我一直mysql运行良好，然后我从 5.1 升级到 5.5。现在我认为升级后它仍然运行良好，但我现在怀疑自己无法重新启动它。
我查看了其他类似的问题，但没有一个能解决我的问题。我错误地备份了我的数据库，因此任何涉及重新安装的解决方案都无济于事。
输出/var/log/mysql/error.log：
140816 22:35:52 InnoDB: Shutdown completed; log sequence number 2316910
140816 22:35:52 [Note]
140816 22:35:53 [Note] Plugin 'FEDERATED' is disabled.
140816 22:35:53 InnoDB: The InnoDB memory heap is disabled
140816 22:35:53 InnoDB: Mutexes and rw_locks use GCC atomic builtins
140816 22:35:53 InnoDB: Compressed tables use zlib 1.2.8
140816 22:35:53 InnoDB: Using Linux native AIO
140816 22:35:53 InnoDB: Initializing buffer pool, size = 128.0M
140816 22:35:53 InnoDB: Completed initialization of buffer pool
140816 22:35:53 InnoDB: highest supported file format is Barracuda.
140816 22:35:53 InnoDB: Waiting for the background threads to start
140816 22:35:54 InnoDB: 5.5.38 started; log sequence number 2316910
140816 22:35:54 [ERROR] Aborting
140816 22:35:54 InnoDB: Starting shutdown...
我尝试过几种方式启动它，但都给出了相同的消息（大多数情况下，它只是挂在命令行上，然后默默失败）。运行时sudo /etc/init.d/mysql start，它确实显示：
Starting MySQL database server mysqld [fail]
我不太清楚问题是什么，但看起来后台线程没有启动。有什么想法可以尝试吗？
编辑：从启动后/usr/bin/mysqld_safe -v，我得到以下输出：
140817 11:22:31 mysqld_safe Can't log to error log and syslog at the same time. Remove all --log-error configuration options for --syslog to take effect.
140817 11:22:31 mysqld_safe Logging to '/var/log/mysql/error.log'.
140817 11:22:31 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
/usr/bin/mysqld_safe: 126: /usr/bin/mysqld_safe: cannot create /var/log/mysql/error.log: Permission denied
/usr/bin/mysqld_safe: 1: eval: cannot create /var/log/mysql/error.log: Permission denied
140817 11:22:31 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended
/usr/bin/mysqld_safe: 126: /usr/bin/mysqld_safe: cannot create /var/log/mysql/error.log: Permission denied
（我这样做了chmod -R 755 /var/log/mysql，但仍然出现相同的错误。的所有者/var/log/mysql是mysql）
以超级用户身份运行时，错误如下：
140817 12:01:50 mysqld_safe Can't log to error log and syslog at the same time. Remove all --log-error configuration options for --syslog to take effect.
140817 12:01:50 mysqld_safe Logging to '/var/log/mysql/error.log'.
140817 12:01:50 mysqld_safe Starting mysqld daemon with databases from /var/lib/mysql
140817 12:01:53 mysqld_safe mysqld from pid file /var/run/mysqld/mysqld.pid ended