How do I get the kernel source code?

Question

I am planning to write some device drivers and I need to get the Linux kernel source. My Linux kernel version is 3.2.0-23-generic-pae and I downloaded the image from this. In many of the articles I have read, it tells me that I need to have the entire kernel tree to start inserting new modules.

Is it enough if I download this image and paste it into the usr/src/ folder or do I have to do something else?

Answer 1

This will get the source of the stock kernel:

apt-get source linux-source

• https://help.ubuntu.com/community/Kernel/Compile/

You can check what version of the kernel is running like this:

uname -r

Which will print something like:

3.13.0-46-generic

You can find a list of current source package versions available on your system via:

apt-cache search linux-source

To get the upstream version of the kernel:

git clone git://kernel.ubuntu.com/ubuntu/ubuntu-trusty.git

• https://wiki.ubuntu.com/KernelTeam/GitKernelBuild

In the above link, 'trusty' is the codename for the version of Ubuntu. You can find out the codename for the version of Ubuntu you have installed via:

cat /etc/lsb-release

Answer 2

apt-get source linux

is the easiest way. It will download the source from your repository - and it'll be the same as the version you're running (assuming you haven't already customised it).

But if you want to find where the source is maintained you can run:

apt-cache showsrc linux

Look for the 'Vcs-' attribute (Version control system). It'll usually be a git (Vcs-Git) or mercurial repository.

Note - these commands work with any package. Just substitute 'linux' with the package you're interested in. And also note that 'apt-get source' doesn't need sudo access and will dump the source in your current directory.

Answer 3

Download source directly from Launchpad

Strangely enough everyone recommends apt-get source which doesn't work most of the time if you're looking for a specific kernel version:

Say you need kernel source for 3.19.0-58 :
apt-get source linux-image-3.19.0-58-generic will get the source for the latest kernel in the series: 3.19.0-80 in this case, which is not what you asked for.

So you have two options:

1) Give up, install kernel 3.19.0-80 and use apt-get source

2) Get source directly from launchpad:

• Google site:launchpad.net "linux-image-3.19.0-58-generic"

• That should give you the Launchpad Package Page for that version.

• Scroll down, click the "Source:" link, you're on the Package Source Page now.

• Scroll down and download .tar.gz, .diff.gz, .dsc files:

• Put them in a new directory, unpack with dpkg-source -x *.dsc

Notes:

• There must be a better way.
• You can get the version you want from git, but you're in for a big download. See "Obtaining the kernel sources for an Ubuntu release using git" in Ubuntu Wiki Kernel Source Code.

Answer 4

Just pick one from:

sudo apt install linux-source  # downloads into system directory
sudo apt source linux-source  # downloads into working directory

If you're told to give some 'sources' URLs in your sources.list, go edit your /etc/apt/sources.list file and uncomment the desired deb-src line, for example (if you're running Xenial):

deb http://fr.archive.ubuntu.com/ubuntu/ xenial main restricted
# deb-src http://fr.archive.ubuntu.com/ubuntu/ xenial main restricted

Removing the # on this last line enables sources repositories for download, including kernel sources.

Remarks:

• Use modern tools; avoid apt-get.
• These commands download the source code for your current kernel (in my case 4.4.0-75-generic for example).
• When downloaded into system directory, files are stored in /usr/src/linux-source-4.4.0/ (for example).

Answer 5

There are cases where it is simply more practical to download the linux kernel source and headers for the version you're interested in directly from http://kernel.org (a pretty reliable URL/site that isn't going away [e.g. standard stackoverflow concern about stale links isn't not an issue])

Reason? For example, you might be interested in debugging an older/defunct no-longer-supported version of linux where package repository points to dead areas, where in some cases there are either no viable current alternatives, or the repos has are expired keys that won't let you get the stuff, requiring unmemorable difficult to search out arcane techniques to get those repositories to work anyway.

Or maybe Internet networking might be broken on Linux machine (or VM) you're using, but file sharing or NFS works, where the source can be downloaded onto another machine and accessed via the filesystem.

If you're working with a relatively obsolete version of Linux, chances are you'll have to build a number of things from source and get them the hard way.