Documentation - Harper
Cluster Q & A
Please note: NSIT is no longer creating new accounts on harper. Individuals claiming or re-establishing their CNet accounts after the end of May 2009 will be unable to access harper.
Questions
- So what is "the Cluster" anyway?
- Pine is acting weird, what gives?
- The "mail" command is acting weird. How can I add a subject without getting a syntax error?
- Chfn/chsh stopped working, how do I change my GECOS field or shell?
- When I try to change my password, I get an error "Permission denied."
So what is "the Cluster" anyway?
Over the years we've tried a lot of configurations for email servers and interactive use servers, and generally found that, with the huge volume of usage and email we see on a daily basis, putting them all on one machine is a recipe for, if not disaster, then at least really, really slow email. To keep things moving smoothly, we use three main machines for email and interactive unix logins and several other machines for backend operation. As a user, you will probably only ever need to know about harper, midway, and plaisance, but square, ns, mach, web-proxy, and nsensa are also part of the operation. Currently they are all Sun machines running the Solaris operating system, a type of Unix.
Plaisance acts as the primary mailbox server for all user accounts. All email received by users is stored on plaisance, and plaisance spends its time giving people access to that email, via Eudora, pine, or whatever applications people use for that purpose.
Midway's primary purpose is to act as a middleman. All incoming email is actually delivered to midway (hence your midway email address); midway then hangs onto it until plaisance can accept it and stow it in the appropriate mailbox. (Thus, if plaisance is being heavily used for mail access for a period of time, it doesn't have to accept any new mail; midway will handle it. Similarly, if midway is dealing with receiving a lot of mail, it doesn't have to worry about people reading mail they've already received; plaisance is taking care of it.)/p>
Harper is primarily intended for interactive use. That's the machine NSIT provides for people who want to log on to a unix machine for email, programming, or other low-intensity computer work. Harper also acts as a relay for outgoing mail; when a Eudora user wants to send email to someone off-campus, harper can accept the mail and see to it that it ends up at the right place. You can, in theory, send email to someone @harper.uchicago.edu; in practice, what happens in such a situation is that harper hands the mail off to midway, which then delivers it to plaisance.
The other names floating around regarding email are nsit-email, nsit-popmail, and nsit-imap. These aren't actually machines; instead, they're sort of pointers or placeholders. The nsit-email pointer is intended to be "the place POP users send outgoing email through"; currently it's pointing to harper. The nsit-popmail pointer is "the place where POP users can download mail"; currently it's pointing to plaisance. The nsit-imap pointer is for use by people who interact with their email via IMAP. The reason to use pointers instead of machine names is that, if it becomes necessary, we can change things on this end without users needing to know about it. So, if the administrators decide to move all the mailboxes off plaisance to midway, we can just redirect the nsit-popmail pointer to midway; we don't have to notify 15,000 users that they need to change their configuration files. If we want to introduce a new machine to handle outgoing mail instead of harper, we just redirect the nsit-email pointer -- and again, no one has to update anything.
None of these pointers address where mail should be *sent* to you, though -- that's what the midway (username@midway.uchicago.edu) and ph alias (username@uchicago.edu) are for.
The other servers I mentioned are for providing services that users don't usually need to interact with directly. Square out NIS server, it is where passwords are stored and changed, and where new accounts are created. Ns has the database that ph information can be looked up on. Mach is for intensive user programs, such as compiling and statitics work. Web-proxy provides an authenticated web proxy service for machines off campus that need to access restricted information on the uchicago.edu network. And finally, nsensa.uchicago.edu is this web server for NSENSA documentation and information.
Pine is acting weird, what gives?
There were some problems upgrading Pine in the summer of 1999. If you are interested, there is a summary of pine problems that occured during the upgrade. If you are having problems, please contact technical support.
The "mail" command is acting weird. How can I add a subject without getting a syntax error?
Since the upgrade of harper in the summer of 1999, you will want to use the command "mailx" instead of just "mail". You will get the same behavior with "mailx" on the new system, that you enjoyed with "mail" on the old system. For example:
> mailx -s"your subject here" recipient@midway.uchicago.edu
message body here
.
EOF
OR
> mailx recipient@midway.uchicago.edu
Subject: your subject here
message body here
.
EOF
Chfn/chsh stopped working, how do I change my GECOS or shell?
The old system had separate commands for changing your password, shell, and GECOS field information. Under Solaris 7, all these functions are controlled by the command "passwd". Here is a brief summary of "passwd" options.
To change your password:
> passwd
To change your GECOS or Real Name Field (was chfn):
> passwd -g
To change your UNIX shell (was chsh):
> passwd -e
When I try to change my password, I get an error "Permission denied."
Because the password database gets rebuilt each hour on the hour, if you try to change your password more than once during an hour, you will get the error message "Permission denied." Please wait to change your password again.
Last updated: 6/23/09