Note: You don't actually want all DB's, you want to ignore the schema DB's and mysql.
Use the following:
https://dba.stackexchange.com/a/69667/113202
cat << 'EOF' >mysql_all_db_dump.sh
#!/bin/bash
#https://dba.stackexchange.com/a/69667/113202
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
EOF
chmod +x mysql_all_db_dump.sh
./mysql_all_db_dump.sh
Import:
mysql -u root -p < all-dbs.sql