If I add a user with no home directory, do they have a password?

Question

Referencing the answers to this question, they give nifty one-liners to create such a user such as:

sudo adduser --system --no-create-home --group mightydog

After this, can user mightydog log on? What is his password?

Answer 1

There's no harm in simply trying it out. On my system (16.04), this resulted in a user with locked password (*) and no valid login shell (/bin/false), as can be seen from its /etc/passwd and /etc/shadow entry:

# grep mightydog /etc/passwd
mightydog:x:128:138::/home/mightydog:/bin/false

# grep mightydog /etc/shadow
mightydog:*:17610:0:99999:7:::

So no, it does not have a password, and it also can not log in by any other means (like SSH keys, or using sudo -u) due to the /bin/false shell.