# Debian kernel packages

## Source packages

The `linux` source package supports building of kernel images and headers for all currently supported architectures. The `linux-latest` source package supports building of meta-packages that depend on them. The `linux-signed` source package supports building of signed kernel images and modules for some architectures. Subsequent sections of this chapter document the naming and contents of the binary packages built from these source packages.

## Architecture-independent packages

`linux-source-`version``

- This package contains the Debian kernel source tarball. The patchlevel of the source is determined by the Debian revision of the package, for example the version 4.2.5-1 of the package `linux-source-4.2` contains the version 4.2.5 of the Debian kernel source patched to patchlevel 1. Once the package is installed, the source tarball is available at `/usr/src/linux-source-`version`.tar.xz`.

`linux-manual-`version``

- This package contains the manual pages for the functions, constituting the kernel API. These pages are installed into `/usr/share/man/man9/`, and are accessible with the standard `man` command. Due to filename conflicts, only one `linux-manual` package may be installed at any given time.

`linux-doc-`version``

- This package contains the rest of the kernel documentation in various formats. It is installed in `/usr/share/doc/linux-doc-`version``.

`linux-support-`version`-`abiname``

- This package contains metadata from the `linux` source package that is needed to prepare and build the other source packages.

`linux-headers-`version`-`abiname`-common[-`featureset`]`

- This package contains a common set of kernel headers for a particular featureset (or no featureset). Together with the flavour-specific `linux-headers` package it provides a full set of kernel headers, suitable for building of out-of-tree modules. This package should not normally be installed directly, but only as a dependency of the flavour-specific headers package (see below). It unpacks into the `/usr/src/linux-headers-`version`-`abiname`-common[-`featureset`]` directory. Before version 4.9 these packages were architecture-dependent.

## Architecture-dependent packages

The kind of hardware the particular kernel package is designed for is uniquely identified by the architecture, featureset, and flavour. Kernels for all architectures are built from the same Debian kernel source tree, which is obtained using the procedure described in ch-source. Each architecture usually has multiple flavours of the binary kernel images. Different flavours correspond to different kernel configuration files, used to build the binary images from the same kernel tree.

In order to build a working kernel with an extra featureset not provided by the upstream source, additional changes to the Debian kernel source are required. Again, multiple flavours of binary images may be built from the featureset tree. For example, the `i386` architecture has a number of different flavours, such as `686` and `686-pae`, built from the common Debian kernel source. It also contains the `rt` featureset. The source tree for building the kernels for each of these featuresets is obtained by applying additional patches to the Debian kernel source. It may be used to build the `rt-686-pae` binary image flavours. The names of the Debian binary packages incorporate the name of the flavour and, if necessary, the name of the featureset (there is no need to worry about the name of the architecture, since Debian tools will only allow installation of the packages with "correct" architecture). If the arch does not have any featuresets, the featureset part is omitted from the name, as indicated by the square brackets below.

Package names also include the abiname, a small integer, which identifies the kernel's binary compatibility level. The kernels with different abinames are binary incompatible, so upgrading to a kernel with a different abiname will most likely require recompilation of third-party binary modules against the new kernel. The list of architecture-dependent packages together with a short description is given below.

`linux-headers-`version`-`abiname`[-`featureset`]-`flavour``

- This package provides flavour-specific header files. It depends on the corresponding `linux-headers-`version`-`abiname`-common[-`featureset`]` package, and sets up symbolic links into its directory tree in such a way that the directory `/usr/src/linux-headers-`version`-`abiname`[-`featureset`]-`flavour`` appears to contain a full set of headers, required for building of out-of-tree kernel modules. For more information on this check out s-common-out-of-tree. A complete set of kernel headers matching the currently running official kernel may be installed with a command

      apt-get install linux-headers-$(uname -r)

`linux-image[-`featureset`]-`flavour``

`linux-headers[-`featureset`]-`flavour``

- These meta-packages provide (via dependencies) the latest binary image and matching set of header files (respectively) for a particular flavour. Example: `linux-image-rt-686-pae`

`linux-image-`version`-`abiname`[-`featureset`]-`flavour``

- This package contains the binary kernel image and pre-built binary modules for a particular arch/featureset/flavour combination. Names of the files installed by this package are architecture-dependent. Typical locations of essential files for the `i386` architecture are:

  `/boot/vmlinuz-`version`-`abiname`[-`featureset`]-`flavour``

- The binary (compressed) kernel image.

`/boot/initrd.img-`version`-`abiname`[-`featureset`]-`flavour``

- Initial RAM filesystem (initramfs) image. Note, that this file is automatically generated in the installation process and is not shipped as a part of the package. See ch-initramfs for more details.

`/boot/config-`version`-`abiname`[-`featureset`]-`flavour``

- The kernel configuration file used to build this particular kernel. May be used to rebuild the kernel from source, if necessary.

`/lib/modules/`version`-`abiname`[-`featureset`]-`flavour`/`

- Directory containing the pre-built binary kernel modules.

`linux-image-`version`-`abiname`[-`featureset`]-`flavour`-unsigned`

- This package contains the binary kernel image and pre-built binary modules for a particular arch/featureset/flavour combination, that are meant to be signed and copied into a package without the `-unsigned` suffix. There is normally no need to install these packages.

`linux-libc-dev`

- This package provides Linux kernel headers for use by userspace programs, such as GNU glibc and other system libraries.