If you want to back up your MySQL databases you’ll be familiar with

mysqldump -uroot -p --all-databases > dump.sql

However this includes the information_schema, mysql and performance_schema databases. These are often not only unwanted in the dump, but can potentially cause issues on import.

To exclude these databases from your dump use the following script courtesy of user RolandoMySQLDBA on the StackOverflow forums.

MYSQL_USER=root
MYSQL_PASS=rootpassword
MYSQL_CONN="-u${MYSQL_USER} -p${MYSQL_PASS}"
#
# Collect all database names except for
# mysql, information_schema, and performance_schema
#
SQL="SELECT schema_name FROM information_schema.schemata WHERE schema_name NOT IN"
SQL="${SQL} ('mysql','information_schema','performance_schema')"

DBLISTFILE=/tmp/DatabasesToDump.txt
mysql ${MYSQL_CONN} -ANe"${SQL}" > ${DBLISTFILE}

DBLIST=""
for DB in `cat ${DBLISTFILE}` ; do DBLIST="${DBLIST} ${DB}" ; done

MYSQLDUMP_OPTIONS="--routines --triggers --single-transaction"
mysqldump ${MYSQL_CONN} ${MYSQLDUMP_OPTIONS} --databases ${DBLIST} > all-dbs.sql