How to Create a Very Small Linux System Using Buildroot _ Agent OSS

How to create a very small Linux system using Buildroot | Agent OSS

http://agentoss.wordpress.com/2011/02/27/how-to-create-a-very-small-linux-system-using-buildroot/[23/7/2013 14:30:39]

Agent OSSOpen Source Software tutorials and reviews

Home About

How to create a very small Linux systemusing BuildrootPosted on 27/02/2011 by AgentOss

2 Votes

Have you ever tried to install amodern Linux distro onto asmall capacity (usually 32megs or even less) usb driveor compact flash card?Even with a minimal install, such a distribution will not fit! Major Linux distros likeDebian/Slackware/Arch/etc need a bare minimum of 300-400 megs of disk space.

The only minimal system I have been able to install so far on a 128Meg disk is NetBSD (http://www.netbsd.org ).

But there is a way to achieve such a thing : we will be using Buildroot in order to generate a Follow



very small (embedded) Linux system (targeted at a standard intel x86 computer)

In this tutorial I have used a Ubuntu 10.04 system as my build machine.

Buildroot :

http://buildroot.uclibc.org/

Documentation :

http://buildroot.uclibc.org/buildroot.html

Prior to using it, youll have to install a development environment on your system (GCCcompiler, Linux kernel headers, make tools etc). On Debian/Ubuntu, this is done byinstalling packages such as :

build-essentials

First of all, we need to download and setup Buildroot on our build machine.

As a standard user (not root) :

# cd

# wget http://buildroot.uclibc.org/downloads/buildroot-snapshot.tar.bz2

# tar xvjf buildroot*

# cd buildroot

Buildroot Configuration

# make menuconfig

Now you have to select some options :

My target architecture is an x86 system, optimized for Pentium (i686). But your mileage mayvary

Target Architecture : i386

Follow Agent OSSGet every new post deliveredto your Inbox.

Powered by WordPress.com



Target Architecture Variant : i686

Toolchain >[X] Enable large file

System Configuration >System hostname : choose your system nameSystem banner : anything you want[X] Generic serial port config (can be useful)

Update 01-07-2012 :

Now you need to set

Port to run a getty (login prompt) on to tty1 instead of ttyS0, in order to get a login promptwhen booting your generated system!

Package Selection for the target

We select here the software packages we want to be in our embedded system

[X] Show packages that are also provided by busybox[X] Customize

In this example I chose the following :

- support for foreign keyboard layouts

Hardware handling >[X] kbd

- optional, but can be useful

[X] makedevs



- some lightweight networking apps : dropbear (SSH server) , thttpd (ultra small http server)

Networking applications >[X] dropbear

[X] thttpd

- I like the nano text editor too

Text editors and viewers >

[X] nano

Target filesystem options >[X] initramfs for initial ramdisk of linux kernel

Uncheck the other options.

This way, our system files (rootfs) will be contained within the kernel file, and loaded intoRAM by the kernel.

(note : cramfs does the same, but is older and limited to a 16Meg rootfs max.)

Bootloaders >

Uncheck everything here. We will test our image using qemu so we dont need a bootloaderyet. If you want to put your embedded system on a bootable USB drive, you can useSYSLINUX/EXTLINUX to make it bootable (see here!).

Kernel >[X] Linux Kernel

Important :

in Defconfig name, enter the value : i386

it corresponds to the linux-2.6.37/arch/x86/configs/i386_defconfig file



(otherwise the build system will complain that it couldnt find a kernel configuration file).

Now select Exit to end the Buildroot configuration, save the changes of course (Thesesettings are stored in the .config file in the Buildroot directory).

Its time to start compiling!

# make

The first compilation will take some time, as software packages for the toolchain and othercomponents are downloaded, extracted and compiled on your build machine!

TIP :

If you need to configure the linux kernel for your special needs (youll likely have to) :# make linux-menuconfig

Important especially : remember to include support for the EXT2 filesystem in your kernel, ifyou want to be able to mount EXT2 formatted devices (usb flash drive for example) fromyour embedded system!

If everything went well, the compilation is finished and your final system files (kernel andoptional boot and rootfs files) will be found in the output/images sub-directory of yourBuildroot.

In our example, we can see that the obtained kernel file : bzImage, is very small (above 5megs, with and LZMA compressed initramfs filesystem)!

TIP

To force the complete rebuild of your embedded system :# rm -rf output/build

# make

Testing our embedded system

We can use the QEMU emulator on our build host to do so.



# apt-get install qemu

# qemu -kernel output/images/bzImageThe default root login (as generated by Buildroot) has no password. There also exists astandard user named default (no password too).

login: rootpassword: (none)

Now you can play with your lightweight (yet somewhat limited) sytem :

in order to start the network interface :

# ifconfig eth0

# udhcpc eth0

look at the busybox available commands :

# busybox

TIP

load a keymap :# loadkeys fr

Ok, we have a new system, but some things have to be improved in order to make it moreusable. We are going to apply changes to the root filesystem (rootfs) before its included inthe kernel by Buildroots make process.

Wed like, amongst other things :- that our preferred keymap be automatically loaded,- the network to be automatically up and running,etc

To do that, changes will be applied in the rootfs files contained in Buildroots output/target



subdir.

For the keymap :

# cd output/target

# nano etc/init.d/S99keymap

- file S99keymap #!/bin/sh

loadkeys fr- file S99keymap

# chmod 755 etc/init.d/S99keymap

AN ALTERNATIVE WAY TO DO THIS WITH BUSYBOX! :

BusyBox has internal keymap manipulation commands# dumpkmap >etc/french.kmap

# loadkmap fr.kmap

# cp fr.kmap output/target/etc/

and then the S99keymap file contains the following line instead :loadkmap



iface lo inet loopback

# automatically start eth0, with dhcpauto eth0iface eth0 inet dhcp-

While we are at it, we can modify the etc/TZ file, in order to have the correct timezone in ourembedded system.

Hare the TZ value below corresponds to Europe/Paris, see here for your preferred value :http://www.sonoracomm.com/support/20-voice-support/107-uclibc-tz

# echo "CET-1CEST-2,M3.5.0/02:00:00,M10.5.0/03:00:00" >etc/TZ

SECURITY enhancements :

- Change the root password :

There maybe other ways to do the trick, but I found this one to be working :

# apt-get install mkpasswd

# echo 'mynewpassword' | mkpasswd -s -m md5

then paste the obtained string : $1$2VnNG40d$3SSSNXs.FfPnzlx9CMHZE/ (you willobtain another value, this is just an example)in the output/target/etc/shadow file, like this :

-etc/shadow -root:$1$2VnNG40d$3SSSNXs.FfPnzlx9CMHZE/:10933:0:99999:7:::

Lets de-activate the default user login too :

modify the line :

default::10933:0:99999:7:::

into :



default:LK:10933:0:99999:7:::

(LK is for locked)

Other modifications (may be useful, some more testing needed!) :

To improve device hotplug support, add the two following lines

null::sysinit:/bin/echo /sbin/mdev >/proc/sys/kernel/hotplugnull::sysinit:/sbin/mdev -s

in the output/target/etc/inittab file. So that it looks :

etc/inittab # Startup the systemnull::sysinit:/bin/mount -t proc proc /procnull::sysinit:/bin/mount -o remount,rw /null::sysinit:/bin/mkdir -p /dev/ptsnull::sysinit:/bin/echo /sbin/mdev >/proc/sys/kernel/hotplugnull::sysinit:/sbin/mdev -snull::sysinit:/bin/mount -anull::sysinit:/bin/hostname -F /etc/hostname etc/inittab

Final generation of our embedded Linux system :

go back to the Buildroot directory, then

# make

TIP :

If you delete the whole output subir, your changes in the output/target rootfs will be lost(obviously!) so it may be more convenient to make your changes in the fs/skeleton subdir,so that they will be used when generating the target subdir.



How to create a bootable Linux USB drive

using EXTLINUX

26 thoughts on How to create a very small Linux systemusing Buildroot

Share this:

Like this:

Be the first to like this.

Like

There is still plenty of work to do in our embedded system, but youve got the processuncovered.

This entry was posted in Howto, Linux and tagged buildroot, embedded, lightweight, linux, smallest, system, tiny.

Bookmark the permalink.

by Gravity

Is This The Easiest GolfSwing EVER?

Titans fan who went viralgets showered with gifts

Actress loses lawsuitagainst IMDB for

If You Want To BeAwesome At Emails, Add

About these ads

Email Print Digg Facebook Reddit StumbleUpon Twitter

venkat says:

18/08/2011 at 00:45

hi,



I followed your procedure, but i am getting kernel panic when I emulate using qemu.

please help me. what is your build environment?

Cheers,Venkat

Reply

AgentOss says:

18/08/2011 at 10:49

Hi

Im using a Debian 6.0 virtual machine (VirtualBox) for my buildroot environment.

Try starting qemu with -m 256 (to emulate 256Megs of RAM). By default qemuuses 128Megs, which might not be nough for bigger kernels.

If that doesnt still work, please show a screen capture and your qemu line

Reply

venkat says:

18/08/2011 at 11:43

Thank you so much for the response. I shall try that and I get back to you .

Cheers,Venkat

Reply



David J says:

07/01/2012 at 07:08

Hi,I followed your steps, but in the end the qemu hangs on starting tftpd.. After googling,it seems it didnt start console on serial port, but I cant figure out what is the next. Theinittab looks have the right ttyS0:

# Put a getty on the serial portttyS0::respawn:/sbin/getty -L ttyS0 38400 vt100 # GENERIC_SERIAL

Can you help?

Reply

AgentOss says:

07/01/2012 at 13:31

Hi,

Looks like that we need to use tty1 instead of ttyS0 !

Then youll have a login prompt in your buildroot system.

Im updating this howto

Thanks & have fun!

Reply

David J says:

07/01/2012 at 17:41

Its working perfectly. This will be my starting point and look forward to reducing thememory consumption. Do you have any suggestion or link?



Thanks and have a great day!

DJ

Reply

AgentOss says:

07/01/2012 at 22:17

Good!

What are your memory requirements?

You could configure the kernel to remove unneeded drivers and features, but thiswont give a big gain in memory consumption.

I found that a minimal buildroot generated system (no X) with initramfs embeddedwithin the kernel needs at least 27M of RAM to boot, not less.

If you have less RAM, you might try to generate a kernel with no embeddedinitramfs, but then you need to create a virtual hard disk with the root filesystem onit (when using qemu).

Reply

David J says:

08/01/2012 at 07:07

Thanks for reply.I try to get down to 10M. Generating a kernel without initramfs seems a goodoption. How to create virtual disk with qemu? Thanks again.

AgentOss says:



08/01/2012 at 21:00

In Buildroot > Filesystem Images menu :

- uncheck initramfs- check ext2 root filesystem

Then boot the system with :

qemu -kernel bzImage -append root=/dev/sda -hda rootfs.ext2

And remember to include support for ext2 fs in the kernel (not as module), otherwisethe kernel wont be able to mount the rootfs.

Still cant boot with less than 24Mb of RAM!

This is because the kernel needs this to decompress itself. We could try with anuncompressed kernel (but so far I dont know how to obtain it)

Or you may try with an older 2.6.27.58 kernel, with it I could boot on a 16Mb system!

Reply

stewe says:

05/02/2012 at 21:12

hi

how it is possible that you have eth0 device present in the system? I do it by virtualboxand there is only lo device and sit0, i do the same with qemu but theres no eth0 at all what should i do in order to setup networking? thx

Reply



AgentOss says:

05/02/2012 at 21:29

Hi,

Have you configured your kernel with the ethernet drivers? (include them all indoubt)

Also, paste your dmesg to pastebin and give us the link here so we can see whatshappening

Reply

stewe says:

05/02/2012 at 23:44

ive got it, i had to compile some additional network driver to the kernel(Intel(R) 82575/82576 PCI-Express Gigabit Ethernet support + Intel(R) 82576Virtual Function Ethernet support) and switch network adapter in vmwaresetting like Intel PRO/1000 MT Desktop (82540EM) under network adapter 1 advanced settings

Peter says:

18/01/2013 at 16:05

I tried to preapre my own linux by buildroot but after changed of ttyS0 to ttyS1 I stillcannot see login promt, it hangs after dropbear dsa key generated. I didnt add thttpd. Ihave tried to change baudrate and ttyS to higher but after two days of compiling mykernel still hangs after dropbear

Reply

AgentOss says:

18/01/2013 at 18:08



It should be tty1, not ttyS1 (S is for serial port)

Reply

Peter says:

18/01/2013 at 18:33

OMG, you are a GOD, what a stupid mistake.

Thank You!

Reply

Antoine says:

12/02/2013 at 15:38

Hi, I tried your tutorial, but buildroot fails at building host-m4 :make[1]: Entering directory `/home/antoine/buildroot-2012.11.1/output/build/host-m4-1.4.16

make[1]: warning: -jN forced in submake: disabling jobserver mode.make[1]: *** INTERNAL: readdir: Not a directory. Stop.make[1]: maint.mk: Field stem not cached: maint.mk

make[1]: Leaving directory `/home/antoine/buildroot-2012.11.1/output/build/host-m4-1.4.16

I tried to use google, but I could not figure out what was wrong

Reply



AgentOss says:

12/02/2013 at 18:03

Hi, sorry I dont know about that.

The best thing to do would be to ask in the official Buildroot mailing lists!

Reply

xsmos says:

18/02/2013 at 18:47

I said I followed your tutorial to the letter but the launch of the initramfs image with thelaunch qemu hangs a thttpd server initializationmy config is as followsLubuntu 12.04 X64Intel core I36 giga ramplease help me thank you

Reply

AgentOss says:

18/02/2013 at 19:01

maybe a problem with tty1 not enabled (see the other comments above)

Reply

Peter says:

03/03/2013 at 12:31

Hi,



How can I build a system with buildroot which will be remember changes which I madeon harddrive? So it will remember changes which I made in rootfs.cpio filesystem, or itwill remember that Ive added some new software.

Regards,Piotr

Reply

AgentOss says:

03/03/2013 at 14:31

Hi, I havent experimented that kind of things yet But look at Slitaz, or even Slax.They have different mechanisms to do what you are looking for

Reply

Albert says:

06/04/2013 at 09:17

after the configuration and when i excute the make command i get this error message:

2013-04-06 08:12:51 http://ftp.gnu.org/pub/gnu/gmp/gmp-5.0.2.tar.bz2Connecting to 192.168.110.80:8080 failed: Connection timed out.Retrying.

2013-04-06 08:13:13 (try: 2) http://ftp.gnu.org/pub/gnu/gmp/gmp-5.0.2.tar.bz2Connecting to 192.168.110.80:8080 failed: Connection timed out.Retrying.

2013-04-06 08:13:36 (try: 3) http://ftp.gnu.org/pub/gnu/gmp/gmp-5.0.2.tar.bz2Connecting to 192.168.110.80:8080 failed: Connection timed out.Giving up.



2013-04-06 08:13:57 http://sources.buildroot.net//gmp-5.0.2.tar.bz2Connecting to 192.168.110.80:8080 failed: Connection timed out.Retrying.

2013-04-06 08:14:19 (try: 2) http://sources.buildroot.net//gmp-5.0.2.tar.bz2Connecting to 192.168.110.80:8080 failed: Connection timed out.Retrying.

2013-04-06 08:14:42 (try: 3) http://sources.buildroot.net//gmp-5.0.2.tar.bz2Connecting to 192.168.110.80:8080 failed: Connection timed out.Giving up.

Reply

AgentOss says:

06/04/2013 at 12:21

It looks like you are behind a proxy that prevents you from downloading Check your network / ask your sysadmin!

Reply

Albert says:

06/04/2013 at 22:21

when i excute:# qemu -kernel output/images/bzImage

i get this message :

pci_add_option_rom: failed to find romfile pxe-rtl8139.bin

Reply



Recent Posts

Wifi repeater/range extender script

Debian 6.0 (Squeeze) on the Xplore iX104C3 rugged Tablet PC

Debian Wheezy and systemd

Home mail server with Postfix + Dovecot (IMAP) + Squirrelmail/Roundcube on NetBSD 6.0.1

Wireless Ad-hoc server script

Leave a Reply

Alfred says:

10/04/2013 at 09:26

when i excute ifconfig eth0ifconfig eth0 error fetching interface information device not found

Reply

AgentOss says:

10/04/2013 at 18:23

Maybe your ethernet driver (module) is missing. Verify that you have it in yourkernel config.

Reply

Enter your comment here...



Categories

Arch

Bash scripts

BSD

Debian

Howto

Linux

Mageia

Tags

Archives

Select Month

Links

BSD Guides

Distrowatch

HowtoForge

LinuxQuestions

Mageia Linux

nixCraft

3130 access point AMD apache arch backtrack bootable bootloader brazos bridge buildroot busybox

compact flash compilation configuration crux debian desktop distro DM1 drive e-350 embeddedextlinux fast boot fedora fglrx g4 hardware hibernation hotspot ibm imac g3 install KDE kernel laptoplightweight linux macintosh mageia mandriva mp3 netbook netboot netinstall old computer openbsdopensuse package manager pclinuxos player ports powermac powerpc recycled review server simple

smallest sony vaio syslinux system thinkpad 365x tiny touchpad ubuntu usb wifi windows wireless x xfcexorg zacate



February 2011

M T W T F S S

Mar

1 2 3 4 5 6

7 8 9 10 11 12 13

14 15 16 17 18 19 20

21 22 23 24 25 2627

28

Enter your email address to follow this blog and receive notifications of new posts by email.

Join 15 other followers

Follow Blog via Email

RSS

RSS - Posts

RSS - Comments



Blog at WordPress.com. | The Able Theme.

wordpress.comHow to create a very small Linux system using Buildroot | Agent OSS

N0ZW0tdXNpbmctYnVpbGRyb290LwA=: form3: email: Enter your email addressinput0: comment:

N0ZW0tdXNpbmctYnVpbGRyb290LwA=: form0: s: submit:

N0ZW0tdXNpbmctYnVpbGRyb290LwA=: archive-dropdown:

N0ZW0tdXNpbmctYnVpbGRyb290LwA=: form2: email: input13:

How to Create a Very Small Linux System Using Buildroot _ Agent OSS

Documents

small embedded linux

x86 system

minimal system

buildroot agent osshttp

system gcccompiler

generated system

setup buildroot

system namesystem banner