John's MySQL blog

 Warning: this will delete ALL your databases. After running this script it will let you automatically run mysql without a password (as root). Note this  is a security risk so do not run this on a production server. #!/bin/bash set -e # Function to remove MySQL and clean up remove_mysql() {     echo "Removing MySQL server and packages..."     sudo apt-get remove -y mysql-server mysql-client mysql-common     echo "Removing MySQL directories..."     sudo rm -rf /etc/mysql /var/lib/mysql /var/log/mysql /var/run/mysqld     # Clean up any residual packages and update package info     sudo apt-get autoremove -y     sudo apt-get clean } # Function to ensure MySQL configuration file exists ensure_mysql_config() {     if [ ! -f /etc/mysql/mysql.cnf ]; then         echo "Creating MySQL configuration file..."         echo "[client]" | sudo tee /etc/mysql/mysql.cnf         echo "user=root" | sudo tee -a /etc/mysql/mysql.cnf         echo "passw

  Fix: ERROR 1396 (HY000): Operation CREATE USER failed in MySQL? This is a mysql 8 bug. Suppose the user is  myuser . 1. The user already exists. Delete them with DROP. (not DELETE).      DROP USER myuser.     DO NOT use "delete from mysql.user where user=myuser". 2. You already deleted them with DELETE. Try it again with DROP, even if they do not exist.     If you are too late and you already made the mistake in (1) above you can either create a new user with a different name, e.g. myuser2, or, repeat the drop statement above in (1). 3. The password doesn't meet the default MySQL 8 requirements.     Sometimes it is because the password isn't good enough. It must be 8 chars minimum, with at least one caps, one lower, one number, and one punctuation. 4. Check your mysql supports old passwords ( mysql_native_password).    Use  CREATE USER 'myuser'@'localhost' IDENTIFIED WITH  mysql_native_password  BY 's0m3Passw0rd!@#';

It's way too difficult to restore a database using the /var/lib/mysql files. It's better to use mysqldump . Assume your database is named mydbname . mysqldump -u root -p mydbname > mydbname.sql This will dump out the SQL needed to recreate the database. Normally you want this as a cron job so it runs daily. Google how to make a cron job. Put the command into a script. You also want to gzip it because it's quite big and repetitive. The below is an example of a useful script. It saves the files with dates in the names so you can revert/restore the database from any date. Note however it embeds your password into the file, this is probably a bad idea™ but you can find a better solution yourself. One way is to create an authenticated user, let them run mysql without password ( saved password ), and set them run the script, ie use the username parameter in cron. #!/bin/sh uniquedate=`date +"%Y%m%d_%H%M%S-%s"` backuppath="/var/log/mysqldumps" [ ! -d $back

  To save a table into a CSV (spreadsheet) file: select * from TableName INTO OUTFILE '/var/lib/mysql-files/spreadsheet.csv' FIELDS ENCLOSED BY '"' TERMINATED by ';' ESCAPED BY '"' LINES TERMINATED BY '\n' This will drop the file into the folder /var/lib/mysql-files/

Sometimes moving a database file ( /var/lib/mysql/* ) breaks the records inside mysql's brain about what databases it had and what their tables were. If you did not use mysqldump to take backups, you are in trouble. Unfortunately if you do this, you have a long night ahead of you. However, help is at hand. A symptom of breaking Moodle in this way is you get this error:     Config table does not contain version, can not continue, sorry.     which means it cannot read the table mdl_config. The basic steps are: 1. Move your crashed/confused databases out the way so you don't break them further.  2. Recreate your mysql instance. 3. Recreate the databases and tables WITHOUT their contents (just the database names and table structures). 4. Tell mysql to forget their contents without using drop command (you use discard instead) 5. move your original db files back into place 6. Tell mysql to re-scan (import) the db files. 7. Create a timed script to run backups Here are the detailed st