mysql啓動腳本詳解
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 $remote_fs
22 # Default-Start: 2 3 4 5
23 # Default-Stop: 0 1 6
24 # Short-Description: start and stop MySQL
25 # Description: MySQL is a very fast and reliable SQL database engine.
26 ### END INIT INFO
27
28 # If you install MySQL on some other places than /usr, then you
29 # have to do one of the following things for this script to work:
30 #
31 # - Run this script from within the MySQL installation directory
32 # - Create a /etc/my.cnf file with the following information:
33 # [mysqld]
34 # basedir=<path-to-mysql-installation-directory>
35 # - Add the above to any other configuration file (for example ~/.my.ini)
36 # and copy my_print_defaults to /usr/bin
37 # - Add the path to the mysql-installation-directory to the basedir variable
38 # below.
39 #
40 # If you want to affect other MySQL variables, you should make your changes
41 # in the /etc/my.cnf, ~/.my.cnf or other MySQL configuration files.
42
43 # If you change base dir, you must also change datadir. These may get
44 # overwritten by settings in the MySQL configuration files.
45
46 basedir= #mysql的安裝目錄
47 datadir= #數據存儲路徑
48
49 # Default value, in seconds, afterwhich the script should timeout waiting
50 # for server start.
51 # Value here is overriden by value in my.cnf.
52 # 0 means don‘t wait at all
53 # Negative numbers mean to wait indefinitely
54 service_startup_timeout=900
55
56 # Lock directory for RedHat / SuSE.
57 lockdir=‘/var/lock/subsys‘ #mysql進程鎖
58 lock_file_path="$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 "$basedir" #依次確定$basedir,$datadir,$bindir等路徑
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系統腳本，包含打印log函數
92 if test -f $lsb_functions ; then #如果存在改文件，將這些函數導入該腳本
93 . $lsb_functions
94 else #否則使用自定義信息
95 log_success_msg()
96 {
97 echo " SUCCESS! $@"
98 }
99 log_failure_msg()
100 {
101 echo " ERROR! $@"
102 }
103 fi
104
105 PATH="/sbin:/usr/sbin:/bin:/usr/bin:$basedir/bin" #添加$basrdir到系統環境變量
106 export PATH
107
108 mode=$1 # start or Stop #傳入啓動腳本的第1個參數
109
110 [ $# -ge 1 ] && shift #如果參數個數大於等於1個，shift刪掉第一個參數，將剩餘參數傳給$other_args
111
112
113 other_args="$*" # uncommon, but needed when called from an RPM upgrade action
114 # Expected: "--skip-networking --skip-grant-tables"
115 # They are not checked here, intentionally, as it is the resposibility
116 # of the "spec" file author to give correct arguments only.
117
118 case `echo "testing\c"`,`echo -n testing` #echo_c和echo_n的定義；\c不加換行符，-n不換行
119 *c*,-n*) echo_n= echo_c= ;;
120 *c*,*) echo_n=-n echo_c= ;;
121 *) echo_n= echo_c=‘\c‘ ;;
122 esac
123
124
125 parse_server_arguments() { #該函數將my_print_defaults 命令分析出得參數賦值給相應的變量
126 for arg do
127 case "$arg" in
128 --basedir=*) basedir=`echo "$arg" | sed -e ‘s/^[^=]*=//‘` #利用正則表達式獲取
129 bindir="$basedir/bin"
130 if test -z "$datadir_set"; then
131 datadir="$basedir/data"
132 fi
133 sbindir="$basedir/sbin"
134 libexecdir="$basedir/libexec"
135 ;;
136 --datadir=*) datadir=`echo "$arg" | sed -e ‘s/^[^=]*=//‘`
137 datadir_set=1
138 ;;
139 --pid-file=*) mysqld_pid_file_path=`echo "$arg" | sed -e ‘s/^[^=]*=//‘` ;;
140 --service-startup-timeout=*) service_startup_timeout=`echo "$arg" | sed -e ‘s/^[^=]*=//‘` ;;
141 esac
142 done
143 }
144
145
146
147 wait_for_pid () { #該函數在啓動和停止mysql服務時用於等待pid的生成
148 verb="$1" # created | removed
149 pid="$2" # process ID of the program operating on the pid-file
150 pid_file_path="$3" # path to the PID file.
151
152 i=0
153 avoid_race_condition="by checking again"
154
155 while test $i -ne $service_startup_timeout ; do
156
157 case "$verb" in #處理第1個參數，created或removed
158 ‘created‘)
159 # wait for a PID-file to pop into existence.
160 test -s "$pid_file_path" && i=‘‘ && break
161 ;;
162 ‘removed‘)
163 # wait for this PID-file to disappear
164 test ! -s "$pid_file_path" && i=‘‘ && break
165 ;;
166 *)
167 echo "wait_for_pid () usage: wait_for_pid created|removed pid pid_file_path"
168 exit 1
169 ;;
170 esac
171
172 # if server isn‘t running, then pid-file will never be updated
173 if test -n "$pid"; then #如果pid非空
174 if kill -0 "$pid" 2>/dev/null; then #kill -0發送一個無效信號，可檢查進程是否存在，存在返回0，反之則1
175 : # the server still runs
176 else
177 # The server may have exited between the last pid-file check and now.
178 if test -n "$avoid_race_condition"; then
179 avoid_race_condition=""
180 continue # Check again.
181 fi
182
183 # there‘s nothing that will affect the file.
184 log_failure_msg "The server quit without updating PID file ($pid_file_path)."
185 return 1 # not waiting any more.
186 fi
187 fi
188
189 echo $echo_n ".$echo_c"
190 i=`expr $i + 1`
191 sleep 1 #睡眠1秒
192
193 done
194
195 if test -z "$i" ; then #如果i長度爲0
196 log_success_msg
197 return 0
198 else
199 log_failure_msg
200 return 1
201 fi
202 }
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的路徑
208 then
209 print_defaults="./bin/my_print_defaults"
210 elif test -x $bindir/my_print_defaults
211 then
212 print_defaults="$bindir/my_print_defaults"
213 elif test -x $bindir/mysql_print_defaults
214 then
215 print_defaults="$bindir/mysql_print_defaults"
216 else
217 # Try to find basedir in /etc/my.cnf
218 conf=/etc/my.cnf
219 print_defaults=
220 if test -r $conf #如果可讀，從配置文件$conf讀取
221 then
222 subpat=‘^[^=]*basedir[^=]*=\(.*\)$‘
223 dirs=`sed -e "/$subpat/!d" -e ‘s//\1/‘ $conf`
224 for d in $dirs
225 do
226 d=`echo $d | sed -e ‘s/[ ]//g‘`
227 if test -x "$d/bin/my_print_defaults"
228 then
229 print_defaults="$d/bin/my_print_defaults"
230 break
231 fi
232 if test -x "$d/bin/mysql_print_defaults"
233 then
234 print_defaults="$d/bin/mysql_print_defaults"
235 break
236 fi
237 done
238 fi
239
240 # Hope it‘s in the PATH ... but I doubt it
241 test -z "$print_defaults" && print_defaults="my_print_defaults" #還是不行，就用my_print_defaults
242 fi
243
244 #
245 # Read defaults file from ‘basedir‘. If there is no defaults file there
246 # check if it‘s in the old (depricated) place (datadir) and read it from there
247 #
248
249 #配置文件的目錄，先從basedir讀取，不行再讀取datadir的
250 extra_args=""
251 if test -r "$basedir/my.cnf"
252 then
253 extra_args="-e $basedir/my.cnf"
254 else
255 if test -r "$datadir/my.cnf"
256 then
257 extra_args="-e $datadir/my.cnf"
258 fi
259 fi
260
261 #使用parse_server_arguments函數和my_print_defaults 從my.cnf 中獲取相應的參數並付給相應的變量
262 parse_server_arguments `$print_defaults $extra_args mysqld server mysql_server mysql.server`
263
264 #
265 # Set pid file if not given
266 #指定mysql啓動時進程文件的位置
267 if test -z "$mysqld_pid_file_path"
268 then
269 mysqld_pid_file_path=$datadir/`hostname`.pid
270 else
271 case "$mysqld_pid_file_path" in
272 /* ) ;;
273 * ) mysqld_pid_file_path="$datadir/$mysqld_pid_file_path" ;;
274 esac
275 fi
276
277 case "$mode" in
278 ‘start‘)
279 # Start daemon
280
281 # Safeguard (relative paths, core dumps..)
282 cd $basedir
283
284 echo $echo_n "Starting MySQL"
285 if test -x $bindir/mysqld_safe #如果mysqld_safe存在且可執行
286 then
287 # Give extra arguments to mysqld with the my.cnf file. This script
288 # may be overwritten at next upgrade.
289 #關鍵語句，啓動mysqld_safe，傳入3個參數：datadir,pid-file,other_args；將輸出丟棄到系統黑洞/dev/null
290 $bindir/mysqld_safe --datadir="$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鎖的檢測和創建
294 if test -w "$lockdir" #如果存在且可寫
295 then
296 touch "$lock_file_path"
297 fi
298
299 exit $return_value
300 else
301 log_failure_msg "Couldn‘t find MySQL server ($bindir/mysqld_safe)"
302 fi
303 ;;
304
305 ‘stop‘)
306 # Stop daemon. We use a signal here to avoid having to know the
307 # root password.
308
309 if test -s "$mysqld_pid_file_path" #如果非空
310 then
311 mysqld_pid=`cat "$mysqld_pid_file_path"` ＃獲取mysqld進程
312
313 if (kill -0 $mysqld_pid 2>/dev/null)
314 then
315 echo $echo_n "Shutting down MySQL"
316 kill $mysqld_pid ＃殺死
317 # mysqld should remove the pid file when it exits, so wait for it.
318 wait_for_pid removed "$mysqld_pid" "$mysqld_pid_file_path"; return_value=$?
319 else
320 log_failure_msg "MySQL server process #$mysqld_pid is not running!"
321 rm "$mysqld_pid_file_path"
322 fi
323
324 # Delete lock for RedHat / SuSE
325 if test -f "$lock_file_path" #如果存在鎖，需要移除
326 then
327 rm -f "$lock_file_path"
328 fi
329 exit $return_value
330 else
331 log_failure_msg "MySQL server PID file could not be found!"
332 fi
333 ;;
334
335 ‘restart‘)
336 # Stop the service and regardless of whether it was #重啓mysql
337 # running or not, start it again.
338 if $0 stop $other_args; then
339 $0 start $other_args
340 else
341 log_failure_msg "Failed to stop running server, so refusing to try to start."
342 exit 1
343 fi
344 ;;
345
346 ‘reload‘|‘force-reload‘) #重載mysql
347 if test -s "$mysqld_pid_file_path" ; then
348 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 else
352 log_failure_msg "MySQL PID file could not be found!"
353 exit 1
354 fi
355 ;;
356 ‘status‘)
357 # First, check to see if pid file exists #mysql的狀態
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 0
363 else
364 log_failure_msg "MySQL is not running, but PID file exists"
365 exit 1
366 fi
367 else
368 # Try to find appropriate mysqld process
369 mysqld_pid=`pidof $libexecdir/mysqld`
370
371 # test if multiple pids exist
372 pid_count=`echo $mysqld_pid | wc -w`
373 if test $pid_count -gt 1 ; then
374 log_failure_msg "Multiple MySQL running but PID file could not be found ($mysqld_pid)"
375 exit 5
376 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 2
380 fi
381 log_failure_msg "MySQL is not running"
382 exit 3
383 else
384 log_failure_msg "MySQL is running but PID file could not be found"
385 exit 4
386 fi
387 fi
388 ;;
389 *)
390 # usage #輸出用法的提示
391 basename=`basename "$0"`
392 echo "Usage: $basename {start|stop|restart|reload|force-reload|status} [ MySQL server options ]"
393 exit 1
394 ;;
395 esac
396
397 exit 0