Hi

For an embedded system I am working on (using a PC/104 module which is basically a stripped down PC), I need a linux distribution that can boot very quickly and has a read only filesystem. It needs to be read only so that when the user turns off power (without using shutdown -h now) there will be no problems with the system. There is actually no non-volatile storage on the board aside from flash memory which will be used to store the operating system.

Also, it preferably should have x window system (or the capability for me to add it as a package) with some graphics hardware acceleration so that I can run an opengl graphical program over the top of it. Does anyone have any ideas? Most of those requirements are probably ok but the fast boot time one really makes my decision harder without having the experience of using these distributions in the past...

Any help appreciated, thanks.

I don't know how 'embedded' you're going here, but KNOPPIX sounds like it would fit your bill.

Try this link-it's a slow download HTTP, maybe try bittorrent?
Make sure you read about the cheatcode for ENGLISH!

http://www.alpha.co.jp/biz/rdg/ac-knoppix/index_en.html

Knoppix is a good choice due to it's excellent support for all kinds of hardware. Unfortunately it's also quite bloated with software (it has to be, it is meant to be the swiss army knife among the Linux distro's), so you would have remove a lot of packages to create your own custom version of Knoppix. Knoppix is quite flexible and has good documentation on all technical topics.

But if you do not not want ending up spending a lot of time by reassembling Knoppix, you could also try DSL (Damn Small Linux - http://damnsmalllinux.org/). A core DSL installation takes 50 MB, so it's fits neatly on older USB sticks, it can also boot from within another OS (usually Windows). It supports X11 with some lightweight window manager. This could be more of an out-of-the-box solution for an embedded computer.

linux

Fedora Live CDs are much slower than Fedora, but you can make custom spins very easily. All you need to do is to edit /write a kickstart file ...

I think the previous posters didn't pay attention to your question & the hardware your using. You need a fast X windows environment with X. I would suggest Damn Small Linux & Parted Magic. (Which BTW I am using now to edit my partitions.) Both very light weight and have all the necessary tools for networking and harware.

Parted Magic

Damn Small Linux


Hope this helps...

And set the boot parameters for a read only FS.


EDIT:
Might be easier to just build a custom gentoo build, with a minimal X. Like flux, or JWM. And then create an install cd for your new build. If you have a network, you can always distcc your builds, and your compile times would be minimal. Or even go with a OpenVZ solution If you have multiple nodes, super fast. I'd have all your nodes PXE boot off the server.

KT

Thanks for the help everyone. I had already tried DamnSmallLinux but it is based on the 2.4 kernel and doesn't have support for the onboard NIC which I couldn't find a driver for..

I want to give Knoppix and Fedora a try but they are 700MB images.. ie. huge. Accelerated Knoppix looks interesting but it seems to be accelerated by optimising the seek times of a CD - I will actually be booting from flash ROM so will not see an improvement in speed.

I will keep searching but I appreciate everyone's help.

EDIT: sorry manwithaplan, I missed your edit. Are you saying that making a partition readonly is all I need to do? Do you mean choose squashfs or similar, or can I set a standard ext2/3 partition to readonly too? Does this cause any problems with a standard installed linux? Can I set it to read only after I have installed linux (otherwise it wouldn't install obviously!)

Yes... you could create a squashfs, or cramfs install. This would be ideal, and you could do it with a chroot install. First creating a squashfs file, mount it, and chroot a gentoo install, and make it lightweight. Then load grub to your ROM or FLASH device and pass the boot arguments through grub. e.g. Like when you copy a Livecd squashfs files to a hdd partiton and load from grub. I do this with a Sabayon Livecd on one of my HDD partitions. Totally read only... unless I specify differently.

As for a standard ext partitions, you can make them read only through a fstab entry. After an install of course. You can even specify the umask, gid values to prevent any access to the partitions. Completely customizable.


BTW, whats the disk size your using for an install? I have an idea...

Wow, those instructions are GOLD to me, thanks for that!

In terms of size of the flash disk, I can go anywhere from 128MB to 1GB modules.. obviously bigger size == more expensive so I was hoping I could do, say, a fedora install and then remove all the bloat packages to as low as possible.

My idea .. was to choose whatever livecd distro you want, and copy the squashfs file to your 1GB module. Then load grub on the module and pass the arguments through grub to boot the squashfs file, of any distro you want. I would go with the smallest file size... because it does expand and uses ram.

e.g. The !#Crunchbang distro has a squashfs file size of 678MB. You'd have to test which distro you prefer, and check with there documentation or there user forums to boot the file image. Its pretty neat. I use my Livecd hdd partition for diags and tools, or to fix problems.

Though Sabayon's file size exceeds 1GB, here's an example of what I mean by loading a squashfile from hdd. BTW I also do this with System Rescue CD, and Clonzilla.

Here's the site for Sabayon's instructions as an example.

Here & Here

Glad I could help


EDIT: If you dont mind installing Fedora on a seperate machine, then remove all the bloat you dont want. There's a tool called Remastersys, that builds a custom Livecd (squashfs) with your current install. It saves all customizations, toolbars, applets, wallpaper... etc ...etc. This allows you to slim everything down. You then can boot off the image from grub... And the great thing is its all readonly... changes dont stay unless specified directly.

thanks mate, that's a great help. If that remastersys program saves literally everything (apps, scripts etc) then I'm definitely going to research that more. but does squashfs compress files by much? it may be wiser for me to just mount an ext partition as readonly, saving step of having to use remastersys.

Remastersys, does compress considerably. It takes an actual snapshot of your current install, scripts, filesystem and configuration you currently have installed and configured. (Really nice for custom live disks).

I used to use the program to create an Ubuntu LiveDVD with a bunch of tools for a rescue disk. I removed all the stuff I didnt need. And loaded all the programs I did need, for a tech disk. Though it did exceed 700mb. So I burned it to a DVD.

Then I just started to use my new hi-speed USB to save from burning DVD's. I had enough space so I stopped making my liveDVD's and just downloaded complete Live disks and loaded grub to my USB and booted the different tools I needed. Very handy.

Though in your case its different. You need minimum. So, I recommend installing Fedora onto a regular PC and slim it down... as much as possible. Don't worry, using Remastersys saves all changes, then squashes the filesystem and creates a bootable image (iso). You might have to run Remastersys a couple of times to get it to the right size you want... I guess if you thinned it out, you could get it around 400-600MB iso, maybe smaller... FYI I've never tried this with Fedora.

After you've created the .iso image, you can then mount the loop and extract the squashfile to your module. Then follow up with loading grub and configuring to boot the squashfile.

Here's info on the squashfs compression here

BTW, Fedora 11 is looking great.

I'm definitely going to do what you said, but I'm not sure about using squashfs because I just realised that there will be a slower boot time as the filesystem is uncompressed and unsquashed on boot.. if I want the fastest boot time, maybe I should keep it uncompressed and just mount a standard ext partition as readonly. Then it becomes a cost vs speed issue..
thanks for your help!