#!/bin/sh
# Copyright Abandoned 1996 TCX DataKonsult AB & Monty Program KB & Detron HB
# This file is public domain and comes with NO WARRANTY of any kind
# MySQL daemon start/stop script.
# Usually this is put in /etc/init.d (at least on machines SYSV R4 based
# systems) and linked to /etc/rc3.d/S99mysql and /etc/rc0.d/K01mysql.
# When this is done the mysql server will be started when the machine is
# started and shut down when the systems goes down.
# Comments to support chkconfig on RedHat Linux
# chkconfig: 2345 64 36
# description: A very fast and reliable SQL database engine.
# Comments to support LSB init script conventions
### BEGIN INIT INFO
# Provides: mysql
# Required-Start: $local_fs $network $remote_fs
# Should-Start: ypbind nscd ldap ntpd xntpd
# Required-Stop: $local_fs $network $remote_fs
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: start and stop MySQL
# Description: MySQL is a very fast and reliable SQL database engine.
### END INIT INFO
# If you install MySQL on some other places than /usr/local/mysql, then you
# have to do one of the following things for this script to work:
#
# - Run this script from within the MySQL installation directory
# - Create a /etc/my.cnf file with the following information:
# [mysqld]
# basedir=<path-to-mysql-installation-directory>
# - Add the above to any other configuration file (for example ~/.my.ini)
# and copy my_print_defaults to /usr/bin
# - Add the path to the mysql-installation-directory to the basedir variable
# below.
#
# If you want to affect other MySQL variables, you should make your changes
# in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files.
# If you change base dir, you must also change datadir. These may get
# overwritten by settings in the MySQL configuration files.
basedir=
datadir=
# Default value, in seconds, afterwhich the script should timeout waiting
# for server start. 
# Value here is overriden by value in my.cnf. 
# 0 means don't wait at all
# Negative numbers mean to wait indefinitely
service_startup_timeout=900
# Lock directory for RedHat / SuSE.
lockdir='/var/lock/subsys'
lock_file_path="$lockdir/mysql"
# The following variables are only set for letting mysql.server find things.
# Set some defaults
mysqld_pid_file_path=
if test -z "$basedir"
then
 basedir=/usr/local/mysql
 bindir=/usr/local/mysql/bin
 if test -z "$datadir"
 then
 datadir=/usr/local/mysql/data
 fi
 sbindir=/usr/local/mysql/bin
 libexecdir=/usr/local/mysql/bin
else
 bindir="$basedir/bin"
 if test -z "$datadir"
 then
 datadir="$basedir/data"
 fi
 sbindir="$basedir/sbin"
 libexecdir="$basedir/libexec"
fi
# datadir_set is used to determine if datadir was set (and so should be
# *not* set inside of the --basedir= handler.)
datadir_set=
#
# Use LSB init script functions for printing messages, if possible
#
lsb_functions="/lib/lsb/init-functions"
if test -f $lsb_functions ; then
 . $lsb_functions
else
 log_success_msg()
 {
 echo " SUCCESS! $@"
 }
 log_failure_msg()
 {
 echo " ERROR! $@"
 }
fi
PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"
export PATH
mode=$1 # start or stop
[ $# -ge 1 ] && shift
other_args="$*" # uncommon, but needed when called from an RPM upgrade action
   # Expected: "--skip-networking --skip-grant-tables"
   # They are not checked here, intentionally, as it is the resposibility
   # of the "spec" file author to give correct arguments only.
case `echo "testing\c"`,`echo -n testing` in
 *c*,-n*) echo_n= echo_c=  ;;
 *c*,*) echo_n=-n echo_c=  ;;
 *)  echo_n= echo_c='\c' ;;
esac
parse_server_arguments() {
 for arg do
 case "$arg" in
  --basedir=*) basedir=`echo "$arg" | sed -e 's/^[^=]*=//'`
     bindir="$basedir/bin"
   if test -z "$datadir_set"; then
    datadir="$basedir/data"
   fi
   sbindir="$basedir/sbin"
   libexecdir="$basedir/libexec"
  ;;
  --datadir=*) datadir=`echo "$arg" | sed -e 's/^[^=]*=//'`
   datadir_set=1
 ;;
  --pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
  --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
 esac
 done
}
wait_for_pid () {
 verb="$1"   # created | removed
 pid="$2"   # process ID of the program operating on the pid-file
 pid_file_path="$3" # path to the PID file.
 i=0
 avoid_race_condition="by checking again"
 while test $i -ne $service_startup_timeout ; do
 case "$verb" in
  'created')
  # wait for a PID-file to pop into existence.
  test -s "$pid_file_path" && i='' && break
  ;;
  'removed')
  # wait for this PID-file to disappear
  test ! -s "$pid_file_path" && i='' && break
  ;;
  *)
  echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path"
  exit 1
  ;;
 esac
 # if server isn't running, then pid-file will never be updated
 if test -n "$pid"; then
  if kill -0 "$pid" 2>/dev/null; then
  : # the server still runs
  else
  # The server may have exited between the last pid-file check and now. 
  if test -n "$avoid_race_condition"; then
   avoid_race_condition=""
   continue # Check again.
  fi
  # there's nothing that will affect the file.
  log_failure_msg "The server quit without updating PID file ($pid_file_path)."
  return 1 # not waiting any more.
  fi
 fi
 echo $echo_n ".$echo_c"
 i=`expr $i + 1`
 sleep 1
 done
 if test -z "$i" ; then
 log_success_msg
 return 0
 else
 log_failure_msg
 return 1
 fi
}
# Get arguments from the my.cnf file,
# the only group, which is read from now on is [mysqld]
if test -x ./bin/my_print_defaults
then
 print_defaults="./bin/my_print_defaults"
elif test -x $bindir/my_print_defaults
then
 print_defaults="$bindir/my_print_defaults"
elif test -x $bindir/mysql_print_defaults
then
 print_defaults="$bindir/mysql_print_defaults"
else
 # Try to find basedir in /etc/my.cnf
 conf=/etc/my.cnf
 print_defaults=
 if test -r $conf
 then
 subpat='^[^=]*basedir[^=]*=\(.*\)$'
 dirs=`sed -e "/$subpat/!d" -e 's//\1/' $conf`
 for d in $dirs
 do
  d=`echo $d | sed -e 's/[  ]//g'`
  if test -x "$d/bin/my_print_defaults"
  then
  print_defaults="$d/bin/my_print_defaults"
  break
  fi
  if test -x "$d/bin/mysql_print_defaults"
  then
  print_defaults="$d/bin/mysql_print_defaults"
  break
  fi
 done
 fi
 # Hope it's in the PATH ... but I doubt it
 test -z "$print_defaults" && print_defaults="my_print_defaults"
fi
#
# Read defaults file from 'basedir'. If there is no defaults file there
# check if it's in the old (depricated) place (datadir) and read it from there
#
extra_args=""
if test -r "$basedir/my.cnf"
then
 extra_args="-e $basedir/my.cnf"
else
 if test -r "$datadir/my.cnf"
 then
 extra_args="-e $datadir/my.cnf"
 fi
fi
parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`
#
# Set pid file if not given
#
if test -z "$mysqld_pid_file_path"
then
 mysqld_pid_file_path=$datadir/`hostname`.pid
else
 case "$mysqld_pid_file_path" in
 /* ) ;;
 * ) mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;;
 esac
fi
case "$mode" in
 'start')
 # Start daemon
 # Safeguard (relative paths, core dumps..)
 cd $basedir
 echo $echo_n "Starting MySQL"
 if test -x $bindir/mysqld_safe
 then
  # Give extra arguments to mysqld with the my.cnf file. This script
  # may be overwritten at next upgrade.
  $bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &
  wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$"$lockdir"
  then
  touch "$lock_file_path"
  fi
  exit $return_value
 else
  log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)"
 fi
 ;;
 'stop')
 # Stop daemon. We use a signal here to avoid having to know the
 # root password.
 if test -s "$mysqld_pid_file_path"
 then
  mysqld_pid=`cat "$mysqld_pid_file_path"`
  if (kill -0 $mysqld_pid 2>/dev/null)
  then
  echo $echo_n "Shutting down MySQL"
  kill $mysqld_pid
  # mysqld should remove the pid file when it exits, so wait for it.
  wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=$"MySQL server process #$mysqld_pid is not running!"
  rm "$mysqld_pid_file_path"
  fi
  # Delete lock for RedHat / SuSE
  if test -f "$lock_file_path"
  then
  rm -f "$lock_file_path"
  fi
  exit $return_value
 else
  log_failure_msg "MySQL server PID file could not be found!"
 fi
 ;;
 'restart')
 # Stop the service and regardless of whether it was
 # running or not, start it again.
 if $0 stop $other_args; then
  $0 start $other_args
 else
  log_failure_msg "Failed to stop running server, so refusing to try to start."
  exit 1
 fi
 ;;
 'reload'|'force-reload')
 if test -s "$mysqld_pid_file_path" ; then
  read mysqld_pid < "$mysqld_pid_file_path"
  kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL"
  touch "$mysqld_pid_file_path"
 else
  log_failure_msg "MySQL PID file could not be found!"
  exit 1
 fi
 ;;
 'status')
 # First, check to see if pid file exists
 if test -s "$mysqld_pid_file_path" ; then 
  read mysqld_pid < "$mysqld_pid_file_path"
  if kill -0 $mysqld_pid 2>/dev/null ; then 
  log_success_msg "MySQL running ($mysqld_pid)"
  exit 0
  else
  log_failure_msg "MySQL is not running, but PID file exists"
  exit 1
  fi
 else
  # Try to find appropriate mysqld process
  mysqld_pid=`pidof $libexecdir/mysqld`
  # test if multiple pids exist
  pid_count=`echo $mysqld_pid | wc -w`
  if test $pid_count -gt 1 ; then
  log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)"
  exit 5
  elif test -z $mysqld_pid ; then 
  if test -f "$lock_file_path" ; then 
   log_failure_msg "MySQL is not running, but lock file ($lock_file_path) exists"
   exit 2
  fi 
  log_failure_msg "MySQL is not running"
  exit 3
  else
  log_failure_msg "MySQL is running but PID file could not be found"
  exit 4
  fi
 fi
 ;;
 *)
  # usage
  basename=`basename "$0"`
  echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]"
  exit 1
 ;;
esac
exit 0

basedir=
datadir=
# Default value, in seconds, afterwhich the script should timeout waiting
# for server start. 
# Value here is overriden by value in my.cnf. 
# 0 means don't wait at all
# Negative numbers mean to wait indefinitely
service_startup_timeout=900
# Lock directory for RedHat / SuSE.
lockdir='/var/lock/subsys'
lock_file_path="$lockdir/mysql"

lockdir='/var/lock/subsys'

# Set some defaults
mysqld_pid_file_path=
if test -z "$basedir"
then
 basedir=/usr/local/mysql
 bindir=/usr/local/mysql/bin
 if test -z "$datadir"
 then
 datadir=/usr/local/mysql/data
 fi
 sbindir=/usr/local/mysql/bin
 libexecdir=/usr/local/mysql/bin
else
 bindir="$basedir/bin"
 if test -z "$datadir"
 then
 datadir="$basedir/data"
 fi
 sbindir="$basedir/sbin"
 libexecdir="$basedir/libexec"
fi

#
# Use LSB init script functions for printing messages, if possible
#
lsb_functions="/lib/lsb/init-functions"
if test -f $lsb_functions ; then
 . $lsb_functions
else
 log_success_msg()
 {
 echo " SUCCESS! $@"
 }
 log_failure_msg()
 {
 echo " ERROR! $@"
 }
fi

PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin"
export PATH
mode=$1 # start or stop
[ $# -ge 1 ] && shift
other_args="$*" # uncommon, but needed when called from an RPM upgrade action
   # Expected: "--skip-networking --skip-grant-tables"
   # They are not checked here, intentionally, as it is the resposibility
   # of the "spec" file author to give correct arguments only.
case `echo "testing\c"`,`echo -n testing` in
 *c*,-n*) echo_n= echo_c=  ;;
 *c*,*) echo_n=-n echo_c=  ;;
 *)  echo_n= echo_c='\c' ;;
esac

parse_server_arguments() {
 for arg do
 case "$arg" in
  --basedir=*) basedir=`echo "$arg" | sed -e 's/^[^=]*=//'`
     bindir="$basedir/bin"
   if test -z "$datadir_set"; then
    datadir="$basedir/data"
   fi
   sbindir="$basedir/sbin"
   libexecdir="$basedir/libexec"
  ;;
  --datadir=*) datadir=`echo "$arg" | sed -e 's/^[^=]*=//'`
   datadir_set=1
 ;;
  --pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
  --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e 's/^[^=]*=//'` ;;
 esac
 done
}

# Get arguments from the my.cnf file,
# the only group, which is read from now on is [mysqld]
if test -x ./bin/my_print_defaults
then
 print_defaults="./bin/my_print_defaults"
elif test -x $bindir/my_print_defaults
then
 print_defaults="$bindir/my_print_defaults"
elif test -x $bindir/mysql_print_defaults
then
 print_defaults="$bindir/mysql_print_defaults"
else
 # Try to find basedir in /etc/my.cnf
 conf=/etc/my.cnf
 print_defaults=
 if test -r $conf
 then
 subpat='^[^=]*basedir[^=]*=\(.*\)$'
 dirs=`sed -e "/$subpat/!d" -e 's//\1/' $conf`
 for d in $dirs
 do
  d=`echo $d | sed -e 's/[  ]//g'`
  if test -x "$d/bin/my_print_defaults"
  then
  print_defaults="$d/bin/my_print_defaults"
  break
  fi
  if test -x "$d/bin/mysql_print_defaults"
  then
  print_defaults="$d/bin/mysql_print_defaults"
  break
  fi
 done
 fi
 # Hope it's in the PATH ... but I doubt it
 test -z "$print_defaults" && print_defaults="my_print_defaults"
fi

#
# Read defaults file from 'basedir'. If there is no defaults file there
# check if it's in the old (depricated) place (datadir) and read it from there
#
extra_args=""
if test -r "$basedir/my.cnf"
then
 extra_args="-e $basedir/my.cnf"
else
 if test -r "$datadir/my.cnf"
 then
 extra_args="-e $datadir/my.cnf"
 fi
fi

parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`

#
# Set pid file if not given
#
if test -z "$mysqld_pid_file_path"
then
 mysqld_pid_file_path=$datadir/`hostname`.pid
else
 case "$mysqld_pid_file_path" in
 /* ) ;;
 * ) mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;;
 esac
fi

case "$mode" in
 'start')
 # Start daemon
 # Safeguard (relative paths, core dumps..)
 cd $basedir
 echo $echo_n "Starting MySQL"
 if test -x $bindir/mysqld_safe
 then
  # Give extra arguments to mysqld with the my.cnf file. This script
  # may be overwritten at next upgrade.
  $bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &
  wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$"$lockdir"
  then
  touch "$lock_file_path"
  fi
  exit $return_value
 else
  log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)"
 fi
 ;;

wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$"$pid_file_path" && i='' && break命令。

-s file 如果文件的长度不为零，则为真
该命令的意思是如果pid文件存在，则将变量i设置为空，并退出while循环。
然后执行如下判断，


if test -z "$i" ; then
 log_success_msg
 return 0
 else
 log_failure_msg
 return 1
 fi


如果$i为空，则打印成功日志，并退出脚本，很显然，在pid文件存在的情况下，会将变量i设置为空。
再来看看pid文件不存在的情况
首先，会判断$pid是否不为空（即if test -n "$pid"）
如果不为空，则代表在执行完mysqld_safe后，已经捕捉到了该进程的pid。
在这种情况下，进一步通过kill -0 "$pid"确认该进程是否存在。
kill -0就是不发送任何信号,但是系统会进行错误检查,所以经常用来检查一个进程是否存在,当进程不存在时, kill -0 pid会返回错误
如果该进程存在，则不执行任何操作，直接跳到如下操作


echo $echo_n ".$echo_c"
i=`expr $i + 1`
sleep 1




将变量i加1，并sleep 1s。
然后，继续while循环，之所以这样做，是考虑到mysqld_safe已经执行，但是mysqld实例还在启动过程中，还没创建好pid文件。
一直到$1达到$service_startup_timeout定义的时长。
如果在while循环的过程中，通过kill -0 "$pid"判断到进程已经不存在了，
则会再判断一次，如果这次判断的结果依旧是pid file不存在，且进程不存在，则会执行


log_failure_msg "The server quit without updating PID file ($pid_file_path)."


这就是大名鼎鼎的“The server quit without updating PID file”的由来。


wait_for_pid () {
 verb="$1"   # created | removed
 pid="$2"   # process ID of the program operating on the pid-file
 pid_file_path="$3" # path to the PID file.
 i=0
 avoid_race_condition="by checking again"
 while test $i -ne $service_startup_timeout ; do
 case "$verb" in
  'created')
  # wait for a PID-file to pop into existence.
  test -s "$pid_file_path" && i='' && break
  ;;
  'removed')
  # wait for this PID-file to disappear
  test ! -s "$pid_file_path" && i='' && break
  ;;
  *)
  echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path"
  exit 1
  ;;
 esac
 # if server isn't running, then pid-file will never be updated
 if test -n "$pid"; then
  if kill -0 "$pid" 2>/dev/null; then
  : # the server still runs
  else
  # The server may have exited between the last pid-file check and now. 
  if test -n "$avoid_race_condition"; then
   avoid_race_condition=""
   continue # Check again.
  fi
  # there's nothing that will affect the file.
  log_failure_msg "The server quit without updating PID file ($pid_file_path)."
  return 1 # not waiting any more.
  fi
 fi
 echo $echo_n ".$echo_c"
 i=`expr $i + 1`
 sleep 1
 done
 if test -z "$i" ; then
 log_success_msg
 return 0
 else
 log_failure_msg
 return 1
 fi
}


服务脚本stop选项
首先，判断pid文件的长度是否不为零。
-s file 如果文件的长度不为零，则为真
此时，会通过pid文件获取mysqld进程的pid，注意，不是mysqld_safe进程的pid
然后，判断mysqld进程是否在正常运行，
如果是，则通过kill $mysqld_pid的方式来关闭mysqld进程
杀死进程最安全的方法是单纯使用kill命令，不加修饰符，不带标志。


标准的kill命令通常会终止有问题的进程，并把进程的资源释放给系统。然而，如果进程启动了子进程，只杀死父进程，子进程仍在运行，因此仍消耗资源。为了防止这些所谓的“僵尸进程”，应确保在杀死父进程之前，先杀死其所有的子进程。


然后，调用wait_for_pid函数进行判断，其实，wait_for_pid函数中设置avoid_race_condition变量的目的是为了stop选项，确实有可能出现，mysqld是在检查pid file之后，检查进程是否存活之前退出的。
如果mysqld进程没有正常运行，在会打印“MySQL server process #$mysqld_pid is not running!”信息，并删除pid文件。
如果在执行stop的时候，判断pid文件的长度为0，则会打印"MySQL server PID file could not be found!"信息。
所以，在pid文件不存在的情况下，通过服务脚本执行stop选项并不会关闭mysqld进程，这个时候，就可通过kill $mysqld_pid的方式来关闭mysqld进程。


'stop')
 # Stop daemon. We use a signal here to avoid having to know the
 # root password.
 if test -s "$mysqld_pid_file_path"
 then
  mysqld_pid=`cat "$mysqld_pid_file_path"`
  if (kill -0 $mysqld_pid 2>/dev/null)
  then
  echo $echo_n "Shutting down MySQL"
  kill $mysqld_pid
  # mysqld should remove the pid file when it exits, so wait for it.
  wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=$"MySQL server process #$mysqld_pid is not running!"
  rm "$mysqld_pid_file_path"
  fi
  # Delete lock for RedHat / SuSE
  if test -f "$lock_file_path"
  then
  rm -f "$lock_file_path"
  fi
  exit $return_value
 else
  log_failure_msg "MySQL server PID file could not be found!"
 fi
 ;;


服务脚本restart选项
首先，先执行stop操作，如果stop操作成功的话，则继续执行start操作。
如果stop操作失败的话，则会输出"Failed to stop running server, so refusing to try to start."信息，并退出脚本。


 'restart')
 # Stop the service and regardless of whether it was
 # running or not, start it again.
 if $0 stop $other_args; then
  $0 start $other_args
 else
  log_failure_msg "Failed to stop running server, so refusing to try to start."
  exit 1
 fi
 ;;


服务脚本reload选项
首先，判断pid文件的长度是否为0，如果不为0，则将该文件中的值设置为mysqld_pid变量的值。
然后对该进程执行kill -HUP操作。


kill -HUP pid


pid 是进程标识。如果想要更改配置而不需停止并重新启动服务，请使用该命令。在对配置文件作必要的更改后，发出该命令以动态更新服务配置。
根据约定，当您发送一个挂起信号（信号 1 或 HUP）时，大多数服务器进程（所有常用的进程）都会进行复位操作并重新加载它们的配置文件。


如果pid文件的长度为0，则输出"MySQL PID file could not be found!"。


 'reload'|'force-reload')
 if test -s "$mysqld_pid_file_path" ; then
  read mysqld_pid < "$mysqld_pid_file_path"
  kill -HUP $mysqld_pid && log_success_msg "Reloading service MySQL"
  touch "$mysqld_pid_file_path"
 else
  log_failure_msg "MySQL PID file could not be found!"
  exit 1
 fi
 ;;


服务脚本status选项
首先，判断pid文件长度是否为0，如果不是，则读取该文件中的值，并判断pid对应的进程是否运行正常，
如果运行正常，则输出"MySQL running"
如果不正常，则输出"MySQL is not running, but PID file exists"
如果pid文件的长度为0，则试图通过mysqld的启动命令来获取其pid，
这个时候，可能存在一个mysqld程序启动了多个实例，这会导致pid_count=`echo $mysqld_pid | wc -w`大于1。
这个时候，会输出"Multiple MySQL running but PID file could not be found"信息，并退出脚本。
如果mysqld_pid为空，则会继续判断"$lock_file_path"是否存在，如果存在，
则会输出"MySQL is not running, but lock file ($lock_file_path) exists"信息。
如果"$lock_file_path"不存在，则会输出"MySQL is not running"信息。
如果mysqld_pid等于1，则会输出"MySQL is running but PID file could not be found"信息。


 'status')
 # First, check to see if pid file exists
 if test -s "$mysqld_pid_file_path" ; then 
  read mysqld_pid < "$mysqld_pid_file_path"
  if kill -0 $mysqld_pid 2>/dev/null ; then 
  log_success_msg "MySQL running ($mysqld_pid)"
  exit 0
  else
  log_failure_msg "MySQL is not running, but PID file exists"
  exit 1
  fi
 else
  # Try to find appropriate mysqld process
  mysqld_pid=`pidof $libexecdir/mysqld`
  # test if multiple pids exist
  pid_count=`echo $mysqld_pid | wc -w`
  if test $pid_count -gt 1 ; then
  log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)"
  exit 5
  elif test -z $mysqld_pid ; then 
  if test -f "$lock_file_path" ; then 
   log_failure_msg "MySQL is not running, but lock file ($lock_file_path) exists"
   exit 2
  fi 
  log_failure_msg "MySQL is not running"
  exit 3
  else
  log_failure_msg "MySQL is running but PID file could not be found"
  exit 4
  fi
 fi
 ;;


服务脚本其它选项
如果脚本的第一个参数不是上述几个选项，则会输出Usage信息。


 *)
  # usage
  basename=`basename "$0"`
  echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]"
  exit 1
 ;;


至此，mysql的服务脚本分析完毕~
总结
在通过服务脚本启动mysql的过程中，报“The server quit without updating PID file”错误，有两个条件
首先，pid文件不存在
其次，通过kill -0 $pid检查到进程并不存在
这个时候，只能通过mysql数据库的错误日志来定位。
服务脚本如果不做任何调整的话，默认的basedir是/usr/local/mysql，datadir是/usr/local/mysql/data
如果自己的mysql服务均不是默认路径，
则需要在该脚本中显式设置
经测试，需设置如下几处：
1. 设置basedir和添加conf变量
其中，conf指的是mysqld的配置文件，建议配置文件中显式指定basedir和datadir的值。
在这里，datadir可不设置，因为datadir可通过配置文件来获取。
但是basedir必须要指定，因为要首先根据basedir来判断my_print_deefauts命令


basedir=/usr/local/mysql-advanced-5.6.23-linux-glibc2.5-x86_64
datadir=
conf=/usr/local/mysql-advanced-5.6.23-linux-glibc2.5-x86_64/my_3308.cnf 


2. 第256行，添加extra_args=" -c $conf"




extra_args=" -e $basedir/my.cnf.bak"
if test -r "$basedir/my.cnf"
then
 extra_args="-e $basedir/my.cnf"
else
 if test -r "$datadir/my.cnf"
 then
 extra_args="-e $datadir/my.cnf"
 fi
fi
extra_args=" -c $conf"


3. 修改285行mysqld_safe的启动参数
将


 $bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &


修改为，


  $bindir/mysqld_safe --defaults-file="$conf" --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &


主要是添加了--defaults-file选项
以上所述是小编给大家介绍的深度解析MySQL启动时报“The server quit without updating PID file”错误的原因，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！