Single base

# backup 
mysqldump -u root -p[root_password] [database_name] > dumpfilename.sql
# restore 
mysql -u root -p[root_password] [database_name] < dumpfilename.sql

All bases :

# backup 
mysqldump -u root -ptmppassword --all-databases > /tmp/all-database.sql
# restore 
mysql -u root -p[root_password] < dumpfilename.sql

!!! Les schémas doivent être vides avant le restore !!!