Why MySQL Keeps Crashing on an Ubuntu Server and How to Fix It

What is happening?

A cloud server is sometimes called a droplet. It is a small virtual computer you rent. MySQL is the program that stores your website's data in databases. When the server runs out of memory, Ubuntu may stop MySQL to save itself. Then your site shows "Error establishing a database connection".

The most common reason is too little RAM. RAM is the short-term memory a computer uses while it works.

Step 1: Check if memory ran out

1. Connect to your server with SSH.
2. Run this command:

sudo grep -i "out of memory" /var/log/syslog

This searches the system log for out-of-memory events. If you see "Killed process" and "mysqld", memory is the cause.

3. Check the MySQL log too:

sudo tail -n 50 /var/log/mysql/error.log

This shows the last 50 lines of MySQL's own notes.

Step 2: Add swap space

Swap is a part of the disk used as extra memory. It is slower than RAM, but it can stop crashes.

1. Create a 1 GB swap file:

sudo fallocate -l 1G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

These lines make the file, lock it down, prepare it as swap and turn it on.

2. Make it stay after a restart:

echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

Step 3: Make MySQL use less memory

Back up the config file first.

1. Copy the file: sudo cp /etc/mysql/mysql.conf.d/mysqld.cnf /root/mysqld.cnf.bak
2. Open it: sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf
3. Under [mysqld], add or lower these values:

innodb_buffer_pool_size = 128M
max_connections = 50

These limit how much memory MySQL takes and how many users can connect at once.

4. Save, then restart MySQL:

sudo systemctl restart mysql

Other causes

• The disk is full. Check with df -h.
• A broken table. Run mysqlcheck -u root -p --all-databases.
• Too many plugins or heavy traffic on your site.

Quick recap

• Most crashes come from running out of memory.
• Check the system log and MySQL log.
• Add swap space.
• Lower MySQL's memory settings.
• Upgrade RAM if it continues.