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