Problems with lofs on Sun-3/4, SunOS 4.0, 4.0.1
Per Westerlund
perw at holtec.se
Fri Feb 10 16:11:27 AEST 1989
Using SunOS 4.0 (4.0.1) there is available a so called "loopback virtual
file system", lofs. The use of it is not apparent, but I would like to
use it to mount /var/tmp on /tmp, increasing the apparent size of /tmp,
without increasing the true size of the root partition. (Replacing /tmp
with a symbolic link to /var/tmp is not acceptable, makes single-user mode
without /var mounted a bit hard.)
All that should be needed is to add the following line to the config-file
options LOFS
and make a new kernel.
The file-system type is 'lo', and trial runs work,
mount -t lo /var/tmp /tmp
gives the desired result.
Next step is to modify /etc/fstab and /etc/rc to have this mounting
automatic. Add the line
/var/tmp /tmp lo rw 0 0
to /etc/fstab. Since I have looked at how this is done on the 386i, I add
a line to /etc/rc to make it look like this:
mount -at 4.2 >/dev/console 2>&1
mount -at lo >/dev/console 2>&1
THIS DOES NOT WORK! During startup this message appears:
"mount: unknown filesystem type: lo"
but the same command works as long as it is not run from within /etc/rc
(by init?).
A few possible explanations have been tried, without success:
- /etc/mount is statically linked.
- /sbin/mount is identical to (/usr)/etc/mount.
I have not been able to follow /etc/mount's doings with trace(1), since it
does a fork(2), and I loose it. Debugging with adb(1) without a symbol
table is so hard that I wont even think about it.
Ideas, someone?
Per Westerlund
Holistic Technology AB
Gothenburg
SWEDEN
+46 31 420370
perw at holtec.se
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