What the heck is a bus error?

ME dugan at passwall.com
Sat Mar 23 17:38:30 PST 2002


On Sat, 23 Mar 2002, Lincoln Peters wrote:
> It's 64MB of RAM, not 32MB.  And these errors appear as early as "Mounting 
> proc filesystem"!

I am sure you have done this, but the NFS exported /proc is empty, right,
and the dev directory (unless using devfs) has the necessary devices
right?

One of the other problems with exporting your own root for other machines
to use, is the /var/lock and other files normally set/reset on each
boot. It is really better to have a separate export that is clean/free of
these problems and allow each station to have its own /var, and /tmp as rw
or if you have enough memory (you prob dont) then use of a RAMDisk for
/tmp and /var. (The exported /tmp, /var/lock, and /proc dirs for each
station should be empty when they try to start in most cases.)

(Imagine exporting your own root as rw and then when the client boots, it
clobbers all your /tmp files and destroys all your /var/lock files. I am
sure there are likely other areas that I am forgetting at this moment.)

> I haven't even made a netbooting machine start up to the point where it can 
> run anything beyond what's shown in /etc/rc.d/rc.sysinit!
> 
> Is the mount command really that big a memory user?

Nope, not by itself. Not even close. I was assuming you had 32Mb on
clients and may have been running close to tolerance.

> Even if it's not related to this problem, it does sound like a good idea to 
> re-compile the /sbin programs to use shared libraries and conserve some 
> memory.  Anyone know how to do that on RedHat 7.2?  Should I just download 
> tarballs of all the programs in /sbin and manually re-compile them?

You should not need to do this. I was thinking you may have had some
scripts running at startup, sucking up memory (such as the locate database
update, or a few cronjobs with anacron or others or perhaps multiple
parallel copies of the same admin tool being called into existance.)

> I would try that if the errors were not occurring so early at boot time.  I 
> do have the system set up for virtual memory, but the NTFS module is not yet 
> available.  However, I should have enough memory to get a usable system at 
> runlevel 1 (so I can install the module), shouldn't I?

If you are getting these errors as early as mounting of proc, then any
libs/so used by mount may be corrupted or damaged (as sugested by the
other poster).

Use ldd to test the different bins you are trying to start that exhibit
these problems and see what libs/so are used by the bins (if any).

If you get bus errors and seg faults with any items that are staticly
linked, then you can look into hardware problems, or corrupt binaries, or
the above mentioned suggestions with looking at exporting an empty /proc.

-ME

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