深度解析MySQL啓動時報「The server quit without updating PID file」錯誤的緣由
不少童鞋在啓動mysql的時候，碰到過這個錯誤，html
首先，澄清一點，出現這個錯誤的前提是：經過服務腳原本啓動mysql。經過mysqld_safe或mysqld啓動mysql實例並不會報這個錯誤。mysql
那麼，出現這個錯誤的緣由具體是什麼呢？linux
哈哈，對分析過程不care的童鞋可直接跳到文末的總結部分~sql
總結 shell
下面，來分析下mysql的服務啓動腳本數據庫
腳本完整內容以下：安全
#!/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" $other_args >/dev/null 2>&1 & wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$? # Make lock for RedHat / SuSE if test -w "$lockdir" then touch "$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" "$mysqld_pid_file_path"; return_value=$? else log_failure_msg "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: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]" exit 1 ;; esac exit 0
首先，定義相關參數服務器
basedir= datadir= # Default value, in seconds, afterwhich the script should timeout waiting # for server start. # Value here is overriden by value in my.cnf. # 0 means don't wait at all # Negative numbers mean to wait indefinitely service_startup_timeout=900 # Lock directory for RedHat / SuSE. lockdir='/var/lock/subsys' lock_file_path="$lockdir/mysql"
其中，app
basedir 指的二進制壓縮包解壓後所在的目錄，譬如/usr/local/mysql。less
datadir 指的是數據目錄
service_startup_timeout=900 定義mysql服務啓動的時間限制，若是在900s中沒有啓動成功，則該腳本會退出。
lockdir='/var/lock/subsys'
關於/var/lock/subsys，網上的解釋以下，後續會用到。
總的來講，系統關閉的過程（發出關閉信號，調用服務自身的進程）中會檢查/var/lock/subsys下的文件，逐一關閉每一個服務，若是某一運行的服務在/var/lock/subsys下沒有相應的選項。在系統關閉的時候，會像殺死普通進程同樣殺死這個服務。 經過察看/etc/rc.d/init.d下的腳本，能夠發現每一個服務本身操縱時都會去查看/var/lock/subsys下相應的服務。 不少程序須要判斷是否當前已經有一個實例在運行，這個目錄就是讓程序判斷是否有實例運行的標誌，好比說xinetd，若是存在這個文件，表示已經有xinetd在運行了，不然就是沒有，固然程序裏面還要有相應的判斷措施來真正肯定是否有實例在運行。一般與該目錄配套的還有/var/run目錄，用來存放對應實例的PID，若是你寫腳本的話，會發現這2個目錄結合起來能夠很方便的判斷出許多服務是否在運行，運行的相關信息等等。
判斷basedir和datadir
# 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="$basedir/libexec" fi
其中，
mysqld_pid_file_path 指定pid文件的路徑
-z string 判斷字符串是否爲空
若是basedir沒有顯示設置，則默認爲/usr/local/mysql，這也是爲何不少mysql安裝教程都推薦將mysql相關文件放到/usr/local/mysql下。
若是datadir沒有顯示設置，則默認爲$basedir/data。
定義log_success_msg()和log_failure_msg()函數
首先，判斷/lib/lsb/init-functions文件是否存在，若是存在，則使定義在init-functions文件中的全部shell函數在當前腳本中生效。
若是沒有，則定義兩個函數，一個用於打印成功日誌，一個是打印錯誤日誌。
在RHCS 6.7中，該文件並不存在，已被/etc/init.d/functions所替代。
# # 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! $@" } fi
傳遞參數
將第一個參數傳遞給mode，剩下的參數傳遞給other_args
PATH="/sbin:/usr/sbin:/bin:/usr/bin:$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
解析配置文件中的參數
這個函數在腳本後面會涉及到。
主要涉及以下參數：--basedir，--datadir，--pid-file，--service-startup-timeout。
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 }
判斷my_print_defaults的位置
首先，它判斷當前路徑下的bin目錄中是否存在該可執行文件，若是不存在，則再判斷$bindir（一般指的是$basedir/bin）目錄下是否存在。
若是仍是沒有，則會判斷/etc/my.cnf是否存在而且可讀，若是是，則判斷該配置文件中是否指定了basedir參數，
若是指定了，則取出該參數的值，並判斷該值對應的目錄中是否存在bin/my_print_defaults可執行文件
最後一步，若是在上述目錄中實在沒發現my_print_defaults文件，
索性就將print_defaults設置爲"my_print_defaults"，寄但願於該命令在當前的PATH環境中。
# 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
查找默認的配置文件
-r file 若是文件可讀，則爲真
# # 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 $datadir/my.cnf" fi fi
解析配置文件中的參數
my_print_defaults的用法以下：
my_print_defaults --defaults-file=example.cnf client mysql
即讀取配置文件中，client和mysql部分的參數配置，
具體在本腳本中，是讀取mysqld，server，mysql_server，mysql.server四個部分的配置參數。
parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`
設置pid file的路徑
-z string 判斷字符串是否爲空
若是--pid-file沒有在讀取到的配置文件中設置或者腳本剛開始的mysqld_pid_file_path參數沒有設置，
則pid file默認設置在datadir下，以主機名.pid命名。
若是該參數設置了，還須要進一步判斷
若是該參數中帶有斜槓，則表明給定的值帶有路徑，可直接使用。
若是該參數中沒帶路徑，則表明給定的值只是pid的文件名，可將其設在datadir下。
# # Set pid file if not given # if test -z "$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
服務腳本start選項
首先，切換到$basedir中
其次，判斷$basedir/bin中的mysqld_safe是不是可執行文件，若是是，則啓動mysqld實例，若是不是，則報錯退出。
那麼，啓動流程又是如何實現的呢？
首先，執行$bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &命令，啓動mysqld實例。
注意到沒有，mysqld_safe實際上是在basedir中執行的，包括mysql初始化腳本mysql_install_db，也建議在basedir中執行，具體可參考：
分析MariaDB初始化腳本mysql_install_db
而後經過wait_for_pid函數進行判斷，具體可見下文對於wait_for_pid函數的分析
判斷完畢後，
查看$lockdir目錄是否可寫，可寫的話，則在目錄上建立一個文件。
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" $other_args >/dev/null 2>&1 & wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$? # Make lock for RedHat / SuSE if test -w "$lockdir" then touch "$lock_file_path" fi exit $return_value else log_failure_msg "Couldn't find MySQL server ($bindir/mysqld_safe)" fi ;;
wait_for_pid函數
在利用mysqld_safe啓動mysql實例後，會調用該參數
wait_for_pid created "$!" "$mysqld_pid_file_path"; return_value=$?
其中$!在shell中用於獲取最後運行的後臺Process的PID，具體在本例中，是mysqld_safe進程的pid。
由於第一個參數是created，因此會執行test -s "$pid_file_path" && i='' && break命令。
-s file 若是文件的長度不爲零，則爲真
該命令的意思是若是pid文件存在，則將變量i設置爲空，並退出while循環。
而後執行以下判斷，
if test -z "$i" ; then log_success_msg return 0 else log_failure_msg return 1 fi
若是$i爲空，則打印成功日誌，並退出腳本，很顯然，在pid文件存在的狀況下，會將變量i設置爲空。
再來看看pid文件不存在的狀況
首先，會判斷$pid是否不爲空（即if test -n "$pid"）
若是不爲空，則表明在執行完mysqld_safe後，已經捕捉到了該進程的pid。
在這種狀況下，進一步經過kill -0 "$pid"確認該進程是否存在。
kill -0就是不發送任何信號,可是系統會進行錯誤檢查,因此常常用來檢查一個進程是否存在,當進程不存在時, kill -0 pid會返回錯誤
若是該進程存在，則不執行任何操做，直接跳到以下操做
echo $echo_n ".$echo_c" i=`expr $i + 1` sleep 1
將變量i加1，並sleep 1s。
而後，繼續while循環，之因此這樣作，是考慮到mysqld_safe已經執行，可是mysqld實例還在啓動過程當中，還沒建立好pid文件。
一直到$1達到$service_startup_timeout定義的時長。
若是在while循環的過程當中，經過kill -0 "$pid"判斷到進程已經不存在了，
則會再判斷一次，若是此次判斷的結果依舊是pid file不存在，且進程不存在，則會執行
log_failure_msg "The server quit without updating PID file ($pid_file_path)."
這就是大名鼎鼎的「The server quit without updating PID file」的由來。
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 }
服務腳本stop選項
首先，判斷pid文件的長度是否不爲零。
-s file 若是文件的長度不爲零，則爲真
此時，會經過pid文件獲取mysqld進程的pid，注意，不是mysqld_safe進程的pid
而後，判斷mysqld進程是否在正常運行，
若是是，則經過kill $mysqld_pid的方式來關閉mysqld進程
殺死進程最安全的方法是單純使用kill命令，不加修飾符，不帶標誌。
標準的kill命令一般會終止有問題的進程，並把進程的資源釋放給系統。然而，若是進程啓動了子進程，只殺死父進程，子進程仍在運行，所以仍消耗資源。爲了防止這些所謂的「殭屍進程」，應確保在殺死父進程以前，先殺死其全部的子進程。
而後，調用wait_for_pid函數進行判斷，其實，wait_for_pid函數中設置avoid_race_condition變量的目的是爲了stop選項，確實有可能出現，mysqld是在檢查pid file以後，檢查進程是否存活以前退出的。
若是mysqld進程沒有正常運行，在會打印「MySQL server process #$mysqld_pid is not running!」信息，並刪除pid文件。
若是在執行stop的時候，判斷pid文件的長度爲0，則會打印"MySQL server PID file could not be found!"信息。
因此，在pid文件不存在的狀況下，經過服務腳本執行stop選項並不會關閉mysqld進程，這個時候，就可經過kill $mysqld_pid的方式來關閉mysqld進程。
'stop') # Stop daemon. We use a signal here to avoid having to know the # root password. if test -s "$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" "$mysqld_pid_file_path"; return_value=$? else log_failure_msg "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 ;;
服務腳本restart選項
首先，先執行stop操做，若是stop操做成功的話，則繼續執行start操做。
若是stop操做失敗的話，則會輸出"Failed to stop running server, so refusing to try to start."信息，並退出腳本。
'restart') # Stop the service and regardless of whether it was # running or not, start it again. if $0 stop $other_args; then $0 start $other_args else log_failure_msg "Failed to stop running server, so refusing to try to start." exit 1 fi ;;
服務腳本reload選項
首先，判斷pid文件的長度是否爲0，若是不爲0，則將該文件中的值設置爲mysqld_pid變量的值。
而後對該進程執行kill -HUP操做。
kill -HUP pid pid 是進程標識。若是想要更改配置而不需中止並從新啓動服務，請使用該命令。在對配置文件做必要的更改後，發出該命令以動態更新服務配置。 根據約定，當您發送一個掛起信號（信號 1 或 HUP）時，大多數服務器進程（全部經常使用的進程）都會進行復位操做並從新加載它們的配置文件。
若是pid文件的長度爲0，則輸出"MySQL PID file could not be found!"。
'reload'|'force-reload') if test -s "$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 ;;
服務腳本status選項
首先，判斷pid文件長度是否爲0，若是不是，則讀取該文件中的值，並判斷pid對應的進程是否運行正常，
若是運行正常，則輸出"MySQL running"
若是不正常，則輸出"MySQL is not running, but PID file exists"
若是pid文件的長度爲0，則試圖經過mysqld的啓動命令來獲取其pid，
這個時候，可能存在一個mysqld程序啓動了多個實例，這會致使pid_count=`echo $mysqld_pid | wc -w`大於1。
這個時候，會輸出"Multiple MySQL running but PID file could not be found"信息，並退出腳本。
若是mysqld_pid爲空，則會繼續判斷"$lock_file_path"是否存在，若是存在，
則會輸出"MySQL is not running, but lock file ($lock_file_path) exists"信息。
若是"$lock_file_path"不存在，則會輸出"MySQL is not running"信息。
若是mysqld_pid等於1，則會輸出"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 ;;
服務腳本其它選項
若是腳本的第一個參數不是上述幾個選項，則會輸出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的服務腳本分析完畢~
總結
在經過服務腳本啓動mysql的過程當中，報「The server quit without updating PID file」錯誤，有兩個條件
首先，pid文件不存在
其次，經過kill -0 $pid檢查到進程並不存在
這個時候，只能經過mysql數據庫的錯誤日誌來定位。
服務腳本若是不作任何調整的話，默認的basedir是/usr/local/mysql，datadir是/usr/local/mysql/data
若是本身的mysql服務不是默認路徑，
則須要在該腳本中顯式設置
經測試，需設置以下幾處：
1. 設置basedir和添加conf變量
其中，conf指的是mysqld的配置文件，建議配置文件中顯式指定basedir和datadir的值。
在這裏，datadir可不設置，由於datadir可經過配置文件來獲取。
可是basedir必需要指定，由於要首先根據basedir來判斷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的啓動參數
將
$bindir/mysqld_safe --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &
修改成，
$bindir/mysqld_safe --defaults-file="$conf" --datadir="$datadir" --pid-file="$mysqld_pid_file_path" $other_args >/dev/null 2>&1 &
主要是添加了--defaults-file選項
參考
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