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？
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/
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。