [ -n "$pid" ]; then
echo $pid
return 0
fi
fi
}
# A function to find the pid of a program.
pidofproc() {
base=${1##*/}
# Test syntax.
if [ "$#" = 0 ]; then
echo $"Usage: pidofproc {program}"
return 1
fi
# First try "/var/run/*.pid" files
if [ -f /var/run/$base.pid ]; then
local line p pid=
read line < /var/run/$base.pid
for p in $line ; do
[ -z "${p//[0-9]/}" -a -d /proc/$p ] && pid="$pid $p"
done
if [ -n "$pid" ]; then
echo $pid
return 0
fi
fi
pidof -o $$ -o $PPID -o %PPID -x $1 || \
pidof -o $$ -o $PPID -o %PPID -x $base
}
status() {
local base=${1##*/}
local pid
# Test syntax.
if [ "$#" = 0 ] ; then
echo $"Usage: status {program}"
return 1
fi
# First try "pidof"
pid=`pidof -o $$ -o $PPID -o %PPID -x $1 || \
pidof -o $$ -o $PPID -o %PPID -x ${base}`
if [ -n "$pid" ]; then
echo $"${base} (pid $pid) is running..."
return 0
fi
# Next try "/var/run/*.pid" files
if [ -f /var/run/${base}.pid ] ; then
read pid < /var/run/${base}.pid
if [ -n "$pid" ]; then
echo $"${base} dead but pid file exists"
return 1
fi
fi
# See if /var/lock/subsys/${base} exists
if [ -f /var/lock/subsys/${base} ]; then
echo $"${base} dead but subsys locked"
return 2
fi
echo $"${base} is stopped"
return 3
}
echo_success() {
[ "$BOOTUP" = "color" ] && $MOVE_TO_COL
echo -n "[ "
[ "$BOOTUP" = "color" ] && $SETCOLOR_SUCCESS
echo -n $"OK"
[ "$BOOTUP" = "color" ] && $SETCOLOR_NORMAL
echo -n " ]"
echo -ne "\r"
return 0
}
echo_failure() {
[ "$BOOTUP" = "color" ] && $MOVE_TO_COL
echo -n "["
[ "$BOOTUP" = "color" ] && $SETCOLOR_FAILURE
echo -n $"FAILED"
[ "$BOOTUP" = "color" ] && $SETCOLOR_NORMAL
echo -n "]"
echo -ne "\r"
return 1
}
echo_passed() {
[ "$BOOTUP" = "color" ] && $MOVE_TO_COL
echo -n "["
[ "$BOOTUP" = "color" ] && $SETCOLOR_WARNING
echo -n $"PASSED"
[ "$BOOTUP" = "color" ] && $SETCOLOR_NORMAL
echo -n "]"
echo -ne "\r"
return 1
}
echo_warning() {
[ "$BOOTUP" = "color" ] && $MOVE_TO_COL
echo -n "["
[ "$BOOTUP" = "color" ] && $SETCOLOR_WARNING
echo -n $"WARNING"
[ "$BOOTUP" = "color" ] && $SETCOLOR_NORMAL
echo -n "]"
echo -ne "\r"
return 1
}
# Inform the graphical boot of our current state
update_boot_stage() {
if [ "$GRAPHICAL" = "yes" -a -x /usr/bin/rhgb-client ]; then
/usr/bin/rhgb-client --update="$1"
fi
return 0
}
# Log that something succeeded
success() {
if [ -z "${IN_INITLOG:-}" ]; then
initlog $INITLOG_ARGS -n $0 -s "$1" -e 1
else
# silly hack to avoid EPIPE killing rc.sysinit
trap "" SIGPIPE
echo "$INITLOG_ARGS -n $0 -s \"$1\" -e 1" >&21
trap - SIGPIPE
fi
[ "$BOOTUP" != "verbose" -a -z "$LSB" ] && echo_success
return 0
}
# Log that something failed
failure() {
rc=$?
if [ -z "${IN_INITLOG:-}" ]; then
initlog $INITLOG_ARGS -n $0 -s "$1" -e 2
else
trap "" SIGPIPE
echo "$INITLOG_ARGS -n $0 -s \"$1\" -e 2" >&21
trap - SIGPIPE
fi
[ "$BOOTUP" != "verbose" -a -z "$LSB" ] && echo_failure
[ -x /usr/bin/rhgb-client ] && /usr/bin/rhgb-client --details=yes
return $rc
}
# Log that something passed, but may have had errors. Useful for fsck
passed() {
rc=$?
if [ -z "${IN_INITLOG:-}" ]; then
initlog $INITLOG_ARGS -n $0 -s "$1" -e 1
else
trap "" SIGPIPE
echo "$INITLOG_ARGS -n $0 -s \"$1\" -e 1" >&21
trap - SIGPIPE
fi
[ "$BOOTUP" != "verbose" -a -z "$LSB" ] && echo_passed
return $rc
}
# Log a warning
warning() {
rc=$?
if [ -z "${IN_INITLOG:-}" ]; then
initlog $INITLOG_ARGS -n $0 -s "$1" -e 1
else
trap "" SIGPIPE
echo "$INITLOG_ARGS -n $0 -s \"$1\" -e 1" >&21
trap - SIGPIPE
fi
[ "$BOOTUP" != "verbose" -a -z "$LSB" ] && echo_warning
return $rc
}
# Run some action. Log its output.
action() {
STRING=$1
echo -n "$STRING "
if [ "${RHGB_STARTED}" != "" -a -w /etc/rhgb/temp/rhgb-console ]; then
echo -n "$STRING " > /etc/rhgb/temp/rhgb-console
fi
shift
initlog $INITLOG_ARGS -c "$*" && success $"$STRING" || failure $"$STRING"
rc=$?
echo
if [ "${RHGB_STARTED}" != "" -a -w /etc/rhgb/temp/rhgb-console ]; then
if [ "$rc" = "0" ]; then
echo_success > /etc/rhgb/temp/rhgb-console
else
echo_failure > /etc/rhgb/temp/rhgb-console
[ -x /usr/bin/rhgb-client ] && /usr/bin/rhgb-client --details=yes
fi
echo
fi
return $rc
}
# returns OK if $1 contains $2
strstr() {
[ "${1#*$2*}" = "$1" ] && return 1
return 0
}
# Confirm whether we really want to run this service
confirm() {
[ -x /usr/bin/rhgb-client ] && /usr/bin/rhgb-client --details=yes
while : ; do
echo -n $"Start service $1 (Y)es/(N)o/(C)ontinue? [Y] "
read answer
if strstr $"yY" "$answer" || [ "$answer" = "" ] ; then
return 0
elif strstr $"cC" "$answer" ; then
rm -f /var/run/confirm
[ -x /usr/bin/rhgb-client ] && /usr/bin/rhgb-client --details=no
return 2
elif strstr $"nN" "$answer" ; then
return 1
fi
done
}
