Set password aging options on NIS password

[Travis Rebok]

I am Running NIS on HP 11.0. I created a script to generate new encrypted passwords for users in a specific user group. Then I update the /etc/passwd file. However I see the following format in the /etc/passwd file for some users:

user:password,MmNN:uid:gid:gecos:path:shell
M=max (.=0,/=1,0=2,9=11,A=12,Z=37,a=38,z=63)
m=min
NN=time password was changed last time

I know that the M, m, and NN are used for password aging. I imagine I can just leave the values for M and m alone, but how do I calculate a new value for NN?
When I "man 4 passwd" it says that NN define the week (counted from the beginning of 1970) when the password was last changed. To test this I just changed my password today and the values for NN are "IO". How does "IO" or the digit values "I"=20 and "O"=26 correlate to what the man page is saying. How can I generate these values when I run my process to manually generate encrypted passwords?
Thanks.

[A. Clay Stephenson · Accepted solution]

The current week is encoded as a base-64 2-digit number drawn the from the character set ./0123456789A-Za-z. The most significant digit appears last.

Lets suppose that the cuurent week is 64 weeks since the beginning of time (Jan 1, 1970).
That would be encoded as 1 x 64^^1 + 4 x 64^^0 or "2/" from the above character set in REVERSE order. 2 ==> 4 and / ==> 1.

Fortunately, I already had a small perl script to do this. It simply takes the current date and outputs the encoded value to stdout.

Use it like this:

PWAGE=$(pwage.pl)
echo "PWAGE (Current Date) = \"${PWAGE}\""

[S.K. Chan]

Just FYI ..

If you made a password change on 3/5/02 (tue), the information you got if you run ..

# logins -x -l

will show it's changed on 2/28/02 (thur) instead, because of the starting time on 1/1/70 (which is thur) the last password change will be on Thursday before the actual modification day.

[A. Clay Stephenson]

Oops.... I meant 68 rather than 64 weeks in my above example.


Lets suppose that the cuurent week is 68 weeks
(14 base-64) since the beginning of time (Jan 1, 1970).
That would be encoded as 1 x 64^^1 + 4 x 64^^0 or "2/" from the above character set in REVERSE order. 2 ==> 4 and / ==> 1.

This is a slighty cleaner version of the Perl script as well although the above example works just fine.

[Travis Rebok]

Yeah I was alittle confused by your first example. Thanks for the clarification.
I can convert the perl to java to my use. However if
my $curr_wk = time() / SECONDS_PER_DAY / DAYS_PER_WK; gives the week number(since 1/1/1970), do you know a comparable function to Perl's time() in unix shell or java since I cannot use Perl for my app?

[A. Clay Stephenson]

Dte has a 'UTC' method which returns the number of milliseconds since Jan 1, 1970 UTC. Divide that value by 1000 and there you are.

[Travis Rebok]

Perfect. I used Date.getTime()to get millisecs and the logic you provided in your program. Works great and gives me "OJ" for today like expected. Thanks alot for your help!
Travis

[Travis Rebok]

Oops, forgot to REVERSE them... "JO" just like I expected.