Mysql won't start anymore [closed]

Question

I wanted to check out my logserver again, but all of sudden i get this message when i visit the url:

I am running on ubuntu xenial

FATAL: Cannot connect to MySQL server on 'localhost'. Please make sure you have specified a valid MySQL database name in 'include/config.php'

when i do journalctl -xe i get the following message:

-- Unit mysql.service has begun starting up.
Jun 15 19:26:12 arjanlog audit[3665]: AVC apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" name="/proc/3665/status" pid=3665 comm="mysqld" requested_mask="r" denied_mask="r" fsuid=112 ouid=112

Jun 15 19:26:12 arjanlog audit[3665]: AVC apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" name="/sys/devices/system/node/" pid=3665 comm="mysqld" requested_mask="r" denied_mask="r" fsuid=112 ouid=0

Jun 15 19:26:12 arjanlog audit[3665]: AVC apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" name="/proc/3665/status" pid=3665 comm="mysqld" requested_mask="r" denied_mask="r" fsuid=112 ouid=112
Jun 15 19:26:12 arjanlog kernel: audit: type=1400 audit(1497547572.504:69): apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" 
name="/proc/3665/status" pid=3665 comm="mysqld" requested_mask="r" denied_m

Jun 15 19:26:12 arjanlog kernel: audit: type=1400 audit(1497547572.504:70): apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" name="/sys/devices/system/node/" pid=3665 comm="mysqld" requested_mask="r"

Jun 15 19:26:12 arjanlog kernel: audit: type=1400 audit(1497547572.504:71): apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" name="/proc/3665/status" pid=3665 comm="mysqld" requested_mask="r" denied_m

Jun 15 19:26:12 arjanlog systemd[1]: mysql.service: Main process exited, code=exited, status=1/FAILURE

Answer 1

I had this problem too and solved it by fixing the apparmor configuration file at /etc/apparmor.d/usr.sbin.mysqld. I added these lines:

  /proc/*/status r,
  /sys/devices/system/node/ r,
  /sys/devices/system/node/node0/meminfo r,

Your journalctl -xe output shows the files MySQL needs permission to use. You can also look in /var/log/syslog:

Jun 15 19:26:12 arjanlog audit[3665]: AVC apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" name="/proc/3665/status" pid=3665 comm="mysqld" requested_mask="r" denied_mask="r" fsuid=112 ouid=112
Jun 15 19:26:12 arjanlog audit[3665]: AVC apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" name="/sys/devices/system/node/" pid=3665 comm="mysqld" requested_mask="r" denied_mask="r" fsuid=112 ouid=0
Jun 15 19:26:12 arjanlog audit[3665]: AVC apparmor="DENIED" operation="open" profile="/usr/sbin/mysqld" name="/proc/3665/status" pid=3665 comm="mysqld" requested_mask="r" denied_mask="r" fsuid=112 ouid=112

That means that /usr/sbin/mysqld was DENIED trying to open /proc/3665/status and /sys/devices/system/node/ for reading (r).

Note that in the apparmor config file the trailing slash in /sys/devices/system/node/ is necessary, so don't leave it off!