How a Server Administrator Troubleshoots MySqlException (0x80004005)

First things first: is MySQL even running?

For closely related MySQL 0x80004005 topics, see MySql.Data 0x80004005 — Causes and Fixes, MySqlConnector Access Denied (admin), MySQL Corrupt Database Files, and native_password Access Denied.

systemctl status mysql

If I see "inactive (dead)", that means the MySQL service isn't running. Easy fix:

systemctl start mysql

If MySQL is running but acting weird, I restart it:

systemctl restart mysql

For Windows:

net start mysql

If that fixes it, great?I can go grab a coffee. If not, we go deeper.

Sometimes, error 0x80004005 is just MySQL refusing a connection due to incorrect credentials. I try logging in manually:

mysql -u root -p

If the password doesn't work, I reset it:

ALTER USER 'root'@'localhost' IDENTIFIED BY 'newpassword';
FLUSH PRIVILEGES;

Then, I update the password in .env or appsettings.json for the developers.

Sometimes, a user simply doesn't have the right permissions. I verify:

SELECT host, user FROM mysql.user;

If the host field says only localhost, and the application is connecting from another machine, I fix it by granting access:

GRANT ALL PRIVILEGES ON *.* TO 'myuser'@'%' IDENTIFIED BY 'mypassword';
FLUSH PRIVILEGES;

Then, I test the connection again.

If the database is completely corrupted and won't start, it's time for Plan B?restore from a backup. I check for the latest backup:

ls -lh /var/backups/mysql/

If I find a recent backup, I restore it:

mysql -u root -p < /var/backups/mysql/backup.sql

At this point, the developers can reconnect.