sysctl.conf

[Rick Stevens]

Allen, Jack wrote:
> Is there a document that describes all the parameters and there values 
> that can be put in the sysctl.conf file. The man page says see 
> /proc/sys, but you still have to figure out what valid values would be 
> for each. And some I have no idea what they really control. I am moving 
> an Application from UNIX to Linux and had kernel parameter requirements 
> that had to be set in UNIX for the application to run correctly. Things 
> like:
> 
> NPROC                   Maximum number of processes the system can have 
> at once.
> MAXUPROC                Maximum number of processes that a non-super 
> user can have at once.
> MAXFILES                Default number of file descriptors a process is 
> allowed to have at once.
> NFILES                  The maximum number of open files for the entire 
> system.
> 
> I know some of these may not even exist in Linux as a tunable parameter 
> or have a higher value than the application requires, but it would be 
> nice to know what they are also.

Virtually anything you find in the /proc/sys directory can be
manipulated using sysctl.  Find a parameter you want to change in
/proc/sys and put it in the /etc/sysctl.conf file.  The format of that
file uses "." characters in place of the "/" used in the /proc/sys
directory tree and assumes the ".proc.sys" bit (don't include it).  The
best source for this information is in the files found in the
"/usr/share/doc/kernel-doc-`uname -r`/Documentation/sysctl" directory,
specifically kernel.txt, fs.txt and vm.txt.

Note, however, that the items you want in there have nothing to do with
sysctl, but are rather "ulimit" values (see "man bash" and look for the
"ulimit" command under "BUILTIN").  You can view the currently active
values by using "ulimit -a".  They must be set by the shell using the
ulimit command BEFORE launching the program that requires the new
settings, e.g.

	#!/bin/bash
	# We need lots of open files, so...
	ulimit -n unlimited
	/path/to/program/to/run

Note that "-n" is a suggestion.  The actual number of open files is
compiled into the kernel.

Oh, and please get your mail administrator to take that incredibly
stupid and unenforceable disclaimer off your mail messages.

<flame>
The simple fact that you're posting to a PUBLIC mailing list kind of
removes any pretense of confidentiality, doesn't it?  I also have much
better things to do than drop everything and contact the sender of an
erroneous message because _he_ screwed up the destination address.
</flame>

I know you're not to blame for it, but someone has to rein in these
idiotic, intrusive, micromanipulative lawyers!  Jeeze!
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-       "I'd explain it to you, but your brain might explode."       -
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