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Paul Hoffman
Asked: 2011-12-01 08:43:30 +0800 CST

Can I change a user password in Linux from the command line with no interactivity?

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I have a specific use case where I would really like to be able to change a user's password with a single command with no interactivity. This is being done in a safe fashion (over SSH, and on a system with only one user able to be logged in), so it's fine to expose the new password (and even the old one, if necessary) on the command line. FWIW, it's a Ubuntu system.

I just want to avoid having to add something Expect-like to this system for just this one task.

ubuntu command-line-interface password freebsd

5 Answers

  1. Best Answer

    You could use chpasswd.

    echo user:pass | /usr/sbin/chpasswd
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  2. You can use usermod with the -p option to provide a password hash (not the actual password). You can generate the password hash using something like mkpasswd -m sha-256 or mkpasswd -m md5

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  3. Sure.

    1. Hash the password on your local system.
    2. Connect to the remote machine (where you want to change the password)
    3. Feed the hashed password & the username to a creative sed script that updates your system's password file (/etc/shadow, /etc/master.passwd, whatever it happens to be).
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  4. The passwd utility has a --stdin option that states:

    This option is used to indicate that passwd should read the new password from standard input, which can be a pipe.

    Syntax:

    echo "newpass" | passwd --stdin user1

    Even though you mentioned you don't care, you could put the password in a text file and then do cat pass.txt instead of the echo command, that way it doesn't show up in the bash history.

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  5. If --stdin option is not working we can basically use two options:

    1. Either use another utilty called chpaswd in your script.
    2. OR use echo "current_password\nnew_password\nnew_password" | passwd user_name
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