之前在系统上装了个MySQL用于测试，今天发现启动mysqld_safe进程的时候报错,如下所示：
[root@bak local]# mysqld_safe &
[1] 2631
[root@bak local]# Starting mysqld daemon with databases from /data/mysql/mysql_3306/data
STOPPING server from pid file /data/mysql/mysql_3306/data/bak.pid
141017 09:20:23 mysqld ended
[1]+ Done mysqld_safe
由于我的my.cnf并没有改名，使用的是默认的/etc/my.cnf这个位置，因此mysqld_safe &可以不用指定任何参数，需要的参数已经在my.cnf中指定了，如果使用的my.cnf位置不在/etc/下面，或者改过了自定义的名字，那么需要用--defaults-file参数来指定my.cnf文件的位置
[root@bak local]# cd /data/mysql/mysql_3306/logs/
[root@bak logs]# ll
total 0
查看日志，并没有任何binlog生成，这里说明一下，这个环境是从原来的一台主机上clone过来的，clone完以后没有启动过MySQL,我想可能是因为这个缘故
[root@bak mysql_3306]# cd /usr/local
[root@bak local]# chown -R mysql:mysql /data/mysql/
[root@bak local]# chown -R mysql:mysql /usr/local/mysql/
[root@bak local]# ll
total 76
drwxr-xr-x 2 mysql 502 4096 Aug 25 11:39 bin
-rw-rw---- 1 mysql root 432 Oct 17 09:20 error.log
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 etc
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 games
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 include
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 lib
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 libexec
lrwxrwxrwx 1 root root 38 Sep 24 00:12 mysql -> /opt/mysql/mysql-5.5.39-linux2.6-i686/
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 sbin
drwxr-xr-x 5 mysql 502 4096 Aug 25 11:39 share
drwxr-xr-x 2 mysql 502 4096 Sep 23 20:34 src
[root@bak local]# id mysql
uid=501(mysql) gid=1000(mysql) groups=1000(mysql)
mysql用户id为501，但不知为何显示的是mysql 502的形式，而不是mysql mysql
开始以为是因为/usr/local/mysql这个目录是root:root的缘故，但改为mysql:mysql后，依然无法启动
[root@bak data]# chown -R mysql:mysql /usr/local
[root@bak data]# cd /usr/local
[root@bak local]# ll
total 76
drwxr-xr-x 2 mysql 502 4096 Aug 25 11:39 bin
-rw-rw---- 1 mysql root 432 Oct 17 09:20 error.log
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 etc
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 games
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 include
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 lib
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 libexec
lrwxrwxrwx 1 mysql mysql 38 Sep 24 00:12 mysql -> /opt/mysql/mysql-5.5.39-linux2.6-i686/
drwxr-xr-x 2 mysql 502 4096 Aug 8 2008 sbin
drwxr-xr-x 5 mysql 502 4096 Aug 25 11:39 share
drwxr-xr-x 2 mysql 502 4096 Sep 23 20:34 src
[root@bak local]# mysqld_safe &
[1] 2692
[root@bak local]# Starting mysqld daemon with databases from /data/mysql/mysql_3306/data
[root@bak local]# mysql
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
报了一个无法通过socket连接到服务器，于是想是不是应该在client项目中添加socket=/tmp/mysql.sock这个参数
--先查看下原来有的配置
[root@bak local]# cat /etc/my.cnf
[client]
port = 3306
socket = /tmp/mysql.sock
[mysqld_safe]
open_files_limit = 8192
user = mysql
log-error = error.log
...省略以下部分
看来client总已经指定了socket，应该不是这个问题，要判断问题出在哪里，最直接都就是查看error.log文件，由于我在my.cnf参数中指定了error.log的位置，放在了数据文件目录下，并更改了名字。如果没有改，默认的名字为
[root@bak local]# cat /data/mysql/mysql_3306/data/error.log
141017 9:24:53 [Warning] Using unique option prefix myisam_recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use
the full name instead.
141017 9:24:53 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: Table 'mysql.plugin' doesn't exist
141017 9:24:53 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
141017 9:24:53 InnoDB: The InnoDB memory heap is disabled
141017 9:24:53 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
141017 9:24:53 InnoDB: Compressed tables use zlib 1.2.3
141017 9:24:53 InnoDB: Using Linux native AIO
141017 9:24:53 InnoDB: Initializing buffer pool, size = 128.0M
141017 9:24:53 InnoDB: Completed initialization of buffer pool
InnoDB: The first specified data file ./ibdata1 did not exist:
InnoDB: a new database to be created!
141017 9:24:53 InnoDB: Setting file ./ibdata1 size to 100 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB: 100
141017 9:24:58 InnoDB: Log file ./ib_logfile0 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile0 size to 100 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB: 100
141017 9:25:03 InnoDB: Log file ./ib_logfile1 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile1 size to 100 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB: 100
141017 9:25:08 InnoDB: Log file ./ib_logfile2 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile2 size to 100 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB: 100
InnoDB: Doublewrite buffer not found: creating new
InnoDB: Doublewrite buffer created
InnoDB: 127 rollback segment(s) active.
InnoDB: Creating foreign key constraint system tables
InnoDB: Foreign key constraint system tables created
141017 9:25:13 InnoDB: Waiting for the background threads to start
141017 9:25:14 InnoDB: 5.5.39 started; log sequence number 0
141017 9:25:14 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306
141017 9:25:14 [Note] - '0.0.0.0' resolves to '0.0.0.0';
141017 9:25:14 [Note] Server socket created on IP: '0.0.0.0'.
141017 9:25:14 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
141017 9:26:15 [Warning] Using unique option prefix myisam_recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
141017 9:26:15 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: Table 'mysql.plugin' doesn't exist
141017 9:26:15 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
141017 9:26:15 InnoDB: The InnoDB memory heap is disabled
141017 9:26:15 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
141017 9:26:15 InnoDB: Compressed tables use zlib 1.2.3
141017 9:26:15 InnoDB: Using Linux native AIO
141017 9:26:15 InnoDB: Initializing buffer pool, size = 128.0M
141017 9:26:15 InnoDB: Completed initialization of buffer pool
141017 9:26:15 InnoDB: highest supported file format is Barracuda.
InnoDB: Log scan progressed past the checkpoint lsn 48941
141017 9:26:15 InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Restoring possible half-written data pages from the doublewrite
InnoDB: buffer...
InnoDB: Doing recovery: scanned up to log sequence number 1595668
141017 9:26:15 InnoDB: Starting an apply batch of log records to the database...
InnoDB: Progress in percents: 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72
73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
InnoDB: Apply batch completed
141017 9:26:15 InnoDB: Waiting for the background threads to start
141017 9:26:16 InnoDB: 5.5.39 started; log sequence number 1595668
141017 9:26:16 [Note] Recovering after a crash using /data/mysql/mysql_3306/logs/mysql-bin
141017 9:26:16 [Note] Starting crash recovery...
141017 9:26:16 [Note] Crash recovery finished.
141017 9:26:17 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306
141017 9:26:17 [Note] - '0.0.0.0' resolves to '0.0.0.0';
141017 9:26:17 [Note] Server socket created on IP: '0.0.0.0'.
141017 9:26:17 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
日志中报错提示无法打开mysql.plugin表，也不存在mysql.host这张表，由于是测试环境，没有什么数据，于是决定重新初始化MySQL
[root@bak local]# cd mysql
[root@bak mysql]# ./scripts/mysql_install_db
Installing MySQL system tables...
141017 9:28:24 [Warning] options --log-slow-admin-statements, --log-queries-not-using-indexes and --log-slow-slave-statements have no effect if --log_slow_queries is not set
OK
Filling help tables...
141017 9:28:25 [Warning] options --log-slow-admin-statements, --log-queries-not-using-indexes and --log-slow-slave-statements have no effect if --log_slow_queries is not set
OK
To start mysqld at boot time you have to copy
support-files/mysql.server to the right place for your system
PLEASE REMEMBER TO SET A PASSWORD FOR THE MySQL root USER !
To do so, start the server, then issue the following commands:
/usr/local/mysql/bin/mysqladmin -u root password 'new-password'
/usr/local/mysql/bin/mysqladmin -u root -h bak password 'new-password'
Alternatively you can run:
/usr/local/mysql/bin/mysql_secure_installation
which will also give you the option of removing the test
databases and anonymous user created by default. This is
strongly recommended for production servers.
See the manual for more instructions.
You can start the MySQL daemon with:
cd /usr/local/mysql ; /usr/local/mysql/bin/mysqld_safe &
You can test the MySQL daemon with mysql-test-run.pl
cd /usr/local/mysql/mysql-test ; perl mysql-test-run.pl
Please report any problems at http://bugs.mysql.com/
[root@bak mysql]# mysqld_safe &
[1] 2858
[root@bak mysql]# Starting mysqld daemon with databases from /data/mysql/mysql_3306/data
[root@bak mysql]# mysqSTOPPING server from pid file /data/mysql/mysql_3306/data/bak.pid
l141017 09:28:36 mysqld ended
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
[1]+ Done mysqld_safe
初始化时成功的，可以看到有2个OK，不过启动依然报错，再次查看error.log
[root@bak mysql]# cat /data/mysql/mysql_3306/data/error.log
141017 9:24:53 [Warning] Using unique option prefix myisam_recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
141017 9:24:53 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: Table 'mysql.plugin' doesn't exist
141017 9:24:53 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
141017 9:24:53 InnoDB: The InnoDB memory heap is disabled
141017 9:24:53 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
141017 9:24:53 InnoDB: Compressed tables use zlib 1.2.3
141017 9:24:53 InnoDB: Using Linux native AIO
141017 9:24:53 InnoDB: Initializing buffer pool, size = 128.0M
141017 9:24:53 InnoDB: Completed initialization of buffer pool
InnoDB: The first specified data file ./ibdata1 did not exist:
InnoDB: a new database to be created!
141017 9:24:53 InnoDB: Setting file ./ibdata1 size to 100 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB: 100
141017 9:24:58 InnoDB: Log file ./ib_logfile0 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile0 size to 100 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB: 100
141017 9:25:03 InnoDB: Log file ./ib_logfile1 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile1 size to 100 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB: 100
141017 9:25:08 InnoDB: Log file ./ib_logfile2 did not exist: new to be created
InnoDB: Setting log file ./ib_logfile2 size to 100 MB
InnoDB: Database physically writes the file full: wait...
InnoDB: Progress in MB: 100
InnoDB: Doublewrite buffer not found: creating new
InnoDB: Doublewrite buffer created
InnoDB: 127 rollback segment(s) active.
InnoDB: Creating foreign key constraint system tables
InnoDB: Foreign key constraint system tables created
141017 9:25:13 InnoDB: Waiting for the background threads to start
141017 9:25:14 InnoDB: 5.5.39 started; log sequence number 0
141017 9:25:14 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306
141017 9:25:14 [Note] - '0.0.0.0' resolves to '0.0.0.0';
141017 9:25:14 [Note] Server socket created on IP: '0.0.0.0'.
141017 9:25:14 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
141017 9:26:15 [Warning] Using unique option prefix myisam_recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
141017 9:26:15 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: Table 'mysql.plugin' doesn't exist
141017 9:26:15 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
141017 9:26:15 InnoDB: The InnoDB memory heap is disabled
141017 9:26:15 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
141017 9:26:15 InnoDB: Compressed tables use zlib 1.2.3
141017 9:26:15 InnoDB: Using Linux native AIO
141017 9:26:15 InnoDB: Initializing buffer pool, size = 128.0M
141017 9:26:15 InnoDB: Completed initialization of buffer pool
141017 9:26:15 InnoDB: highest supported file format is Barracuda.
InnoDB: Log scan progressed past the checkpoint lsn 48941
141017 9:26:15 InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Restoring possible half-written data pages from the doublewrite
InnoDB: buffer...
InnoDB: Doing recovery: scanned up to log sequence number 1595668
141017 9:26:15 InnoDB: Starting an apply batch of log records to the database...
InnoDB: Progress in percents: 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72
73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99
InnoDB: Apply batch completed
141017 9:26:15 InnoDB: Waiting for the background threads to start
141017 9:26:16 InnoDB: 5.5.39 started; log sequence number 1595668
141017 9:26:16 [Note] Recovering after a crash using /data/mysql/mysql_3306/logs/mysql-bin
141017 9:26:16 [Note] Starting crash recovery...
141017 9:26:16 [Note] Crash recovery finished.
141017 9:26:17 [Note] Server hostname (bind-address): '0.0.0.0'; port: 3306
141017 9:26:17 [Note] - '0.0.0.0' resolves to '0.0.0.0';
141017 9:26:17 [Note] Server socket created on IP: '0.0.0.0'.
141017 9:26:17 [ERROR] Fatal error: Can't open and lock privilege tables: Table 'mysql.host' doesn't exist
141017 9:28:34 [Warning] Using unique option prefix myisam_recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
141017 9:28:34 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)
141017 9:28:34 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
141017 9:28:34 InnoDB: The InnoDB memory heap is disabled
141017 9:28:34 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
141017 9:28:34 InnoDB: Compressed tables use zlib 1.2.3
141017 9:28:34 InnoDB: Using Linux native AIO
141017 9:28:34 InnoDB: Initializing buffer pool, size = 128.0M
141017 9:28:34 InnoDB: Completed initialization of buffer pool
141017 9:28:34 InnoDB: highest supported file format is Barracuda.
InnoDB: The log sequence number in ibdata files does not match
InnoDB: the log sequence number in the ib_logfiles!
141017 9:28:34 InnoDB: Database was not shut down normally!
InnoDB: Starting crash recovery.
InnoDB: Reading tablespace information from the .ibd files...
InnoDB: Restoring possible half-written data pages from the doublewrite
InnoDB: buffer...
141017 9:28:34 InnoDB: Waiting for the background threads to start
141017 9:28:35 InnoDB: 5.5.39 started; log sequence number 1595668
/usr/libexec/mysqld: File '/data/mysql/mysql_3306/logs/mysql-bin.000004' not found (Errcode: 13)
141017 9:28:35 [ERROR] Failed to open log (file '/data/mysql/mysql_3306/logs/mysql-bin.000004', errno 13)
141017 9:28:35 [ERROR] Could not open log file
141017 9:28:35 [ERROR] Can't init tc log
141017 9:28:35 [ERROR] Aborting
141017 9:28:35 InnoDB: Starting shutdown...
141017 9:28:36 InnoDB: Shutdown completed; log sequence number 1595668
141017 9:28:36 [Note] /usr/libexec/mysqld: Shutdown complete
141017 9:30:32 [Warning] Using unique option prefix myisam_recover instead of myisam-recover-options is deprecated and will be removed in a future release. Please use the full name instead.
141017 9:30:32 [Note] Plugin 'FEDERATED' is disabled.
/usr/libexec/mysqld: Can't find file: './mysql/plugin.frm' (errno: 13)
141017 9:30:32 [ERROR] Can't open the mysql.plugin table. Please run mysql_upgrade to create it.
141017 9:30:32 InnoDB: The InnoDB memory heap is disabled
141017 9:30:32 InnoDB: Mutexes and rw_locks use InnoDB's own implementation
141017 9:30:32 InnoDB: Compressed tables use zlib 1.2.3
141017 9:30:32 InnoDB: Using Linux native AIO
141017 9:30:32 InnoDB: Initializing buffer pool, size = 128.0M
141017 9:30:32 InnoDB: Completed initialization of buffer pool
141017 9:30:32 InnoDB: highest supported file format is Barracuda.
141017 9:30:32 InnoDB: Waiting for the background threads to start
141017 9:30:33 InnoDB: 5.5.39 started; log sequence number 1595668
/usr/libexec/mysqld: File '/data/mysql/mysql_3306/logs/mysql-bin.000004' not found (Errcode: 13)
141017 9:30:33 [ERROR] Failed to open log (file '/data/mysql/mysql_3306/logs/mysql-bin.000004', errno 13)
141017 9:30:33 [ERROR] Could not open log file
141017 9:30:33 [ERROR] Can't init tc log
141017 9:30:33 [ERROR] Aborting
141017 9:30:33 InnoDB: Starting shutdown...
141017 9:30:34 InnoDB: Shutdown completed; log sequence number 1595668
141017 9:30:34 [Note] /usr/libexec/mysqld: Shutdown complete
现在error.log里很明显地指出errno为13，我们知道13就是权限问题，这个可以perror命令查看
[root@bak mysql]# perror 13
OS error code 13: Permission denied
位置可以通过which来定位
[root@bak mysql]# which perror
/usr/bin/perror
或者用find定位也是可以的
[root@bak mysql]#
find / -name perror -print
/opt/mysql/mysql-5.5.39-linux2.6-i686/bin/perror
/usr/bin/perror
既然找到了无法启动的真正原因，那么对症下药，把权限问题解决，问题就可以搞定了
[root@bak mysql]# cd /data/mysql/mysql_3306/data
[root@bak data]# ll
total 410036
-rw-rw---- 1 mysql mysql 7950 Oct 17 09:30 error.log
-rw-rw---- 1 mysql mysql 104857600 Oct 17 09:30 ibdata1
-rw-rw---- 1 mysql mysql 104857600 Oct 17 09:30 ib_logfile0
-rw-rw---- 1 mysql mysql 104857600 Oct 17 09:25 ib_logfile1
-rw-rw---- 1 mysql mysql 104857600 Oct 17 09:25 ib_logfile2
drwx------ 2 root root 4096 Oct 17 09:28 mysql
drwx------ 2 root root 4096 Oct 17 09:28 performance_schema
drwx------ 2 root root 4096 Oct 17 09:28 test
[root@bak data]# chown -R mysql:mysql ./
[root@bak data]# ll
total 410036
-rw-rw---- 1 mysql mysql 7950 Oct 17 09:30 error.log
-rw-rw---- 1 mysql mysql 104857600 Oct 17 09:30 ibdata1
-rw-rw---- 1 mysql mysql 104857600 Oct 17 09:30 ib_logfile0
-rw-rw---- 1 mysql mysql 104857600 Oct 17 09:25 ib_logfile1
-rw-rw---- 1 mysql mysql 104857600 Oct 17 09:25 ib_logfile2
drwx------ 2 mysql mysql 4096 Oct 17 09:28 mysql
drwx------ 2 mysql mysql 4096 Oct 17 09:28 performance_schema
drwx------ 2 mysql mysql 4096 Oct 17 09:28 test
开始还去调整了/data/mysql/mysql_3306/data目录下面几个数据库的权限，但发现依然无法启动，看来不是这几个目录的权限问题
[root@bak data]# mysqld_safe &
[1] 2988
[root@bak data]# Starting mysqld daemon with databases from /data/mysql/mysql_3306/data
[root@bak data]# mysqlSTOPPING server from pid file /data/mysql/mysql_3306/data/bak.pid
141017 09:32:08 mysqld ended
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/tmp/mysql.sock' (2)
[1]+ Done mysqld_safe
error.log日志内容和之前一样，仍然报errno 13，就不贴了。针对之前给出的error.log日志里提示的对mysql-bin.000004读写权限的问题做一下处理
[root@bak mysql]# cd /data/mysql/mysql_3306/logs
[root@bak logs]# ll
total 1092
-rw-rw---- 1 mysql mysql 107 Oct 17 09:25 mysql-bin.000001
-rw-rw---- 1 mysql mysql 107 Oct 17 09:26 mysql-bin.000002
-rw-rw---- 1 root root 27681 Oct 17 09:28 mysql-bin.000003
-rw-rw---- 1 root root 1070549 Oct 17 09:28 mysql-bin.000004
-rw-rw---- 1 mysql mysql 180 Oct 17 09:28 mysql-bin.index
[root@bak logs]# chown -R mysql:mysql ./
[root@bak logs]# ll
total 1092
-rw-rw---- 1 mysql mysql 107 Oct 17 09:25 mysql-bin.000001
-rw-rw---- 1 mysql mysql 107 Oct 17 09:26 mysql-bin.000002
-rw-rw---- 1 mysql mysql 27681 Oct 17 09:28 mysql-bin.000003
-rw-rw---- 1 mysql mysql 1070549 Oct 17 09:28 mysql-bin.000004
-rw-rw---- 1 mysql mysql 180 Oct 17 09:28 mysql-bin.index
原来是root root权限，改为mysql mysql了，再次启动MySQL进程
[root@bak logs]# ps -ef|grep mysql
root 3060 2591 0 09:35 pts/0 00:00:00 grep mysql
[root@bak logs]# mysqld_safe &
[1] 3061
[root@bak logs]# Starting mysqld daemon with databases from /data/mysql/mysql_3306/data
[root@bak logs]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.39-log MySQL Community Server (GPL)
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
(testing)root@localhost [(none)]> exit
[root@bak logs]# ps aux | grep -v grep | grep mysql
root 3061 0.0 0.1 4484 1152 pts/0 S 09:35 0:00 /bin/sh /usr/bin/mysqld_safe
mysql 3095 0.0 3.1 330320 32216 pts/0 Sl 09:35 0:02 /usr/libexec/mysqld --basedir=/usr/local/mysql --datadir=/data/mysql/mysql_3306/data --user=mysql
--pid-file=/data/mysql/mysql_3306/data/bak.pid --skip-external-locking --port=3306 --socket=/tmp/mysql.sock
这次，数据库顺利启动了，从mysql进程中可以看到，mysqld_safe实际去调用的还是mysqld
总结：
当我们遭遇数据库无法启动，如：自动终止进程stopping from pid file或是无法通过socket连接到服务器等错误，首先要去查看数据库的error.log日志，其中有详细的提示（各种ERROR和WARNING），来给你提供无法启动的线索，我们要做的就是更具这些线索，来做相应的处理，才能更快、更好地解决问题。
