Mysql 5.7 Could not create unix socket lock file - mysql

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?

Answer 1

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

Answer 2

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.