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I'd like to use the adduser command to add a user (with disabled password) via a shell script.

By default, adduser prompts you for various values (e.g., Full Name). Is there any way to submit these values via command line? Or will I need to useradd instead?

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365

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.

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    off-topic Geckos?
    – Alex2php
    May 12 '20 at 10:57
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    Some early Unix systems at Bell Labs used GECOS machines for print spooling and various other services, so this field was added to carry information on a user's GECOS identity (source: en.wikipedia.org/wiki/Gecos_field)
    – Zoke
    May 12 '20 at 21:44
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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

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"))'
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  • 1
    The options you mention don’t exist for adduser on my (recent) version of Ubuntu.
    – ᴠɪɴᴄᴇɴᴛ
    Sep 22 '15 at 20:30
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    @ᴠɪɴᴄᴇɴᴛ adduser is distinct from useradd, confusing I know.
    – ThorSummoner
    Sep 22 '15 at 21:01
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    Oops, indeed missed that you use its almost namesake … isn’t there a BDFL protecting the command line namespace? ;p
    – ᴠɪɴᴄᴇɴᴛ
    Sep 23 '15 at 9:52
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    @mum007 This is only general advice, try adding -v or -vv or -vvv to your ssh commands to see whats wrong and search your error messages here on SO or Google.
    – ThorSummoner
    Dec 3 '15 at 17:30
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    @KovacsAkos try this: sudo sed -i"" -e "s/PasswordAuthentication no/PasswordAuthentication yes/" /etc/ssh/sshd_config and sudo service ssh restart
    – JSBach
    Apr 5 '17 at 9:01
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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.

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  • 1
    +1 for chpasswd. Much easier than fiddling with mkpasswd to make the hashes manually, and way more script-friendly.
    – J.D. Mallen
    Jul 5 '21 at 23:37
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    This was very helpful. Thanks.
    – codegeek
    Nov 23 '21 at 0:56

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