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785d74ec3b
Even though INITRAMFS_SOURCE kconfig option isn't set in most of
defconfigs it is used (set) extensively by various build systems.
Commit f26661e127 ("initramfs: make initramfs compression choice
non-optional") has changed default compression mode. Previously we
compress initramfs using available compression algorithm. Now
we don't use any compression at all by default.
It significantly increases the image size in case of build system
chooses embedded initramfs. Initially I faced with this issue while
using buildroot.
As of today it's not possible to set preferred compression mode
in target defconfig as this option depends on INITRAMFS_SOURCE
being set. Modification of all build systems either doesn't look
like good option.
Let's instead rewrite initramfs compression mode choices list
the way that "INITRAMFS_COMPRESSION_NONE" will be the last option
in the list. In that case it will be chosen only if all other
options (which implements any compression) are not available.
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
210 lines
7.1 KiB
Text
210 lines
7.1 KiB
Text
# 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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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_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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