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mysql启动脚本详解
1 #!/bin/sh 2 # Copyright Abandoned 1996 TCX DataKonsult AB & Monty Program KB & Detron HB 3 # This file is public domain and comes with NO WARRANTY of any kind 4 5 # MySQL daemon start/stop script. 6 7 # Usually this is put in /etc/init.d (at least on machines SYSV R4 based 8 # systems) and linked to /etc/rc3.d/S99mysql and /etc/rc0.d/K01mysql. 9 # When this is done the mysql server will be started when the machine is 10 # started and shut down when the systems goes down. 11 12 # Comments to support chkconfig on RedHat Linux 13 # chkconfig: 2345 64 36 14 # description: A very fast and reliable SQL database engine. 15 16 # Comments to support LSB init script conventions 17 ### BEGIN INIT INFO 18 # Provides: mysql 19 # Required-Start: $local_fs $network $remote_fs 20 # Should-Start: ypbind nscd ldap ntpd xntpd 21 # Required-Stop: $local_fs $network $remote_fs 22 # Default-Start: 2 3 4 5 23 # Default-Stop: 0 1 6 24 # Short-Description: start and stop MySQL 25 # Description: MySQL is a very fast and reliable SQL database engine. 26 ### END INIT INFO 27 28 # If you install MySQL on some other places than /usr, then you 29 # have to do one of the following things for this script to work: 30 # 31 # - Run this script from within the MySQL installation directory 32 # - Create a /etc/my.cnf file with the following information: 33 # [mysqld] 34 # basedir=<path-to-mysql-installation-directory> 35 # - Add the above to any other configuration file (for example ~/.my.ini) 36 # and copy my_print_defaults to /usr/bin 37 # - Add the path to the mysql-installation-directory to the basedir variable 38 # below. 39 # 40 # If you want to affect other MySQL variables, you should make your changes 41 # in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files. 42 43 # If you change base dir, you must also change datadir. These may get 44 # overwritten by settings in the MySQL configuration files. 45 46 basedir= #mysql的安装目录 47 datadir= #数据存储路径 48 49 # Default value, in seconds, afterwhich the script should timeout waiting 50 # for server start. 51 # Value here is overriden by value in my.cnf. 52 # 0 means don‘t wait at all 53 # Negative numbers mean to wait indefinitely 54 service_startup_timeout=900 55 56 # Lock directory for RedHat / SuSE. 57 lockdir=‘/var/lock/subsys‘ #mysql进程锁 58 lock_file_path="$lockdir/mysql" 59 60 # The following variables are only set for letting mysql.server find things. 61 62 # Set some defaults 63 mysqld_pid_file_path= 64 if test -z "$basedir" #依次确定$basedir,$datadir,$bindir等路径 65 then 66 basedir=/usr 67 bindir=/usr/bin 68 if test -z "$datadir" 69 then 70 datadir=/var/lib/mysql 71 fi 72 sbindir=/usr/sbin 73 libexecdir=/usr/sbin 74 else 75 bindir="$basedir/bin" 76 if test -z "$datadir" 77 then 78 datadir="$basedir/data" 79 fi 80 sbindir="$basedir/sbin" 81 libexecdir="$basedir/libexec" 82 fi 83 84 # datadir_set is used to determine if datadir was set (and so should be 85 # *not* set inside of the --basedir= handler.) 86 datadir_set= 87 88 # 89 # Use LSB init script functions for printing messages, if possible 90 # 91 lsb_functions="/lib/lsb/init-functions" #linux系统脚本,包含打印log函数 92 if test -f $lsb_functions ; then #如果存在改文件,将这些函数导入该脚本 93 . $lsb_functions 94 else #否则使用自定义信息 95 log_success_msg() 96 { 97 echo " SUCCESS! $@" 98 } 99 log_failure_msg()100 {101 echo " ERROR! $@"102 }103 fi104 105 PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin" #添加$basrdir到系统环境变量106 export PATH107 108 mode=$1 # start or Stop #传入启动脚本的第1个参数109 110 [ $# -ge 1 ] && shift #如果参数个数大于等于1个,shift删掉第一个参数,将剩余参数传给$other_args111 112 113 other_args="$*" # uncommon, but needed when called from an RPM upgrade action114 # Expected: "--skip-networking --skip-grant-tables"115 # They are not checked here, intentionally, as it is the resposibility116 # of the "spec" file author to give correct arguments only.117 118 case `echo "testing\c"`,`echo -n testing` #echo_c和echo_n的定义;\c不加换行符,-n不换行119 *c*,-n*) echo_n= echo_c= ;;120 *c*,*) echo_n=-n echo_c= ;;121 *) echo_n= echo_c=‘\c‘ ;;122 esac123 124 125 parse_server_arguments() { #该函数将my_print_defaults 命令分析出得参数赋值给相应的变量126 for arg do 127 case "$arg" in128 --basedir=*) basedir=`echo "$arg" | sed -e ‘s/^[^=]*=//‘` #利用正则表达式获取129 bindir="$basedir/bin"130 if test -z "$datadir_set"; then 131 datadir="$basedir/data"132 fi133 sbindir="$basedir/sbin"134 libexecdir="$basedir/libexec"135 ;;136 --datadir=*) datadir=`echo "$arg" | sed -e ‘s/^[^=]*=//‘`137 datadir_set=1138 ;;139 --pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e ‘s/^[^=]*=//‘` ;;140 --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e ‘s/^[^=]*=//‘` ;;141 esac142 done143 }144 145 146 147 wait_for_pid () { #该函数在启动和停止mysql服务时用于等待pid的生成148 verb="$1" # created | removed149 pid="$2" # process ID of the program operating on the pid-file150 pid_file_path="$3" # path to the PID file.151 152 i=0153 avoid_race_condition="by checking again"154 155 while test $i -ne $service_startup_timeout ; do 156 157 case "$verb" in #处理第1个参数,created或removed158 ‘created‘)159 # wait for a PID-file to pop into existence.160 test -s "$pid_file_path" && i=‘‘ && break161 ;;162 ‘removed‘)163 # wait for this PID-file to disappear164 test ! -s "$pid_file_path" && i=‘‘ && break165 ;;166 *)167 echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path"168 exit 1169 ;;170 esac171 172 # if server isn‘t running, then pid-file will never be updated173 if test -n "$pid"; then #如果pid非空174 if kill -0 "$pid" 2>/dev/null; then #kill -0发送一个无效信号,可检查进程是否存在,存在返回0,反之则1175 : # the server still runs176 else177 # The server may have exited between the last pid-file check and now. 178 if test -n "$avoid_race_condition"; then179 avoid_race_condition=""180 continue # Check again.181 fi182 183 # there‘s nothing that will affect the file.184 log_failure_msg "The server quit without updating PID file ($pid_file_path)."185 return 1 # not waiting any more.186 fi187 fi188 189 echo $echo_n ".$echo_c" 190 i=`expr $i + 1`191 sleep 1 #睡眠1秒192 193 done194 195 if test -z "$i" ; then #如果i长度为0196 log_success_msg197 return 0198 else199 log_failure_msg200 return 1201 fi202 }203 204 205 # Get arguments from the my.cnf file,206 # the only group, which is read from now on is [mysqld]207 if test -x ./bin/my_print_defaults #找到print_defaults的路径208 then209 print_defaults="./bin/my_print_defaults"210 elif test -x $bindir/my_print_defaults211 then212 print_defaults="$bindir/my_print_defaults"213 elif test -x $bindir/mysql_print_defaults214 then215 print_defaults="$bindir/mysql_print_defaults"216 else217 # Try to find basedir in /etc/my.cnf218 conf=/etc/my.cnf219 print_defaults=220 if test -r $conf #如果可读,从配置文件$conf读取221 then222 subpat=‘^[^=]*basedir[^=]*=\(.*\)$‘223 dirs=`sed -e "/$subpat/!d" -e ‘s//\1/‘ $conf`224 for d in $dirs225 do226 d=`echo $d | sed -e ‘s/[ ]//g‘`227 if test -x "$d/bin/my_print_defaults"228 then229 print_defaults="$d/bin/my_print_defaults"230 break231 fi232 if test -x "$d/bin/mysql_print_defaults"233 then234 print_defaults="$d/bin/mysql_print_defaults"235 break236 fi237 done238 fi239 240 # Hope it‘s in the PATH ... but I doubt it241 test -z "$print_defaults" && print_defaults="my_print_defaults" #还是不行,就用my_print_defaults242 fi243 244 #245 # Read defaults file from ‘basedir‘. If there is no defaults file there246 # check if it‘s in the old (depricated) place (datadir) and read it from there247 #248 249 #配置文件的目录,先从basedir读取,不行再读取datadir的250 extra_args=""251 if test -r "$basedir/my.cnf"252 then253 extra_args="-e $basedir/my.cnf"254 else255 if test -r "$datadir/my.cnf"256 then257 extra_args="-e $datadir/my.cnf"258 fi259 fi260 261 #使用parse_server_arguments函数和my_print_defaults 从my.cnf 中获取相应的参数并付给相应的变量262 parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`263 264 #265 # Set pid file if not given266 #指定mysql启动时进程文件的位置267 if test -z "$mysqld_pid_file_path"268 then269 mysqld_pid_file_path=$datadir/`hostname`.pid270 else271 case "$mysqld_pid_file_path" in272 /* ) ;;273 * ) mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;;274 esac275 fi276 277 case "$mode" in278 ‘start‘)279 # Start daemon280 281 # Safeguard (relative paths, core dumps..)282 cd $basedir283 284 echo $echo_n "Starting MySQL"285 if test -x $bindir/mysqld_safe #如果mysqld_safe存在且可执行286 then287 # Give extra arguments to mysqld with the my.cnf file. This script288 # may be overwritten at next upgrade.289 #关键语句,启动mysqld_safe,传入3个参数:datadir,pid-file,other_args;将输出丢弃到系统黑洞/dev/null290 $bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &291 wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=http://www.mamicode.com/$?"color: #800000;">292 293 # Make lock for RedHat / SuSE #mysql锁的检测和创建294 if test -w "$lockdir" #如果存在且可写295 then296 touch "$lock_file_path"297 fi298 299 exit $return_value300 else301 log_failure_msg "Couldn‘t find MySQL server ($bindir/mysqld_safe)"302 fi303 ;;304 305 ‘stop‘)306 # Stop daemon. We use a signal here to avoid having to know the307 # root password.308 309 if test -s "$mysqld_pid_file_path" #如果非空310 then311 mysqld_pid=`cat "$mysqld_pid_file_path"` #获取mysqld进程312 313 if (kill -0 $mysqld_pid 2>/dev/null)314 then315 echo $echo_n "Shutting down MySQL"316 kill $mysqld_pid #杀死317 # mysqld should remove the pid file when it exits, so wait for it.318 wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=http://www.mamicode.com/$?"color: #800000;">319 else320 log_failure_msg "MySQL server process #$mysqld_pid is not running!"321 rm "$mysqld_pid_file_path"322 fi323 324 # Delete lock for RedHat / SuSE325 if test -f "$lock_file_path" #如果存在锁,需要移除326 then327 rm -f "$lock_file_path"328 fi329 exit $return_value330 else331 log_failure_msg "MySQL server PID file could not be found!"332 fi333 ;;334 335 ‘restart‘) 336 # Stop the service and regardless of whether it was #重启mysql337 # running or not, start it again.338 if $0 stop $other_args; then339 $0 start $other_args340 else341 log_failure_msg "Failed to stop running server, so refusing to try to start."342 exit 1343 fi344 ;;345 346 ‘reload‘|‘force-reload‘) #重载mysql347 if test -s "$mysqld_pid_file_path" ; then348 read mysqld_pid < "$mysqld_pid_file_path"349 kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL"350 touch "$mysqld_pid_file_path"351 else352 log_failure_msg "MySQL PID file could not be found!"353 exit 1354 fi355 ;;356 ‘status‘) 357 # First, check to see if pid file exists #mysql的状态 358 if test -s "$mysqld_pid_file_path" ; then 359 read mysqld_pid < "$mysqld_pid_file_path"360 if kill -0 $mysqld_pid 2>/dev/null ; then 361 log_success_msg "MySQL running ($mysqld_pid)"362 exit 0363 else364 log_failure_msg "MySQL is not running, but PID file exists"365 exit 1366 fi367 else368 # Try to find appropriate mysqld process 369 mysqld_pid=`pidof $libexecdir/mysqld`370 371 # test if multiple pids exist372 pid_count=`echo $mysqld_pid | wc -w`373 if test $pid_count -gt 1 ; then374 log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)"375 exit 5376 elif test -z $mysqld_pid ; then 377 if test -f "$lock_file_path" ; then 378 log_failure_msg "MySQL is not running, but lock file ($lock_file_path) exists"379 exit 2380 fi 381 log_failure_msg "MySQL is not running"382 exit 3383 else384 log_failure_msg "MySQL is running but PID file could not be found"385 exit 4386 fi387 fi388 ;;389 *)390 # usage #输出用法的提示391 basename=`basename "$0"`392 echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]"393 exit 1394 ;;395 esac396 397 exit 0
mysql启动脚本详解
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