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| Newer page: | version 2 | Last edited on Friday, October 29, 2004 4:28:12 am | by StuartYeates | |
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-Small Memory mini-HOWTO
-!!!Small Memory mini-HOWTO
-!Todd Burgess
-
- tburgess@uoguelph
.ca
-
-
-
-2000-12-12
-
-
-__Revision History__Revision .12000-12-01Revised by: tb
-
-
-
-
-
-Describes how to run Linux on a system with a small amount of
-memory.
-
-
-
-
-
-----; __Table of Contents__; 1. Introduction; 2. Linux Kernel; 3. Virtual Consoles; 4. Daemons: ; 4.1. inetd; 4.2. lpd; 4.3. nfsd and mountd; 4.4. portmap; 4.5. sendmail; 4.6. others; 5. Conclusions----
-!!!1. Introduction
-
-Assuming buying more memory is out of the question there are many
-things you can do to tighten up memory usage in Linux.
-
-
-
-Many Linux distributions out of the box are quite bloated from a
-memory perspective. They run more services and offer more features than most of
-us will ever need. By removing many of these services you can free up several
-megabytes of real memory.
-
-
-
- My own system is a 486DX2-66 with 12MB of physical memory and 12MB
-of swap space. It has run Linux for the last 3 years quite happily, and
-hopefully it will run Linux for several more years. :)
-
-----
-!!!2. Linux Kernel
-
-All the Linux kernels which come with distributions are quite
-bloated and contain more features than any of us will ever need or use. If you
-have not re-compiled your own kernel, it is highly recommended that you do so.
-How to re-compile a kernel is beyond the scope of this document, but many
-excellent Linux books and guides cover this subject in intimate detail.
-
-
-
-If you do re-compile your kernel, remember to put in no more
-features than you need. For instance: how many of you include PLIP support in
-your kernel? How many of you who include it actually use it? Smaller kernels
-require less time to load, use less memory, and use less CPU cycles.
-
-
-
-Another thing is modules. I personally do not use them because I
-found them to be a cumbersome. If you use them and like them then they can help
-to relieve "kernel bloat."
-
-----
-!!!3. Virtual Consoles
-
-VCs are a great way to free up memory. Most Linux distributions run
-about 6 of them out of the box. On average running 6 VCs requires about 4MB of
-memory. Removing a couple of them can free up a couple MBs of memory. Most
-users can get away with running only 3 or 4 VCs. How many you choose to remove
-is a matter personal preference. Just remember that the fewer you run, the more
-memory your applications will have to run.
-
-
-
-The file which outlines how many VCs get loaded is
-/etc/inittab. In order to remove VCs:
-
-
-
-
-
-
-#
-
-Load /etc/inittab in a text
-editor.
-
-
-#
-#
-
-Look for a line which looks like the following line (the key
-feature being a line which starts with c1):
-
-
-c1:12345:respawn:/sbin/getty tty1 38400
-linux
-
-Start at the highest number (i.e. c6) and comment it out by
-inserting a '#' in the first row. Repeat this step as many times as needed.
-Remember every line you comment out is one less VC running.
-
-
-#
-#
-
-Re-boot the system for your changes to take effect.
-
-
-#----
-!!!4. Daemons
-
-Many Linux distributions run daemons most of us will never use.
-Most of these daemons are loaded by scripts. Where these scripts are and what
-they are called depends on your Linux distribution. Slackware set-up scripts
-are buried in /etc/rc.d/rc.*.
-
-
-
-Before you proceed, a knowledge of Unix shell script programming
-would be a definite asset. However, if you have no experience writing Unix
-shell scripts, what follows is probably the quickest introduction to shell
-script programming ever written.
-
-
-
-Take the following shell script:
-
-
-#!/bin/sh echo "hello world"
-#echo "good bye cruel world"
-
-The previous code will echo the string "hello world". Shell scripts
-must contain the the line
-
-"#!/bin/sh" at the very top line.
-After that every line is executed as if you had typed it at the keyboard (think
-of shell scripts as nothing more then glorified keyboard macros).
-
-
-
-Lines which begin with a '#' are said to be commented out because
-they do not get executed by the shell. Most start-up scripts when they load
-daemons look like:
-
-
-if somecondition
-do something
-fi
-
-What you want to do is comment out every line starting with the
-if
-statement and ending with the
-fi statement.
-
-
-
-If you want to find where a daemon is loaded,
-search the start-up scripts for the name of the daemon. If I wanted to find
-where inetd is loaded in Slackware I would do the following:
-
-$ cd /edt/rc/d $grep -n inetd rd.*
-
-----
-!!4.1. inetd
-
-inetd allows people to do things like __telnet__, __ftp__, and send __talk__
-requests to your machine. If you never use your system as a server or need to
-access any of its services remotely you can remove inetd.
-
-----
-!!4.2. lpd
-
-lpd is used to print files on your printer using the
-__lpr__ command. If you never print on your Linux
-box you can remove lpd. If, however, you own a HP Deskjet (tm) printer and
-would like to print, I highly recommend the package I put together called
-dj-printcap which is available at:
-
-
-
-
-ftp://sunsite.unc.edu/pub/Linux/system/Printing/dj-printcap.tar.gz
-
-
-----
-!!4.3. nfsd and mountd
-
-These two daemons are used to run an NFS server. If you never use
-your Linux system as an NFS server you can safely remove these two daemons.
-
-
-----
-!!4.4. portmap
-
-The portmap daemon is used to handle RPC services. If you do not
-run an NFS server or any other RPC programs you can remove portmap.
-
-----
-!!4.5. sendmail
-
-sendmail is another daemon which requires a fair bit of memory.
-If you never use your Linux box as a relay for sending e-mail or you never
-receive mail on your Linux box, you can probably remove sendmail. If you do send
-e-mail from your Linux box most e-mail clients can be set-up to send e-mail
-from another mail server.
-
-----
-!!4.6. others
-
-There may be other daemons your system starts up which you do
-not need. Remove what you feel you have to. Two daemons which you must run are
-syslogd and klogd.
-
-----
-!!!5. Conclusions
-
-The previous discussion illustrates the steps I took to tighten up
-my memory usage on my Linux box. Hopefully I have provided you with some
-insight into what you can do with your Linux box to conserve memory. Good luck
-and happy hacking!
+Describe [HowToSmallMemory] here
.
