Run adduser non-interactively

Use the --gecos option to skip the chfn interactive part.

adduser --disabled-password --gecos "" username

It's all in the man page. Not the most obvious formulation tho.

--gecos GECOS
          Set  the  gecos field for the new entry generated.  adduser will
          not ask for finger information if this option is given.

The GECOS field is a comma separated list as such: Full name,Room number,Work phone,Home phone, despite that man page mentions finger information Details - Wikipedia

Hope this helps you.

useradd can also add users and does not appear to have any form of prompting built in.

useradd -m -p <encryptedPassword> -s /bin/bash <user>

• -m, --create-home: Create user home directory
• -p, --password: Specify user password; skip to have it disabled

• -s, --shell: Default shell for logon user

  Blank will use default login shell specified by the SHELL variable in /etc/default/useradd

• Substitute <user> with the login name
• Substitute <encryptedPassword> with the encrypted password

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Generating a hashed password:

There are a lot of crypt3 implementations that can generate a hashed password. The whole thing is your hashed password.

Sha-512 Based

The resulting output format: the hash mechanism ($6 for sha-512), the random salt (the eight bytes after the second dollar sign $ASDF1234), remainder is the payload.

• mkpasswd mkpasswd -m sha-512

  (mkpasswd is provided by the whois package)

DES based:

The resulting output format: first 2 bytes is your salt, remainder is the payload. The whole thing is your hashed password.

• mkpasswd: mkpasswd (provided by whois package)
• openssl: openssl passwd -crypt
• perl: perl -e "print crypt('password');"
• python: python3 -c 'import crypt; print(crypt.crypt("password"))'

You can combine what @ThorSummoner @Zoke are saying like so:

username=jovyan
password=jovyan

adduser --gecos "" --disabled-password $username
chpasswd <<<"$username:$password"

I'm doing this for my Jupyter docker-stack. It allows full headless setup in a Dockerfile.