[nzlug] ProFTPd 1.2.10 - terminating (signal 11) - Randomly.

[Michael Field]

Hi Michael

Memory going bad gives this behavior. Run diagnostics or maybe memtest
on the hardware. Do you have ECC memory in the system? If you are
running an important server without ECC memory, if so <insert lecture
here>.

As the kernel loads into and allocates it's memory in the same place
every time, it might run quite happily and only segfault user processes.

If you can't take the system down for memtest, perhaps do something that
will stress the box - do a "make clean; make all" of a kernel a few
times. 

If you do find that you have bad memory. I would be worried that the bad
bit(s) of memory has been used to buffer incoming data and could now be
corrupt. It might pay to verify checksums of important files if at all
possible. You might want to also fsck the entire disk too, incase of
metadata corruption.

Speeking from experience as somebody who repeatedly fscked a disk with
fs errors caused by bad memory, test the RAM first before you FSCK any
disk which has unexpectedly gone bad. 

Mike
-----Original Message-----
From: nzlug-bounces at linux.net.nz [mailto:nzlug-bounces at linux.net.nz] On
Behalf Of Michael Hutchinson
Sent: Thursday, 31 July 2008 10:01 a.m.
To: NZLUG Mailing List
Subject: [nzlug] ProFTPd 1.2.10 - terminating (signal 11) - Randomly.

Hello everyone,

 

We're currently having a problem on a major web server, with ProFTPd.
For a specific Client we host, 3 directories are a problem over an FTP
connection. Most of the time, when reading the directories in question,
the Server stops (with signal 11) and leaves the FTP client
disconnected. This only kills the child process on the server - and the
FTP client can reconnect again straight away. Retries on the FTP client
do produce a directory listing that works, but a simple refresh of the
directory can cause the FTP client to be disconnected again straight
away.

 

I had originally thought that this was a file naming convention problem,
but have disproved this by using another bunch of files in the
directories that have issues, and can reproduce the error using any
files.

I would then have expected a permissions problem with the directories
that fail listing - but no, they are exactly the same as every other
client we do hosting for - and none of them have this problem - besides
that, it wouldn't explain the randomness of the event. If there was a
permission problem, it would be a permanent one, not a random
experience.

 

I have tried Stack Tracing the ProFTPd main process and the child
process when one has logged in, but to no avail. Apart from failing
Reverse DNS lookups on occasion, that's all I see in the stack traces.
(I have since fixed the rDNS issue anyway and that hasn't helped).

 

I have noticed this error in the ProFTPd log file :

PAM(tile): User not known to the underlying authentication module.

Though this appears for every Client we host when logging in via FTP,
and never seems to cause a problem. 

 

I am unable to replicate the connection drop issue on other Client's
sites that we host. We've been hosting websites on this server for
years, and haven't come across a problem like this in that time. We're
running Debian Sarge (I know it is old) - but this helps the point that
not much has changed recently. 

 

Does anyone have some ideas as to what the problem might be? 

Thanks in advance,

 

Michael Hutchinson

Manux Solutions Ltd

| Phone: 0800 328 324

| Email: mhutchinson at manux.co.nz

| Web:   http://www.manux.co.nz/ 

 

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