Changing password is prevented

If two accounts have the same user ID, then by definition they are the same account. It is possible, but not recommended, to have more than one line in /etc/passwd (or other user database) with the same user ID; they are the same user, with different ways to log in.

You were using an unsupported feature. The risk of using an unsupported feature is that it sometimes breaks when the system is upgraded.

Expiring password is usually bad for security, as it causes users to choose weaker passwords or write them down on a post-it note stuck to the monitor. The only security benefit to expiring passwords is to eventually lock out abandonned accounts. Since the abc account is presumably one that you use as part of some kind of regular task, don't expire it.

You should probably change this setup, as it's fragile. What to change it do depends on what you use the abc account for (who has the password, in what circumstances it's used, what's abc's shell, is it present on multiple machines, …).

Try restructuring your PAM chain like this for file, /etc/pam.d/common-password:

password required pam_pwcheck.so
password required pam_cracklib.so use_authtok minlen=10 retry=3 minclass=3
password required pam_pwcheck.so remember=5 use_authtok use_first_pass
password required pam_unix2.so nullok use_authtok use_first_pass

I found the above and modified it slightly from this Novell document titled: using pam_pwcheck and pam_cracklib at the same time.

Additionally I used these as resources:

• pam_pwcheck man page
• pam_cracklib man page
• pam man page