psql: FATAL: Peer authentication failed for user

I just installed PostgreSQL 9.4 on Ubuntu 15.10. 1. I created a user with createuser -P myuser 2. I created a database with createdb -O myuser mydatabase 3. I edited pg_hba.conf and added local mydatabase myuser md5 4. I restarted PostgreSQL with sudo service postgresql restart User *myuser* is a PostgresSQL user only and has no user account on Ubuntu. **When I try to connect to the database with psql -W mydatabase myuser it fails with psql: FATAL: Peer authentication failed for user "myuser".** PostgreSQL is running … ● postgresql.service - PostgreSQL RDBMS Loaded: loaded (/lib/systemd/system/postgresql.service; enabled; vendor preset: enabled) Active: active (exited) since Thu 2016-03-03 09:53:00 CET; 9min ago Process: 22219 ExecStart=/bin/true (code=exited, status=0/SUCCESS) Main PID: 22219 (code=exited, status=0/SUCCESS) Mar 03 09:53:00 SERVER01 systemd: Starting PostgreSQL RDBMS... Mar 03 09:53:00 SERVER01 systemd: Started PostgreSQL RDBMS. ... and listening. Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 localhost:postgresql *:* LISTEN tcp6 0 0 localhost:postgresql [::]:* LISTEN Active UNIX domain sockets (only servers) Proto RefCnt Flags Type State I-Node Path unix 2 [ ACC ] STREAM LISTENING 151534 /var/run/postgresql/.s.PGSQL.5432 **What do I have to do to connect with user *myuser* to database *mydatabase*?**