mysql启动脚本详解

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" $other_args >/dev/null 2>&1 &291       wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$?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" "$mysqld_pid_file_path"; return_value=$?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

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