/usr/sbin/mysql code=exited status 203/EXEC ERROR - mysql

Question

I don't know exactly what I did wrong, but it's likely some 'chown' operation that I did. I was trying to allow the user&group mysql:mysql access to a /media/usb drive, but may have inadvertently changed something else.
When I do sudo systemctl start mysql.service I get an error. Upon examining with sudo systemctl status mysqld, I get the following:
mysql.service - MySQL Community Server
Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
Active: activating (start-post) (Result: exit-code) since Fri 2020-06-19 08:11:01 EDT; 19s ago
Process: 15459 ExecStart=/usr/sbin/mysqld (code=exited, status=203/EXEC)
Process: 15444 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)
Main PID: 15459 (code=exited, status=203/EXEC); : 15460 (mysql-systemd-s)
Tasks: 2
Memory: 2.4M
CPU: 175ms
CGroup: /system.slice/mysql.service
└─control
├─15460 /bin/bash /usr/share/mysql/mysql-systemd-start post
└─15687 sleep 1
Jun 19 08:11:01 apil-dlrig systemd[1]: Starting MySQL Community Server...
Jun 19 08:11:01 apil-dlrig systemd[1]: mysql.service: Main process exited, code=exited, status=203/EXEC
When I check ownership on /var/lib/mysql, I get the following, which seems reasonable. I.e. user mysql has full ownership on this folder.
apil#apil-dlrig:~$ sudo ls -la /var/lib/mysql
total 176212
drwx------ 7 mysql mysql 4096 Jun 19 07:34 .
drwxr-xr-x 79 root root 4096 Oct 30 2019 ..
-rw-r----- 1 mysql mysql 56 Oct 20 2019 auto.cnf
-rw------- 1 mysql mysql 1680 Nov 22 2019 ca-key.pem
-rw-r--r-- 1 mysql mysql 1112 Nov 22 2019 ca.pem
-rw-r--r-- 1 mysql mysql 1112 Nov 22 2019 client-cert.pem
-rw------- 1 mysql mysql 1676 Nov 22 2019 client-key.pem
-rw-r--r-- 1 mysql mysql 0 May 5 06:38 debian-5.7.flag
drwxr-x--- 2 mysql mysql 4096 Jun 6 13:44 foo
-rw-r----- 1 mysql mysql 665 Jun 19 07:34 ib_buffer_pool
-rw-r----- 1 mysql mysql 79691776 Jun 19 07:34 ibdata1
-rw-r----- 1 mysql mysql 50331648 Jun 19 07:34 ib_logfile0
-rw-r----- 1 mysql mysql 50331648 Oct 20 2019 ib_logfile1
-rw-r----- 1 mysql mysql 155 Jun 16 07:23 keyring_backup
drwxr-x--- 2 mysql mysql 4096 May 5 06:38 mysql
-rw-r--r-- 1 mysql mysql 6 May 5 06:38 mysql_upgrade_info
drwxr-x--- 2 mysql mysql 4096 May 5 06:38 performance_schema
-rw------- 1 mysql mysql 1680 Nov 22 2019 private_key.pem
drwxr-x--- 2 mysql mysql 4096 Jun 16 07:25 prod
-rw-r--r-- 1 mysql mysql 452 Nov 22 2019 public_key.pem
-rw-r--r-- 1 mysql mysql 1112 Nov 22 2019 server-cert.pem
-rw------- 1 mysql mysql 1680 Nov 22 2019 server-key.pem
drwxr-x--- 2 mysql mysql 12288 Nov 22 2019 sys
The /etc/systemd/system/multi.user.wants.targets/mysql.service looks as the following. Nothing should've changed here, i.e. it is as default as MySQL comes.
# MySQL systemd service file
[Unit]
Description=MySQL Community Server
After=network.target
[Install]
WantedBy=multi-user.target
[Service]
User=mysql
Group=mysql
PermissionsStartOnly=true
ExecStartPre=/usr/share/mysql/mysql-systemd-start pre
ExecStart=/usr/sbin/mysqld
ExecStartPost=/usr/share/mysql/mysql-systemd-start post
TimeoutSec=600
Restart=on-failure
RuntimeDirectory=mysqld
RuntimeDirectoryMode=755
Wondering what could be going wrong. Any help would be appreciated.
Thanks

Answer 1

If you look at the original error, the issue is: ExecStart=/usr/sbin/mysqld (code=exited, status=203/EXEC). Looks like some kind of execution privilege for the mysqld file? Checked it too:
ls -la /usr/sbin/mysqld which returned
-rw-r--r-- 1 root root 24585896 Apr 30 10:52 /usr/sbin/mysqld
So the issue (I thought) was that user root didn't have the execute permission. Looks at the first three letters rw-. The last dash means no execution privilege.
So I simply ran the following chmod 777 /usr/sbin/mysqld, after which the ownership returns as
-rwxrwxrwx 1 root root 24585896 Apr 30 10:52 /usr/sbin/mysqld
Now, systemctl start mysql.service runs just fine.
It's amazing how simply the process of writing a question on stackoverflow actually helps me solve a problem 80% of the time. Thanks again, folks.