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<title>The Exim FAQ Section 25</title>
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<h1>The Exim FAQ</h1>
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<h2><a href="FAQ.html#TOC383">96. LINUX</a></h2>
<p>
<a name="TOC384" href="FAQ.html#TOC384">Q9601:</a> Exim is mysteriously crashing, usually when forking to send a delivery
error message.
</p>
<p>
<font color="#00BB00">A9601:</font> This has been seen in cases where Exim has been incorrectly built with
a muddled combination of an <i>ndbm.h</i> include file and a non-matching
DBM library.
</p>
<p>
Faults like this have also been seen on systems with faulty motherboards.
You could try to compile the Linux kernel 10 times - if the compile
process stops with signal 11, your hardware is to blame.
</p>
<p>
<a name="TOC385" href="FAQ.html#TOC385">Q9602:</a> I want to use <i>logrotate</i> which is standard with RH5.2 Linux to rotate
my mail logs. Anyone worked out the <i>logrotate</i> config file that will
do this?
</p>
<p>
<font color="#00BB00">A9602:</font> Here's one suggestion:
</p>
<pre>
/var/log/exim/main.log {
create 644 exim exim
rotate 4
compress
delaycompress
}</pre>
<p>
The sleep is added to allow things to close the log file prior to
compression. You also need similar entries for the panic log and the
reject log, of course.
</p>
<p>
<a name="TOC386" href="FAQ.html#TOC386">Q9603:</a> I'm seeing the message <i>inetd[334]: imap/tcp server failing (looping),
service terminated</i> on a RedHat 5.2 system, causing <i>imap</i> connections to
be refused. The <i>imapd</i> in use is Washington Univers 12.250. Could this
be anything to do with Exim?
</p>
<p>
<font color="#00BB00">A9603:</font> No, it's nothing to do with Exim, but here's the answer anyway: there
is a maximum connection rate for <i>inetd</i>. If connections come in faster
than that, it thinks a caller is looping. The default setting on RedHat
5.2 is 40 calls in any one minute before <i>inetd</i> thinks there's a problem
and suspends further calls for 10 mins. This default setting is very
conservative. You should probably increase it by a factor of 10 or 20.
For example:
</p>
<pre>
imap stream tcp nowait.400 root /usr/sbin/tcpd /usr/local/etc/imapd</pre>
<p>
The rate setting is the number following “nowait”. This syntax seems to
be specific to the Linux version of <i>inetd</i>. Other operating systems
provide similar functionality, but in different ways.
</p>
<p>
<a name="TOC387" href="FAQ.html#TOC387">Q9604:</a> I get the <i>too many open files</i> error especially when a lot of messages
land for Majordomo at the same time.
</p>
<p>
<font color="#00BB00">A9604:</font> The problem appears to be the number of open files the system can
handle. This is changable by using the proc filesystem. To your
<i>/etc/rc.d/rc.local</i> file append something like the following:
</p>
<pre>
# Now System is up, Modify kernel parameters for max open etc.</pre>
<pre>
if [ -f /proc/sys/kernel/file-max ]; then
echo 16384 >> /proc/sys/kernel/file-max
fi
if [ -f /proc/sys/kernel/inode-max ]; then
echo 24576 >> /proc/sys/kernel/inode-max
fi
if [ -f /proc/sys/kernel/file-nr ]; then
echo 2160 >> /proc/sys/kernel/file-nr
fi</pre>
<p>
By echoing the value you want for file-max to the file <i>file-max</i> etc.,
you actually change the kernel parameters.
</p>
<p>
<a name="TOC388" href="FAQ.html#TOC388">Q9605:</a> I installed debian 2.2 linux on a small 325mb 486 laptop. When I try
to test the Mail program, I get the following error: <i>Failed to open
configuration file /etc/exim.conf</i>.
</p>
<p>
<font color="#00BB00">A9605:</font> The Debian installation should have given you <i>/usr/sbin/eximconfig</i>,
which asks you some questions and then sets up the configuration file
in <i>/etc/exim.conf</i>. Try running that (you'll probably need <i>root</i>) and see
how it goes. In any case you get a thoroughly commented conf file at
the end, which will give you a sample from which to work if you need
further modification.
</p>
<p>
The Exim docs in the Debian package are in <i>/usr/doc/exim</i> where the full
reference manual is <i>spec.txt.gz</i>.
</p>
<p>
<a name="TOC389" href="FAQ.html#TOC389">Q9606:</a> I'm having trouble configuring Exim 4 on a Debian system. How does
<i>/etc/exim4/conf.d</i> work?
</p>
<p>
<font color="#00BB00">A9606:</font> The Debian Exim 4 package uses a quite uncommon, but elegant,
method of configuration where the “real” Exim configuration file is
assembled from a tree of snippets by a script invoked just before the
daemon is started (see <a href="FAQ_25.html#TOC391">Q9608</a>).
</p>
<p>
This fits very well into the Debian system of configuration file
management and is a great ease for the automatic configuration with
Debconf. However, it is very different from the normal way Exim 4 is
configured. Non-Debian users on the Exim mailing list will probably have
difficulty in trying to answer specific questions about it. You may have
to find a Debian expert.
</p>
<p>
<a name="TOC390" href="FAQ.html#TOC390">Q9607:</a> I'm having difficulties trying to make Exim 4 with Redhat 9 and Berkeley
DB 4.
</p>
<p>
<font color="#00BB00">A9607:</font> Have you remembered to install the db4-devel package?
</p>
<p>
<a name="TOC391" href="FAQ.html#TOC391">Q9608:</a> I'm running Exim 3 under Debian, and want to upgrade to Exim 4. How
difficult is it?
</p>
<p>
<font color="#00BB00">A9608:</font> A user who did this, using the Debian Exim 4 package, reported as
follows:
</p>
<p>
(1) The exim4 package installs easily, and the exim (3.38) package
uninstalls at the same time.
</p>
<p>
(2) Exim runs from <i>inetd</i>. Exim4 runs from <i>/etc/init.d</i>. Much nicer!
</p>
<p>
(3) The exim conffile lives in <i>/etc/exim/exim.conf</i>. The exim4 conffile
lives in <i>/var/lib/exim4/config.autogenerated</i>. It is, as the name
suggests, autogenerated.
</p>
<p>
(4) A new directory is created called <i>/etc/exim4</i>. This contains the
conffiles to generate the above config. You make changes here.
</p>
<p>
(5) Once you have made changes to the files in <i>/etc/exim4</i> you run the
script <i>update-exim4.conf</i> which generates a replacement
<i>config.autogenerated</i>.
</p>
<p>
[Added comment by the Debian maintainer, slightly edited:
You also need to tell the Exim daemon to reread the changed
configuration. You can do this using SIGHUP by hand. Alternatively,
instead of running <i>update-exim4.conf</i> you can use
</p>
<pre>
invoke-rc.d exim4 reload</pre>
<p>
which does the rebuild and also tells Exim to reread the changed
configuration.]
</p>
<p>
(6) In my experience, you need to carefully check the generated
configs. eg, it did not generate a system filter file reference in the
<i>config.autogenerated</i>. I didn't bother too much, since this is a home
setup.
</p>
<p>
(7) All of this may be in the docs. I've read some of them, obviously,
but didn't come across an actual upgrade guide.
</p>
<p>
[The Debian maintainer says:
<i>/usr/share/doc/exim4-base/README.Debian.gz</i> and <i>update-exim4.conf(8)</i>
should answer most of the questions.]
</p>
<p>
(8) I've still got some minor things to tweak to get back to where I
was before with Exim 3. But overall, it's no drama.
</p>
<p>
<a name="TOC392" href="FAQ.html#TOC392">Q9609:</a> Why do some servers refuse SMTP connections from my Linux box, but accept
connections from hosts running other operating systems?
</p>
<p>
<font color="#00BB00">A9609:</font> If you are sure this isn't a policy issue (that is, your box isn't
administratively blocked for some reason), this may be because your
Linux box has ECN (Explicit Congestion Notification) enabled in its
TCP/IP stack. There are many broken firewalls that refuse connections
from ECN-enabled hosts. You can check the state of your box by running
</p>
<pre>
cat /proc/sys/net/ipv4/tcp_ecn</pre>
<p>
If the value is "1", you have ECN enabled. You can turn it off by
running this command:
</p>
<pre>
echo "0" > /proc/sys/net/ipv4/tcp_ecn</pre>
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