Mysql 5.7 Could not create unix socket lock file

Question

I am trying to create multiple instances of MySQL 5.7 in the same Ubuntu 16.10 32-bit box. I have copied the original data dir to the new one. Created separate log folder for the new instance(the logs are working). Changed the owner to mysql:mysql for the new data dir /var/lib/mysql2 and log dir /var/log/mysql2/. I have removed app-armor. I have posted this Question only after going through the other SO answers...none of which address the multiple instance issue.

Here is my my2.cnf:

[mysqld]
#
# * Basic Settings
#
user            = mysql
pid-file        = /var/run/mysqld/mysqld2.pid
socket          = /var/run/mysqld/mysqld2.sock
port            = 3307
basedir         = /usr
datadir         = /var/lib/mysql2
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_size         = 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-options  = BACKUP
#max_connections        = 100
#table_open_cache       = 64
#thread_concurrency     = 10
#
# * Query Cache Configuration
#
query_cache_limit       = 1M
query_cache_size        = 16M

[mysqld_safe]
socket          = /var/run/mysqld/mysqld2.sock
nice            = 0

As you can see I have changed the port to 3307 and others respectively. Now when I run (have to add the sudo to mysqld):

sudo mysqld --defaults-file=/etc/mysql/my2.cnf &

I receive:

2017-03-22T08:31:21.684121Z 0 [Note] mysqld (mysqld 5.7.17-0ubuntu0.16.10.1) starting as process 13676 ...
2017-03-22T08:31:21.687115Z 0 [Note] InnoDB: PUNCH HOLE support available
2017-03-22T08:31:21.687131Z 0 [Note] InnoDB: Mutexes and rw_locks use GCC atomic builtins
2017-03-22T08:31:21.687135Z 0 [Note] InnoDB: Uses event mutexes
2017-03-22T08:31:21.687140Z 0 [Note] InnoDB: GCC builtin __atomic_thread_fence() is used for memory barrier
2017-03-22T08:31:21.687143Z 0 [Note] InnoDB: Compressed tables use zlib 1.2.8
2017-03-22T08:31:21.687147Z 0 [Note] InnoDB: Using Linux native AIO
2017-03-22T08:31:21.687281Z 0 [Note] InnoDB: Number of pools: 1
2017-03-22T08:31:21.687344Z 0 [Note] InnoDB: Not using CPU crc32 instructions
2017-03-22T08:31:21.688116Z 0 [Note] InnoDB: Initializing buffer pool, total size = 128M, instances = 1, chunk size = 128M
2017-03-22T08:31:21.693801Z 0 [Note] InnoDB: Completed initialization of buffer pool
2017-03-22T08:31:21.694846Z 0 [Note] InnoDB: If the mysqld execution user is authorized, page cleaner thread priority can be changed. See the $
2017-03-22T08:31:21.708807Z 0 [Note] InnoDB: Highest supported file format is Barracuda.
2017-03-22T08:31:21.776053Z 0 [Note] InnoDB: Creating shared tablespace for temporary tables
2017-03-22T08:31:21.776228Z 0 [Note] InnoDB: Setting file './ibtmp1' size to 12 MB. Physically writing the file full; Please wait ...
2017-03-22T08:31:21.825266Z 0 [Note] InnoDB: File './ibtmp1' size is now 12 MB.
2017-03-22T08:31:21.826338Z 0 [Note] InnoDB: 96 redo rollback segment(s) found. 96 redo rollback segment(s) are active.
2017-03-22T08:31:21.826359Z 0 [Note] InnoDB: 32 non-redo rollback segment(s) are active.
2017-03-22T08:31:21.826695Z 0 [Note] InnoDB: Waiting for purge to start
2017-03-22T08:31:21.880277Z 0 [Note] InnoDB: 5.7.17 started; log sequence number 2535531
2017-03-22T08:31:21.881286Z 0 [Note] InnoDB: Loading buffer pool(s) from /var/lib/mysql2/ib_buffer_pool
2017-03-22T08:31:21.881581Z 0 [Note] Plugin 'FEDERATED' is disabled.
2017-03-22T08:31:21.887687Z 0 [Note] InnoDB: Buffer pool(s) load completed at 170322 14:01:21
2017-03-22T08:31:21.890330Z 0 [Warning] Failed to set up SSL because of the following SSL library error: SSL context is not usable without cer$
2017-03-22T08:31:21.890380Z 0 [Note] Server hostname (bind-address): '127.0.0.1'; port: 3307
2017-03-22T08:31:21.890407Z 0 [Note]   - '127.0.0.1' resolves to '127.0.0.1';
2017-03-22T08:31:21.890695Z 0 [Note] Server socket created on IP: '127.0.0.1'.
2017-03-22T08:31:21.890791Z 0 [ERROR] Could not create unix socket lock file /var/run/mysqld/mysqld2.sock.lock.
2017-03-22T08:31:21.890807Z 0 [ERROR] Unable to setup unix socket lock file.
2017-03-22T08:31:21.890819Z 0 [ERROR] Aborting

What am I missing?

...and has permissions like `rwx...` and the socket file doesn't already exist with wrong permissions or ownership? — Michael - sqlbot, Mar 22 '17 at 17:38
The original .sock file has no executable permisions(rw). Also I cannot see the mysql2.sock in the folder. — Mallik Kumar, Mar 22 '17 at 19:11
If it were me, I'd start mysqld under `strace` to see exactly what call is being made and what error is returned. This will produce a lot of output, but it shouldn't be unmanageable since mysqld is shutting down. — Michael - sqlbot, Mar 22 '17 at 20:04

score 1 · Answer 1 · answered Jun 09 '20 at 09:18

For those who are using apparmor the following permissions in /etc/apparmor.d/usr.sbin.mysqld allowed mysqld to create and use the lock file.

/var/run/mysqld/mysqld2.pid rw,
/var/run/mysqld/mysqld2.sock rw,
/var/run/mysqld/mysqld2.sock.lock rw,

Then run the following as root to reload the profile.

apparmor_parser -r /etc/apparmor.d/usr.sbin.mysqld

For some reason i got OP's error without rw permissions on all three of these files.

score 1 · Answer 2 · answered Jul 08 '21 at 00:05

check whether there is a lock file

ls /var/run/mysqld/mysqld2.sock.lock

1. if exists

1.1 check which process use the lock file

lsof /var/run/mysqld/mysqld2.sock.lock

1.1.1 if there is not a process using the lock file

rm lock file

rm /var/run/mysqld/mysqld2.sock.lock

and then start mysql

1.1.2 if there is a process using the lock file

change lock file and socket file to another path

2. if not exists

need more information to check what is happing

strace -ff mysqld --defaults-file=/etc/mysql/my2.cnf