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I have some machines with RHEL4 Nahant Update 6. Oddly, I found that passwords longer than 8 digits are not stored.

So if I had a password 1ABCDEa!, and I changed it to 1ABCDEa!1ABCDEa! I could still log in to the machine with the old password.

This machines use NIS authentication, but other machines with Red Hat 5 which use the same NIS server allow login ONLY with the NEW password (16 digits long...)!

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It could be using the older crypt algorithm rather than something newer like MD5 or Blowfish, for backwards compatibility. Doesn't really explain the 8-char/16-char discrepancy, but searching for "NIS" and "MD5" might help. – Mikel Jan 19 '11 at 14:18
up vote 0 down vote accepted

There's a Red Hat KB article that discusses this.

It requires a Red Hat account. The executive summary is to use PAM. The article also references this URL for further reading:

Edited to add: See also this thread

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Thanks, I read this article before. I thought there is a way around it. But I think the solution they suggest does not work for me, because the server needs to be accessed via NIS, not PAM. – Oz123 Jan 21 '11 at 7:33

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