| # SPDX-License-Identifier: GPL-2.0 |
| # |
| # Configuration for initramfs |
| # |
| |
| config INITRAMFS_SOURCE |
| string "Initramfs source file(s)" |
| default "" |
| help |
| This can be either a single cpio archive with a .cpio suffix or a |
| space-separated list of directories and files for building the |
| initramfs image. A cpio archive should contain a filesystem archive |
| to be used as an initramfs image. Directories should contain a |
| filesystem layout to be included in the initramfs image. Files |
| should contain entries according to the format described by the |
| "usr/gen_init_cpio" program in the kernel tree. |
| |
| When multiple directories and files are specified then the |
| initramfs image will be the aggregate of all of them. |
| |
| See <file:Documentation/driver-api/early-userspace/early_userspace_support.rst> for more details. |
| |
| If you are not sure, leave it blank. |
| |
| config INITRAMFS_FORCE |
| bool "Ignore the initramfs passed by the bootloader" |
| depends on CMDLINE_EXTEND || CMDLINE_FORCE |
| help |
| This option causes the kernel to ignore the initramfs image |
| (or initrd image) passed to it by the bootloader. This is |
| analogous to CMDLINE_FORCE, which is found on some architectures, |
| and is useful if you cannot or don't want to change the image |
| your bootloader passes to the kernel. |
| |
| config INITRAMFS_ROOT_UID |
| int "User ID to map to 0 (user root)" |
| depends on INITRAMFS_SOURCE!="" |
| default "0" |
| help |
| If INITRAMFS_SOURCE points to a directory, files owned by this UID |
| (-1 = current user) will be owned by root in the resulting image. |
| |
| If you are not sure, leave it set to "0". |
| |
| config INITRAMFS_ROOT_GID |
| int "Group ID to map to 0 (group root)" |
| depends on INITRAMFS_SOURCE!="" |
| default "0" |
| help |
| If INITRAMFS_SOURCE points to a directory, files owned by this GID |
| (-1 = current group) will be owned by root in the resulting image. |
| |
| If you are not sure, leave it set to "0". |
| |
| config RD_GZIP |
| bool "Support initial ramdisk/ramfs compressed using gzip" |
| default y |
| select DECOMPRESS_GZIP |
| help |
| Support loading of a gzip encoded initial ramdisk or cpio buffer. |
| If unsure, say Y. |
| |
| config RD_BZIP2 |
| bool "Support initial ramdisk/ramfs compressed using bzip2" |
| default y |
| select DECOMPRESS_BZIP2 |
| help |
| Support loading of a bzip2 encoded initial ramdisk or cpio buffer |
| If unsure, say N. |
| |
| config RD_LZMA |
| bool "Support initial ramdisk/ramfs compressed using LZMA" |
| default y |
| select DECOMPRESS_LZMA |
| help |
| Support loading of a LZMA encoded initial ramdisk or cpio buffer |
| If unsure, say N. |
| |
| config RD_XZ |
| bool "Support initial ramdisk/ramfs compressed using XZ" |
| default y |
| select DECOMPRESS_XZ |
| help |
| Support loading of a XZ encoded initial ramdisk or cpio buffer. |
| If unsure, say N. |
| |
| config RD_LZO |
| bool "Support initial ramdisk/ramfs compressed using LZO" |
| default y |
| select DECOMPRESS_LZO |
| help |
| Support loading of a LZO encoded initial ramdisk or cpio buffer |
| If unsure, say N. |
| |
| config RD_LZ4 |
| bool "Support initial ramdisk/ramfs compressed using LZ4" |
| default y |
| select DECOMPRESS_LZ4 |
| help |
| Support loading of a LZ4 encoded initial ramdisk or cpio buffer |
| If unsure, say N. |
| |
| choice |
| prompt "Built-in initramfs compression mode" |
| depends on INITRAMFS_SOURCE != "" |
| help |
| This option allows you to decide by which algorithm the builtin |
| initramfs will be compressed. Several compression algorithms are |
| available, which differ in efficiency, compression and |
| decompression speed. Compression speed is only relevant |
| when building a kernel. Decompression speed is relevant at |
| each boot. Also the memory usage during decompression may become |
| relevant on memory constrained systems. This is usually based on the |
| dictionary size of the algorithm with algorithms like XZ and LZMA |
| featuring large dictionary sizes. |
| |
| High compression options are mostly useful for users who are |
| low on RAM, since it reduces the memory consumption during |
| boot. |
| |
| Keep in mind that your build system needs to provide the appropriate |
| compression tool to compress the generated initram cpio file for |
| embedding. |
| |
| If in doubt, select 'None' |
| |
| config INITRAMFS_COMPRESSION_GZIP |
| bool "Gzip" |
| depends on RD_GZIP |
| help |
| Use the old and well tested gzip compression algorithm. Gzip provides |
| a good balance between compression ratio and decompression speed and |
| has a reasonable compression speed. It is also more likely to be |
| supported by your build system as the gzip tool is present by default |
| on most distros. |
| |
| config INITRAMFS_COMPRESSION_BZIP2 |
| bool "Bzip2" |
| depends on RD_BZIP2 |
| help |
| It's compression ratio and speed is intermediate. Decompression speed |
| is slowest among the choices. The initramfs size is about 10% smaller |
| with bzip2, in comparison to gzip. Bzip2 uses a large amount of |
| memory. For modern kernels you will need at least 8MB RAM or more for |
| booting. |
| |
| If you choose this, keep in mind that you need to have the bzip2 tool |
| available to be able to compress the initram. |
| |
| config INITRAMFS_COMPRESSION_LZMA |
| bool "LZMA" |
| depends on RD_LZMA |
| help |
| This algorithm's compression ratio is best but has a large dictionary |
| size which might cause issues in memory constrained systems. |
| Decompression speed is between the other choices. Compression is |
| slowest. The initramfs size is about 33% smaller with LZMA in |
| comparison to gzip. |
| |
| If you choose this, keep in mind that you may need to install the xz |
| or lzma tools to be able to compress the initram. |
| |
| config INITRAMFS_COMPRESSION_XZ |
| bool "XZ" |
| depends on RD_XZ |
| help |
| XZ uses the LZMA2 algorithm and has a large dictionary which may cause |
| problems on memory constrained systems. The initramfs size is about |
| 30% smaller with XZ in comparison to gzip. Decompression speed is |
| better than that of bzip2 but worse than gzip and LZO. Compression is |
| slow. |
| |
| If you choose this, keep in mind that you may need to install the xz |
| tool to be able to compress the initram. |
| |
| config INITRAMFS_COMPRESSION_LZO |
| bool "LZO" |
| depends on RD_LZO |
| help |
| It's compression ratio is the second poorest amongst the choices. The |
| kernel size is about 10% bigger than gzip. Despite that, it's |
| decompression speed is the second fastest and it's compression speed |
| is quite fast too. |
| |
| If you choose this, keep in mind that you may need to install the lzop |
| tool to be able to compress the initram. |
| |
| config INITRAMFS_COMPRESSION_LZ4 |
| bool "LZ4" |
| depends on RD_LZ4 |
| help |
| It's compression ratio is the poorest amongst the choices. The kernel |
| size is about 15% bigger than gzip; however its decompression speed |
| is the fastest. |
| |
| If you choose this, keep in mind that most distros don't provide lz4 |
| by default which could cause a build failure. |
| |
| config INITRAMFS_COMPRESSION_NONE |
| bool "None" |
| help |
| Do not compress the built-in initramfs at all. This may sound wasteful |
| in space, but, you should be aware that the built-in initramfs will be |
| compressed at a later stage anyways along with the rest of the kernel, |
| on those architectures that support this. However, not compressing the |
| initramfs may lead to slightly higher memory consumption during a |
| short time at boot, while both the cpio image and the unpacked |
| filesystem image will be present in memory simultaneously |
| |
| endchoice |
