我有运行 MySQL 服务器 5.5.24 的 Ubuntu 12.04。我可以连接mysql --user root -p。status它显示：
...
Connection: Localhost via UNIX socket
...
当我尝试连接mysql --host 127.0.0.1 --user root -p（或使用--protocol=tcp）时，我可以连接（得到提示），但我尝试做的任何事情都会给我这个错误：
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id: 39
Current database: *** NONE ***
ERROR 2013 (HY000): Lost connection to MySQL server during query
netstat -pal | grep -P '3306|mysql'显示：
tcp 0 0 localhost:mysql *:* LISTEN 26535/mysqld
unix 2 [ ACC ] STREAM LISTENING 121787 26535/mysqld /var/run/mysqld/mysqld.sock
unix 3 [ ] STREAM CONNECTED 18810 2252/mysql-workbenc
unix 3 [ ] STREAM CONNECTED 16377 2252/mysql-workbenc
unix 3 [ ] STREAM CONNECTED 18765 2252/mysql-workbenc
unix 3 [ ] STREAM CONNECTED 17959 2252/mysql-workbenc
使用 UNIX 套接字，我可以正常工作。有什么想法吗？
编辑-我的/etc/mysql/my.cnf
#
# The MySQL database server configuration file.
#
# You can copy this to one of:
# - "/etc/mysql/my.cnf" to set global options,
# - "~/.my.cnf" to set user-specific options.
#
# One can use all long options that the program supports.
# Run program with --help to get a list of available options and with
# --print-defaults to see which it would actually understand and use.
#
# For explanations see
# http://dev.mysql.com/doc/mysql/en/server-system-variables.html
# This will be passed to all mysql clients
# It has been reported that passwords should be enclosed with ticks/quotes
# escpecially if they contain "#" chars...
# Remember to edit /etc/mysql/debian.cnf when changing the socket location.
[client]
port = 3306
socket = /var/run/mysqld/mysqld.sock
# Here is entries for some specific programs
# The following values assume you have at least 32M ram
# This was formally known as [safe_mysqld]. Both versions are currently parsed.
[mysqld_safe]
socket = /var/run/mysqld/mysqld.sock
nice = 0
[mysqld]
#
# * Basic Settings
#
user = mysql
pid-file = /var/run/mysqld/mysqld.pid
socket = /var/run/mysqld/mysqld.sock
port = 3306
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
lc-messages-dir = /usr/share/mysql
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address = 127.0.0.1
#
# * Fine Tuning
#
key_buffer = 16M
max_allowed_packet = 16M
thread_stack = 192K
thread_cache_size = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover = BACKUP
#max_connections = 100
#table_cache = 64
#thread_concurrency = 10
#
# * Query Cache Configuration
#
query_cache_limit = 1M
query_cache_size = 16M
#
# * Logging and Replication
#
# Both location gets rotated by the cronjob.
# Be aware that this log type is a performance killer.
# As of 5.1 you can enable the log at runtime!
#general_log_file = /var/log/mysql/mysql.log
#general_log = 1
#
# Error logging goes to syslog due to /etc/mysql/conf.d/mysqld_safe_syslog.cnf.
#
# Here you can see queries with especially long duration
#log_slow_queries = /var/log/mysql/mysql-slow.log
#long_query_time = 2
#log-queries-not-using-indexes
#
# The following can be used as easy to replay backup logs or for replication.
# note: if you are setting up a replication slave, see README.Debian about
# other settings you may need to change.
#server-id = 1
#log_bin = /var/log/mysql/mysql-bin.log
expire_logs_days = 10
max_binlog_size = 100M
#binlog_do_db = include_database_name
#binlog_ignore_db = include_database_name
#
# * InnoDB
#
# InnoDB is enabled by default with a 10MB datafile in /var/lib/mysql/.
# Read the manual for more InnoDB related options. There are many!
#
# * Security Features
#
# Read the manual, too, if you want chroot!
# chroot = /var/lib/mysql/
#
# For generating SSL certificates I recommend the OpenSSL GUI "tinyca".
#
# ssl-ca=/etc/mysql/cacert.pem
# ssl-cert=/etc/mysql/server-cert.pem
# ssl-key=/etc/mysql/server-key.pem
[mysqldump]
quick
quote-names
max_allowed_packet = 16M
[mysql]
#no-auto-rehash # faster start of mysql but no tab completition
[isamchk]
key_buffer = 16M
#
# * IMPORTANT: Additional settings that can override those from this file!
# The files must end with '.cnf', otherwise they'll be ignored.
#
!includedir /etc/mysql/conf.d/
编辑-新发现
我刚刚发现，每次我尝试使用 tcp 连接并运行某些操作时，mysqld 进程都会崩溃。我看到了它/var/log/syslog并用它ps -ef来验证 PID 是否发生变化：
Oct 24 16:14:47 desktop kernel: [13190.117685] init: mysql main process (27929) terminated with status 1
Oct 24 16:14:47 desktop kernel: [13190.117685] init: mysql main process ended, respawning
Oct 24 16:14:48 desktop kernel: [13190.212097] type=1400 audit(1351088088.044:124): apparmor="STATUS" operation="profile_replace" name="/usr/sbin/mysqld" pid=28079 comm="apparmor_parser"
Oct 24 16:14:50 desktop /etc/mysql/debian-start[28123]: Upgrading MySQL tables if necessary.
Oct 24 16:14:50 desktop /etc/mysql/debian-start[28126]: /usr/bin/mysql_upgrade: the '--basedir' option is always ignored
Oct 24 16:14:50 desktop /etc/mysql/debian-start[28126]: Looking for 'mysql' as: /usr/bin/mysql
Oct 24 16:14:50 desktop /etc/mysql/debian-start[28126]: Looking for 'mysqlcheck' as: /usr/bin/mysqlcheck
Oct 24 16:14:50 desktop /etc/mysql/debian-start[28126]: This installation of MySQL is already upgraded to 5.5.24, use --force if you still need to run mysql_upgrade
Oct 24 16:14:50 desktop /etc/mysql/debian-start[28137]: Checking for insecure root accounts.
Oct 24 16:14:50 desktop /etc/mysql/debian-start[28142]: Triggering myisam-recover for all MyISAM tables
这很像我启动 mysqld 时的常规日志，但我还是发布了它，以防有人从中获得一些有趣的东西。
编辑：我的 /etc/apparmor.d/usr.sbin.mysqld
# vim:syntax=apparmor
# Last Modified: Tue Jun 19 17:37:30 2007
#include <tunables/global>
/usr/sbin/mysqld {
#include <abstractions/base>
#include <abstractions/nameservice>
#include <abstractions/user-tmp>
#include <abstractions/mysql>
#include <abstractions/winbind>
capability dac_override,
capability sys_resource,
capability setgid,
capability setuid,
network tcp,
/etc/hosts.allow r,
/etc/hosts.deny r,
/etc/mysql/*.pem r,
/etc/mysql/conf.d/ r,
/etc/mysql/conf.d/* r,
/etc/mysql/*.cnf r,
/usr/lib/mysql/plugin/ r,
/usr/lib/mysql/plugin/*.so* mr,
/usr/sbin/mysqld mr,
/usr/share/mysql/** r,
/var/log/mysql.log rw,
/var/log/mysql.err rw,
/var/lib/mysql/ r,
/var/lib/mysql/** rwk,
/var/log/mysql/ r,
/var/log/mysql/* rw,
/var/run/mysqld/mysqld.pid w,
/var/run/mysqld/mysqld.sock w,
/run/mysqld/mysqld.pid w,
/run/mysqld/mysqld.sock w,
/sys/devices/system/cpu/ r,
# Site-specific additions and overrides. See local/README for details.
#include <local/usr.sbin.mysqld>
}
编辑-mysqld 崩溃时的堆栈跟踪
我mysqld从命令行运行，然后从其他控制台连接。当我连接时，服务器立即崩溃，输出如下：
121024 16:59:09 [Note] mysqld: ready for connections.
Version: '5.5.24-0ubuntu0.12.04.1' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu)
14:59:37 UTC - mysqld got signal 8 ;
This could be because you hit a bug. It is also possible that this binary
or one of the libraries it was linked against is corrupt, improperly built,
or misconfigured. This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.
key_buffer_size=16777216
read_buffer_size=131072
max_used_connections=1
max_threads=151
thread_count=1
connection_count=1
It is possible that mysqld could use up to
key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 346679 K bytes of memory
Hope that's ok; if not, decrease some variables in the equation.
Thread pointer: 0x7fd27a8ccb10
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 7fd277befe60 thread_stack 0x30000
mysqld(my_print_stacktrace+0x29)[0x7fd278195459]
mysqld(handle_fatal_signal+0x483)[0x7fd27805b1d3]
/lib/x86_64-linux-gnu/libpthread.so.0(+0xfcb0)[0x7fd276b83cb0]
/usr/share/appfirst/libwrap.so.1.0.1(af_timer_now+0x12f)[0x7fd2777fdc53]
/usr/share/appfirst/libwrap.so.1.0.1(intercept_write+0x259)[0x7fd277801594]
/usr/share/appfirst/libwrap.so.1.0.1(write+0x28)[0x7fd2778016e3]
mysqld(net_real_write+0xaa)[0x7fd277eccfea]
mysqld(net_flush+0x1b)[0x7fd277ecd4cb]
mysqld(_Z11net_send_okP3THDjjyyPKc+0x178)[0x7fd277ed3098]
mysqld(_ZN8Protocol13end_statementEv+0x4c)[0x7fd277ed343c]
mysqld(_Z22thd_prepare_connectionP3THD+0x6a)[0x7fd277feb39a]
mysqld(_Z24do_handle_one_connectionP3THD+0xf8)[0x7fd277feb708]
mysqld(handle_one_connection+0x50)[0x7fd277feb830]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x7e9a)[0x7fd276b7be9a]
/lib/x86_64-linux-gnu/libc.so.6(clone+0x6d)[0x7fd2762accbd]
Trying to get some variables.
Some pointers may be invalid and cause the dump to abort.
Query (0): is an invalid pointer
Connection ID (thread ID): 2
Status: NOT_KILLED
The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains
information that should help you find out what is causing the crash.
它提到了一些有关内存使用量的信息（~350MB），因此了解服务器是虚拟的（Windows 7 机器下的 VBox），具有 5GB RAM（主机上的 8GB 内存）可能很重要。我检查了一下，客户机上有 3.5GB 可用空间。