228 System Administration
system because the boot process will clear out all the crud that accumulated
in the /tmp directory. So now you know why the boot process cleans out
/tmp.Making a “large” partition containing the /tmp directory, for the times
when a program may actually need all that space to work properly, just
moves the problem around: it doesn’t solve anything. It’s a shell game.
That space so carefully reserved in the partition for the one or two times
it’s needed can't be used for things such as user files that are in another par-
tition. It sits idle most of the time. Hey, disks are cheap these days. But no
matter how big you make /tmp, a user will want to sort a file that requires a
a temporary file 36 bytes larger than the /tmp partition size. What can you
do? Get your costly sysadmin to dump your whole system to tape (while it
is single-user, of course), then repartition your disk to make /tmp bigger
(and something else smaller, unless buying an additional disk), and then
reload the whole system from tape. More downtime, more cost.
The swap partition is another fixed size chunk of disk that frequently turns
out not to be large enough. In the old days, when disks were small, and fast
disks were much more expensive than slow ones, it made sense to put the
entire swap partition on a single fast, small drive. But it no longer makes
sense to have the swap size be a fixed size. Adding a new program (espe-
cially an X program!) to your system often throws a system over the swap
space limit. Does Unix get unhappy when it runs out of swap space? Does a
baby cry when it finishes its chocolate milk and wants more? When a Unix
system runs out of swap space, it gets cranky. It kills processes without
warning. Windows on your workstation vanish without a trace. The system
gives up the ghost and panics. Want to fix the vanishing process trick prob-
lem by increasing swap space? Get your costly sysadmin to dump your
whole system to tape (while it is single-user, of course), then repartition
your disk to make /swap bigger, and then reload the whole system from
tape. More downtime, more cost. (Sound familar?)The problem of fixed size disk partitions still hurts less now that gigabyte
disks are standard equipment. The manufacturers ship machines with disk
partitions large enough to avoid problems. It’s a relatively expensive solu-
tion, but much easier to implement than fixing Unix. Some Unix vendors
now swap to the file system, as well as to a swap partition, which helps a
bit, though swapping to the file system is much slower. So Unix does
progress a little. Some Unix venders do it right, and let the paging system
dynamically eat into the filesystem up to a fixed limit. Others do it wrong
and insist on a fixed file for swapping, which is more flexible than refor-
matting the disk to change swap space but inherits all the other problems. It
also wreacks havoc with incremental nightly backups when using dump,