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Considerations when running processes in the background on WAM/Glue when not logged on

Some things to note:

1. All WAM RACs (accessed via "wam.umd.edu") and the default Glue systems (accessed via "glue.umd.edu") get rebooted nightly around 03:00.
2. The user authentication system on WAM and Glue, Kerberos, creates tickets when you login which allow you to work on the system. These tickets have a 25 hour lifespan; once they expire, the login session loses its rights to access certain areas of the system, including writing to your file space.

   If you need to write to files beyond the 25-hour lifetime of standard WAM and Glue Kerberos authentication tickets, you will need to submit a WAM/Glue request to have the lifetime of your personal tickets lengthened. If you suspect your job(s) will take longer than 25 hours to run, you'll need to try to determine just how long it will be, and then use request to ask that your Kerberos tickets stay alive that long.

One last thing; if you do plan on starting a long-running job and you've been on the system for some amount of time already, you can renew your Kerberos tickets to get another 25 hours by typing the command:

renew

You'll be asked for your login password to verify it's you, and assuming you enter the correct password, your Kerberos tickets will be renewed for another 25 hours. To see how long you have until they expire, you can use the klist command:

    klist
    Ticket file:    /tmp/tktUID
    Principal:      USERID@GLUE.UMD.EDU

      Issued           Expires          Principal
    Dec 22 08:23:02  Dec 23 09:49:23  krbtgt.GLUE.UMD.EDU@GLUE.UMD.EDU
    Dec 22 08:23:02  Dec 23 09:49:23  afs@GLUE.UMD.EDU

where UID is the unique numeric ID number associated with every userid on the system, and USERID is the associated userid. In this example, the tickets were initiated at 08:23 on December 22nd, and will expire at 09:49 on December 23rd, assuming the user is still logged on. If they type renew, the klist will then show something like:

    klist
    Ticket file:    /tmp/tkt273
    Principal:      user@GLUE.UMD.EDU

      Issued           Expires          Principal
    Dec 22 16:07:29  Dec 23 17:33:50  krbtgt.GLUE.UMD.EDU@GLUE.UMD.EDU
    Dec 22 16:07:29  Dec 23 17:33:50  afs@GLUE.UMD.EDU

Now they're updated to 4:07 p.m. December 22nd, and will last until 5:33 p.m. on December 23rd.