Username Length and Password Expiry

Darren Tucker dtucker at
Thu Mar 2 08:42:43 EST 2006

On Wed, Mar 01, 2006 at 01:24:38PM -0800, mark clarkson wrote:
> Thanks Darren.  I know that useradd warns you but it does create the
> ID on the system.

There appears to be a good reason for the warning:
$ telnet localhost
login: abcdefghi
$ id
uid=517(abcdefghi) gid=1(other) groups=1(other)
$ passwd
passwd: Changing password for abcdefgh
passwd: User unknown: abcdefgh
Permission denied

passwd is a setuid binary and doesn't really know your login name.
It does know your real uid, though.  It is probably looking that up
with getpwuid(), and it would appear that it or passwd itself does not
support usernames of more than 8 characters.

So your options appear to be 1) shorten the username or 2) use PAM.

Darren Tucker (dtucker at
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
    Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.

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