Dear LWP Users,

lwp24, the home directory server of the LWP, will be rebooted next
Sunday night. This will only take about two minutes, and it will happen
between Sunday September the 18th 9:00 pm and Monday the 19th 7:00 am.
But I don't yet know precisely at what time.
Half an hour before the reboot, I'll send a notification mail to those
who are logged in at that moment.

Consequences
------------
If you are not logged in at the time of the reboot, then it has no
consequences for you. If you leave your PC logged in but you are not at
the keyboard, experience so far says that most likely you won't notice
either.

But if you remain logged in *and* you have processes doing I/O to your
home directory, then you may notice a freeze during the reboot.
And if your process(es) are doing enough I/O, they may even *crash*.

How to still perform lengthy computations this weekend
------------------------------------------------------
If you have computations to run on your LWP that must be carried out
this weekend, then please take the following measures:
- Start the computing program from the shell instead of a GUI.
Mathematica, Matlab and Maple all have command line interfaces that
don't require X Windows. Sometimes particular options are required (see
example below).
- Before starting the program, cd to /mnt/D, so your working directory
is on the hard disk of the PC, not in your home directory.
Let the program do its I/O to the disk instead of $HOME as well, and
copy the results to $HOME on Monday.
- Use 'nohup' and/or file redirection so the program reads and writes to
file instead of the terminal.
- Use 'disown' to prevent Bash from sending the program a SIGHUP when
Bash is stopped.
- You may even log out now, the program will continue to run.
- As an example:
me@host:~$ cd /mnt/D
me@host:/mnt/D$ nohup matlab \
-nosplash \
-nojvm \
-nodisplay \
< lenghty_computation.m &
me@host:/mnt/D$ disown
me@host:/mnt/D$ logout

As for computations that are already running, especially those with GUIs
attached, these cannot in all cases be saved.

Why the server must be restarted
--------------------------------
Last weekend and the weekend before, the LWP homedir server went down
unexpectedly. We found that this was because it ran out of memory.
Whether this is caused by a memory leak or some misconfiguration, we
cannot yet tell. After some measures, it is not consuming memory as
quickly any more, but I'm not confident that it will last another full
week. (About half of its memory is still free after five days' uptime.)
If we reboot it just before Monday however, it 'll stay up for another week.

During that week, we will prepare an upgrade of its software, which may
well fix the machine. So it is likely that during the weekend of the
24th the server will have to be brought down for maintenance, or at
least rebooted again to free up some memory.

We apologize for the inconvenience.

Kind Regards,
Jurjen (for all LWP admins)