I'm working on a side project which requires me to configure and compile a tiny Linux System based on Ubuntu.
The result should be a tiny OS with the following features:
A Bootloader
A Kernel
A Process
A Thread
Miscellaneous (if possible)
A File System
Virtual memory
A Console
I read lots of documents about it, one of them being: http://users.cecs.anu.edu.au/~okeefe/p2b/buildMin/buildMin.html#toc3
I deleted the file system, and recompiled the kernel using make xconfig. I tried to deactivate modules and configurations many times, but it's not working for me.
How can I configure the kernel for the OS with only the features I listed above? What options can I disable or enable while still having a working system?
Having the Kernel very small is not important for Ubuntu, so maybe choosing Ubuntu is part of your problem. I would use as starting point what OpenWRT does. They do a good work making the Kernel small and it is easy to get started. OpenWrt Buildroot – Usage
try Linux From Scratch. It is a step by step approach on building a minimal Linux system from which you can evolve later on. http://www.linuxfromscratch.org/.
Use Gentoo Linux distribution - it's great for practicing on creation of Linux systems. Gentoo has excellent setup documentation, for example about configuring the kernel.
And Gentoo is a little easier and faster to setup than Linux From Scratch (LFS). If you want to go deeper, then LFS may be a good learning step too.
Related
I am trying to build minimal kernel under 1 Mb with Buildroot. It is intended for small board with qspi memory and basic functionality, ethernet, usb, spi, and some GPIO's. Basic terminal access via ssh and UART.
My first thoughts are if it is even possible to modify kernel .config via linux-menuconfig to reach this size.
Also if it is possible to identify the redundant parts without deep knowledge about kernel architecture and exclude them from compilation.
If someone can direct me to good direction how to solve this problem or even specify some tools and ways how to do it would be very helpful.
Thank you!
If you have working build root for your board, than, it's better to continue to work with it. Technic for disabling kernel options should be the same. In the article he reached ~0,7MB uImage with lost a lot of functionality (p40). He started with minimal (bare) config (p27) and add blocks of configs. So instead of identify the redundant parts you can build smallest possible uImage you can boot. Than add to it more options: ext2, serial and so on. Actually this work require a lot of testing. And you probably brake dependencies.
Kernel configs (working and new one) could be compared using diff -Naur, so you can see what changed.
Offtopic:
Looks like yocto officially supported by altera. here are instructions how to build altera-image-minimal. If you fine with it size, than use it and don't spend time on minimizing uImage. If you need extra packages installed into it, than you can ease extend it.
And here are instructions about building Angstrom (yocto based distribution). You can create you custom image based on console-image-minimal.
I use Angstrom in production. Must say, it was really hard to use it first time.
Whether or not you build the kernel with buildroot is not really relevant. The important thing is to configure it so it fits in 1MB. When you build the kernel from buildroot, you can do that with make linux-menuconfig, as you mention.
That said, getting a kernel under 1MB will be quite hard. Biff once did this for an x86-based platform, bifferboard. But that was without networking or USB.
You can refer to the kernel size tuning guide, which has links to some patches to reduce the size. But it's not been updated in a couple of years.
I am new to linux programming & interested to tweak linux kernel(though I am not sure, what to tweak, I am planning to write drivers for particular device). To learn internal of kernel, I have started from historic kernel release (first release).
My problem is, how to test whatever changes I am doing for development, without disturbing my current os environment.(ubuntu 12, 64 bit). Is there any way like virtual box, sandbox?
Along with these, if anybody send some good approaches to learn these things, I would be really greatful.
Thank You.
If you're new to linux programming then you really don't want to be tweaking the kernel. You really want to be an advanced programmer capable of programming drivers and complex software first.
But yes there is, you can can create a virtual machine using openbox or vmware. If you're really keen on tweaking the kernel you probably want to first just try compiling and configuring the kernel and seeing if that works.
Also make sure you're well acquainted with how the kernel works and advanced OS designs in general.
Search in google fr "Kernel configuration" you u will get many links how to configure your own kernel.
And one more thing do not use a outdated version of kernel ,always use latest stable release , because a lot of code and API is changed in new versions and no book in market is updated so ,, u have to read from kernel documentation. Thats the best way to learn the most updated information about linux kernel
Yes, you can test your changes on any of the commonly available virtual machines (VMs); that way, whatever changes you make to the VM kernel won't affect native OS.
Personally, I prefer using CentOS 64 bit on VMWare Player. With this setup, I got away with minimal system maintenance while was able to focus on the actual job at hand. Once the VM is up & running, you can download and compile one of the latest stable releases from kernel.org. Instructions on compiling your downloaded version of kernel could be found here and here; however, this may require little tweaking based on your actual setup. Once the VM is running on your desired version of kernel, using a combination of cscope and ctags will help you immensely in kernel code browsing.
Finally, if you want to become a serious kernel programmer and write your own device drivers, you need to get familiar with it in the first place. Below are a few excellent references -
Linux Device Driver by Corbet, Rubini, Kroah-Hartman, 3rd edition
Linux Kernel Development by Robert Love, 3rd edition
Understanding the Linux Kernel by Bovet, Cesati
Linux kernel source (ideally placed into your /usr/src/$(DESIRED_KERNEL) path, symlinked to /usr/src/linux)
Going through these books is a tedious job and chances are that you may hit the roadblock from time to time. kernelnewbies mailing list and StackOverflow are some of the few reliable places where people would be happy to answer to your queries.
Good luck!
I want to build a sample program and as an initial step to learn KVM I started it from the link below.
http://www.linuxjournal.com/magazine/linux-kvm-learning-tool?page=0,1
I see that this is quite an old post for KVM, but I realize that the very first program does not compiles as it asks to include libkvm.h, which is not in my Ubuntu 13.04 installation.
To prepare for this program I installed qemu-kvm,dkms and libvirt stuff.
I also verified that the user has kvm and libvirtd in the group.
I am running Ubuntu on virtual-box on a modern i7 processor windows host.
So I have two different questions here -
1) Since I dont find libkvm.h in my box, what is the way compile my program and learn this kind of programming. If you have any tutorials please forward.
2) I got know that there is another libkvm that is used in BSD style Unix (e.g NetBSD/FreeBSD) that is used to access kernel data-strucrtures. From internet I see that GDB uses that library to fetch info from kernel memory. KVM in linux is a tool to create virtual machines on a Linux box. Is my understanding correct or is there anything more to it? Please provide a comparative analysis between these two libraries, namely libkvm on linux and libkvm on BSD?
As you already said, Linux KVM is a virtualisation technique whereas BSD kvm is much older, the acronym even expands to something different, and is a library to access (not only) kernel data structures in a defined manner.
They are totally separate and different things that have absolutely nothing to do with each other except for sharing the same acronym.
As do, for example, Keyboard-Video-Mouse switches. I was confused by all those Linux people talking about a “KVM” thing suddenly, back when Linux-KVM first came out, and not meaning those.
I will have (maybe) to work soon on ARM platform hosting a linux distribution (I don't know which distribution ..).
I know the project concerns video streaming, but I can't tell you more. Actually I only received the announe, and meet nobody yet.
I've never worked on such platform. So the idea for me is to test before the project starts.
What would you advise me to undestand how works such platform ? Internet links? Tutorials? Tools
Morevover, as I don't have any ARM processor at home (well only my iPhone ..) Which virtual machine would you advise me? (I clearly don't want to lose time installing and testing every one of them.)
I am aware of this page on wikipedia. Which one is the more appropriate running on a MacOS X 10.5/intel platform? Which linux distribution to install on the virtual machine?
I know the topic is quite wide, so any idea is welcomed! :-)
For a virtual machine that can emulate a ARM platform try QEMU. You can install a ARM-based Debian Linux distribution and tinker around with it. A google search on ARM, QEMU and Debian will get you started.
Also: Don't worry to much about the ARM CPU. You will use linux, so all the low-level stuff is already done for you. It's much more important to learn how the linux boot process works. How to install stuff ect. You will rarely (if ever) notice that you're running on a ARM device. The big difference to a PC running linux is, that the ARM will be a lot slower.
If you're looking for a real piece of hardware to play around with I suggest that you take a look at the beagleboard (www.beagleboard.org). It's cheap (around $150) and runs (among other things) various linux distributions.
With the beagleboard you'll get the whole linux cross compilation experience if you want (be warned: you'll pull your hair out).
I can't answer all of your questions, but there's a full port of Debian GNU/Linux on ARM. Works fabulously in my experience (I've tried it on a QNAP). Everything that's available in Debian works on QNAP now! So it's probably easiest to first try Debian tools and packages that come close to your project, and then continue from there.
In my Operating Systems class we are looking to modify a Linux kernel with some simple system calls of our own in C.
What would be a good distro suited for this purpose? We don't need any frills, no GUI, a vanilla kernel, etc. The more basic the better.
I was able to modify the kernel pretty easily using a minimal Gentoo install.
Just install gentoo, follow the installation instructions, then:
$ emerge gentoo-sources
$ emerge emacs
$ cd /usr/src/linux
In my operating systems course last semester we used User Mode Linux, the big advantage being that when you hose the system, you can simply kill the process with no risk to the host environment.
Adding/Modifying system calls is tedious but trivial regardless of the kernel you use. However the 2.6 kernel is significantly more massive and complex, so if you're going to be modifying the code in a significant way the older kernels are easier to work with and much better documented. (ie: easier to find books and references)
Happy hacking :)
archlinux++
but really.. gentoo, slack, and arch are all more-or-less good choices
Arch Linux provides a great platform for kernel development that is also very functional. If you learn to use pacman, it will actually make testing your kernel modifications quite easily and provides the sources and tools in a sane manner.
I do think that if you are serious about learning linux and kernel hacking, doing a Linux From Scratch install should be on your list. It's a great distro/book and will let you build the platform for development yourself.
On all distributions, you can install the vanilla kernel.org sources instead of the distribution-related kernel packages, which is probably a good idea anyway when you want to do kernel development.
However, you'll be in trouble when you want to use any recent distribution with non-2.6 kernels, because they often build libc6 in a way that it cannot run with 2.4. Additionally, a lot of the guts of hardware management (like udev) require fairly recent kernels.
Apart from that, using Debian gives you a barebone system, and installing your own kernels is a breeze with kernel-package.
I wouldn't necessarily say any particular distro is geared towards kernel development as such, but if you want a traditional Linux distro that doesn't pile too much custom configuration stuff between you and the kernel, Slackware is a decent choice.
My suggestion is to grab the latest kernel. There will be more debugging features inside it than in an older kernel. Also, older kernels would pretty much look just as complex as the most recent to the newbie.
As for the distribution itself, you can't really go wrong. If all you want is to try some custom system calls, then grab whatever mainstream distribution which gives you a nice development environment. Then compile and try your customized glibc without installing it over the distro's.
When choosing a distro for kernel development, remember that it's the kernel you want to hack, not the distro itself. You will therefor want an easy distro that stays out of your way as much as possible. Ubuntu says out of the way fairly nicely.
IANAKH
A non-linux alternative is Geek OS, but this is very much aimed at the educational level, and is not a practical kernel. It is ultra-simple though.
well I have found one called "minix" it isn't really a linux distro, but it was made specifically for teaching, but if you can only use a linux distro, then it shouldn't matter, I am pretty sure all distros have the same kernel
Gentoo if you dont mind automated compilation (most people think that gentoo is Linux From Scratch => you have to do everything on your own).
Arch if you have slower computer (laptop).
Biggest advantage of these two is that they have very very good documentation and only installing Gentoo f.e. gives you basic knowledge about init system and what services has to run. If one copy&paste commands from guide it's worthless though (luckily handbook makes people think a bit, thus preventing kids from installing gentoo and taking over our neat #irc) :D