Mysqldump Command - Useful Usage Examples

One of the tasks a sysadmin will always have on their list is backing up databases. These backups are also called dump files because, usually, they are generated with mysqldump command.

I am going to share a few tricks on mysqldump that will help when handling servers with many relatively small databases.

The most simple way to backup databases would be using mysqldump command with the the --all-databases attribute. But I find that having each database saved in its own file more convenient to use.

Lets first suppose that you need to run a script that alters in databases, and that you just need a simple way to have a rollback point, just in case. I used to run something like this before:

for i in \
`ls /var/lib/mysql/`; \
do mysqldump -u root -p*** --skip-lock-tables --skip-add-locks --quick --single-transaction $i > $i.sql; done

where *** is your root password. The aditional parameters --skip-lock-tables --skip-add-locks --quick --single-transaction  assure availability and consistency of dump file for InnoDB databases (the default storage engine as of MySQL 5.5.5).

Mysql stores databases in folders using same name as database name in /var/lib/mysql. The command picks database names from the listing of /var/lib/mysql folder and exports to files using same name adding the .sql.

There are 2 issues with the above command:

1. It will try to execute a dump for every file/folder listed in /var/lib/mysql. So if you have error logs or whatever other files it will create .sql dumps for them too. This will send just directory names as database names to export:

   for i in \
   `find /var/lib/mysql/ -type d | sed 's/\/var\/lib\/mysql\///g'`;\
   do mysqldump -u root -p*** --skip-lock-tables --skip-add-locks --quick --single-transaction $i > $i.sql; done

   I find this to be hard to type and prefer to use one I will explain in point 2, since it also covers this.

2. When database names have characters like - the folder name will have @002 instead. If that is the case, you can use something like:

   for i in \
   `mysql -u root -p*** -e 'show databases'`;\
   do mysqldump -u root -p*** --skip-lock-tables --skip-add-locks --quick --single-transaction $i > $i.sql;done

   This picks database names to export form mysql show databases command.

But, one time I had to export databases with /  in their names. And there is no way to export as I showed above, since / can’t be used in file names since it is actually a markup for directories.  So I did this:

for i in \
`mysql -u root -p*** -e 'show databases'`;\
do mysqldump -u root -p*** --skip-lock-tables --skip-add-locks --quick --single-transaction $i > `echo $i | sed "s/\//_/g"`.sql;done

This wil replace / with _ for the dump file names.

For all of the above, we could (for obvious reasons) not use root mysql user.  We could also run the backing up from a different location. In order to do this, we would need to create a mysql user with the right privileges on the machine we want to back up.

create user 'backupuser'@'111.222.333.444' identified by 'backuppassword';

grant select, show view, trigger, lock tables, reload, show databases on *.* to 'backupuser'@'111.222.333.444';
flush privileges;

where 111.222.333.444 is the ip of the remote machine.

Now you can issue mysqldump command from the other machine like this:

for i in \
`mysql -u backupuser -pbackuppassword -e 'show databases'`;\
do mysqldump -u backupuser -pbackuppassword -h 444.333.222.111 --skip-lock-tables --skip-add-locks --quick --single-transaction $i > `echo $i | sed "s/\//_/g"`.sql;done

where 444.333.222.111 is the ip of the machine we want to backup.

Lets take it to the next step , and put all our knowledge in a shell script.

#!/bin/bash
echo "Starting the backup script..."
ROOTDIR="/backup/mysql/"
YEAR=`date +%Y`
MONTH=`date +%m`
DAY=`date +%d`
HOUR=`date +%H`
SERVER="444.333.222.111"
BLACKLIST="information_schema performance_schema"
ADDITIONAL_MYSQLDUMP_PARAMS="--skip-lock-tables --skip-add-locks --quick --single-transaction"
MYSQL_USER="backupuser"
MYSQL_PASSWORD="backuppassword"

# Read MySQL password from stdin if empty
if [ -z "${MYSQL_PASSWORD}" ]; then
 echo -n "Enter MySQL ${MYSQL_USER} password: "
 read -s MYSQL_PASSWORD
 echo
fi

# Check MySQL credentials
echo exit | mysql --user=${MYSQL_USER} --password=${MYSQL_PASSWORD} --host=${SERVER} -B 2>/dev/null
if [ "$?" -gt 0 ]; then
 echo "MySQL ${MYSQL_USER} - wrong credentials"
 exit 1
else
 echo "MySQL ${MYSQL_USER} - was able to connect."
fi

#creating backup path
if [ ! -d "$ROOTDIR/$YEAR/$MONTH/$DAY/$HOUR" ]; then
    mkdir -p "$ROOTDIR/$YEAR/$MONTH/$DAY/$HOUR"
    chmod -R 700 $ROOTDIR
fi

echo "running mysqldump"
dblist=`mysql -u ${MYSQL_USER} -p${MYSQL_PASSWORD} -h $SERVER -e "show databases" | sed -n '2,$ p'`
for db in $dblist; do
    echo "Backuping $db"
    isBl=`echo $BLACKLIST |grep $db`
    if [ $? == 1 ]; then
        mysqldump ${ADDITIONAL_MYSQLDUMP_PARAMS} -u ${MYSQL_USER} -p${MYSQL_PASSWORD} -h $SERVER $db | gzip --best > "$ROOTDIR/$YEAR/$MONTH/$DAY/$HOUR/`echo $db | sed 's/\//_/g'`.sql.gz"
        echo "Backup of $db ends with $? exit code"
    else
        echo "Database $db is blacklisted, skipped"
    fi
done
echo 
echo "dump completed"

This will also compress the dump files to save storage.

Save the script as backup-mysql.sh somewhere on the machine you want backups saved, ensure you have the mysql user with the right credentials on the server hosting the mysql. You will also need mysql installed on the backup server. Executesudo chmod 700 backup-mysql.sh. Run the script with sudo sh backup-mysql.sh . After making sure it works properly, you can also add it to your crontab, so that it runs on a regular schedule.