Navigation :

Long-Running and Uninterrupted Sessions

Guide to Long-Running and Uninterrupted Sessions

Warning: Never Store Passwords in Plain Text

Do not create or use custom scripts that read your password from a plain-text file to bypass timeouts. Storing your MIT or CSAIL password in plain text is a direct violation of MIT Password Policy. It is an extreme security risk. Always use the officially supported tools listed below instead.

By default, Kerberos tickets and AFS tokens expire to protect your account. However, if you are running long compute jobs or need a persistent workspace, you can use TIG’s custom utilities to automatically renew your credentials.

For most users, these tools can keep your session authenticated for up to 16 days (note: some older accounts may have shorter maximum renewable times). All TIG custom tools are located in /usr/local/csail/bin.

Tool Name	Type	Description	Important Notes & Caveats
`longscreen`	Detachable Interactive	Starts a standard GNU `screen` session while automatically renewing Kerberos tickets in the background.
`longtmux`	Detachable Interactive	Starts a `tmux` session with automatic ticket renewal.	MUST be the very first `tmux` session started on the machine. If attached to or started after another `tmux` session is already running, renewal will fail.
`longjob`	Non-Interactive	Wraps an arbitrary, non-interactive process (e.g., Slurm compute job, script) to ensure tickets are continuously renewed until completion or the maximum limit.
`longsession`	Persistent Interactive	Runs in the background of your current interactive shell to keep it authenticated.	You can reset the expiration timer indefinitely by manually re-authenticating with `kinit` before your max lifetime expires (e.g., once a week).
`krenew` / `k5start`	Standard Linux Utility	Securely wakes up and automatically renews Kerberos tickets in the background for normal shells.	Officially supported, standard utilities that do not require plain-text passwords.

General Limitations & Usage

macOS Users: Tickets forwarded via SSH from macOS are not renewable. You must manually run kinit once you log into the CSAIL machine to acquire a renewable ticket before using these tools.
Help Flags: Run any of the TIG custom scripts with the -h flag (e.g., longjob -h) in your terminal for more detailed usage instructions and syntax.
Checking your tickets: You can check the expiration time and max renewal time by using klist.

Valid starting       Expires              Service principal
04/08/2026 13:37:17  04/08/2026 23:37:17  krbtgt/CSAIL.MIT.EDU@CSAIL.MIT.EDU
        renew until 04/11/2026 10:08:32