Tuning Linux System Parameters w/o Kernel Recompiles?

kernelInit.D asks: "I love Linux, but there is no way I am going to get the DBA's excited about having to recompile the kernel to install Oracle. Why can't Linux have something like Solaris's /etc/system file, where I can tune the OS without going through the hassle of hunting through source to make performance changes?" This is a good point, there are several parameters in the Linux config which could be moved to a file which the kernel consults at boot time. Are there technical or design limitations that have prevented its implementation?

Nice set of intro articles written on this

[hubie]

Marcel Gagne has written a nice series of intro articles on this topic for The Linux Journal [linuxjournal.com]. You can find the articles, called Tweaking Tux at LJ under the System Administration section in the archives [linuxjournal.com] section, or listed on his personal page [salmar.com] of his company's website [salmar.com].

Re:Probably slightly offtopic, but... AIX?

[joekool]

well, since AIX, and most other unixes(such as HP UNIX, etc), do not have source available, the only way to change a parameter is to have a tool to do it!

/proc/sys and Modules

[jfunk]

The /proc/sys directory and the modules are intended for exactly this. There is a nice hierarchial structure in /proc/sys that allows you to change many parameters on the fly. You can put echo <whatever> > /proc/sys/<whatever> in init scripts to set many parameters.

For the modules, you can add stuff to /etc/conf.modules to load modules as they are needed.

This stuff is very well documented, take a look around.

Can't do it

[lordpez]

The kernel doesn't mount the filesystem until its almost done booting, so it can't read a config file until its too late. As previously suggested, lilo mapping a config file into the boot record would be possible, but then you have to worry about limitation of the PC architecture when it comes to the size of the boot record. This prompts for the use of dynamic changes, such as the facilities provided by /proc.

Probably slightly offtopic, but... AIX?

[StandardDeviant]

I was reading Aelieen Frisch's _Essential System Administration_ (2e) last night and ran across the tidbit that AIX systems have no need of kernel recompilation becuase literally everything can be reconfiured on the fly with CLI commands (analogous to sysctl or something, but applying to everything). Of course AIX only runs on IBM hardware to my knowledge so the kernel team for AIX has a much more limited set of hardware to accomodate than linux does. (Don't take this as a recommendation of AIX per sé, I have no hands-on experience with it.)

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Re:Who says you need to recompile?

[Fjord]

We've had trouble loading in on RH7, though, so be warned.

Who says you need to recompile?

[sighup]

Oracle worked pretty much out of the box on our relatively stock Red Hat 6.2 boxes.

I only made one change. Add this to /etc/rc.d/rc.local:
# Increase system-wide file descriptor limit.
echo 8192 > /proc/sys/fs/file-max
echo 24576 > /proc/sys/fs/inode-max