244

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?

312

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.

| improve this answer | |
  • off-topic Geckos? – Alex2php May 12 at 10:57
  • 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 at 21:44
51

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"))'
| improve this answer | |
  • 1
    The options you mention don’t exist for adduser on my (recent) version of Ubuntu. – ᴠɪɴᴄᴇɴᴛ Sep 22 '15 at 20:30
  • 2
    @ᴠɪɴᴄᴇɴᴛ adduser is distinct from useradd, confusing I know. – ThorSummoner Sep 22 '15 at 21:01
  • 1
    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
  • 1
    @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
  • 1
    @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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.