usr/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0
   2 #
   3 # Configuration for initramfs
   4 #
   5
   6 config INITRAMFS_SOURCE
   7         string "Initramfs source file(s)"
   8         default ""
   9         help
  10           This can be either a single cpio archive with a .cpio suffix or a
  11           space-separated list of directories and files for building the
  12           initramfs image.  A cpio archive should contain a filesystem archive
  13           to be used as an initramfs image.  Directories should contain a
  14           filesystem layout to be included in the initramfs image.  Files
  15           should contain entries according to the format described by the
  16           "usr/gen_init_cpio" program in the kernel tree.
  17
  18           When multiple directories and files are specified then the
  19           initramfs image will be the aggregate of all of them.
  20
  21           See <file:Documentation/early-userspace/README> for more details.
  22
  23           If you are not sure, leave it blank.
  24
  25 config INITRAMFS_FORCE
  26         bool "Ignore the initramfs passed by the bootloader"
  27         depends on CMDLINE_EXTEND || CMDLINE_FORCE
  28         help
  29           This option causes the kernel to ignore the initramfs image
  30           (or initrd image) passed to it by the bootloader. This is
  31           analogous to CMDLINE_FORCE, which is found on some architectures,
  32           and is useful if you cannot or don't want to change the image
  33           your bootloader passes to the kernel.
  34
  35 config INITRAMFS_ROOT_UID
  36         int "User ID to map to 0 (user root)"
  37         depends on INITRAMFS_SOURCE!=""
  38         default "0"
  39         help
  40           If INITRAMFS_SOURCE points to a directory, files owned by this UID
  41           (-1 = current user) will be owned by root in the resulting image.
  42
  43           If you are not sure, leave it set to "0".
  44
  45 config INITRAMFS_ROOT_GID
  46         int "Group ID to map to 0 (group root)"
  47         depends on INITRAMFS_SOURCE!=""
  48         default "0"
  49         help
  50           If INITRAMFS_SOURCE points to a directory, files owned by this GID
  51           (-1 = current group) will be owned by root in the resulting image.
  52
  53           If you are not sure, leave it set to "0".
  54
  55 config RD_GZIP
  56         bool "Support initial ramdisk/ramfs compressed using gzip"
  57         depends on BLK_DEV_INITRD
  58         default y
  59         select DECOMPRESS_GZIP
  60         help
  61           Support loading of a gzip encoded initial ramdisk or cpio buffer.
  62           If unsure, say Y.
  63
  64 config RD_BZIP2
  65         bool "Support initial ramdisk/ramfs compressed using bzip2"
  66         default y
  67         depends on BLK_DEV_INITRD
  68         select DECOMPRESS_BZIP2
  69         help
  70           Support loading of a bzip2 encoded initial ramdisk or cpio buffer
  71           If unsure, say N.
  72
  73 config RD_LZMA
  74         bool "Support initial ramdisk/ramfs compressed using LZMA"
  75         default y
  76         depends on BLK_DEV_INITRD
  77         select DECOMPRESS_LZMA
  78         help
  79           Support loading of a LZMA encoded initial ramdisk or cpio buffer
  80           If unsure, say N.
  81
  82 config RD_XZ
  83         bool "Support initial ramdisk/ramfs compressed using XZ"
  84         depends on BLK_DEV_INITRD
  85         default y
  86         select DECOMPRESS_XZ
  87         help
  88           Support loading of a XZ encoded initial ramdisk or cpio buffer.
  89           If unsure, say N.
  90
  91 config RD_LZO
  92         bool "Support initial ramdisk/ramfs compressed using LZO"
  93         default y
  94         depends on BLK_DEV_INITRD
  95         select DECOMPRESS_LZO
  96         help
  97           Support loading of a LZO encoded initial ramdisk or cpio buffer
  98           If unsure, say N.
  99
 100 config RD_LZ4
 101         bool "Support initial ramdisk/ramfs compressed using LZ4"
 102         default y
 103         depends on BLK_DEV_INITRD
 104         select DECOMPRESS_LZ4
 105         help
 106           Support loading of a LZ4 encoded initial ramdisk or cpio buffer
 107           If unsure, say N.
 108
 109 choice
 110         prompt "Built-in initramfs compression mode"
 111         depends on INITRAMFS_SOURCE!=""
 112         optional
 113         help
 114           This option allows you to decide by which algorithm the builtin
 115           initramfs will be compressed.  Several compression algorithms are
 116           available, which differ in efficiency, compression and
 117           decompression speed.  Compression speed is only relevant
 118           when building a kernel.  Decompression speed is relevant at
 119           each boot. Also the memory usage during decompression may become
 120           relevant on memory constrained systems. This is usually based on the
 121           dictionary size of the algorithm with algorithms like XZ and LZMA
 122           featuring large dictionary sizes.
 123
 124           High compression options are mostly useful for users who are
 125           low on RAM, since it reduces the memory consumption during
 126           boot.
 127
 128           Keep in mind that your build system needs to provide the appropriate
 129           compression tool to compress the generated initram cpio file for
 130           embedding.
 131
 132           If in doubt, select 'None'
 133
 134 config INITRAMFS_COMPRESSION_NONE
 135         bool "None"
 136         help
 137           Do not compress the built-in initramfs at all. This may sound wasteful
 138           in space, but, you should be aware that the built-in initramfs will be
 139           compressed at a later stage anyways along with the rest of the kernel,
 140           on those architectures that support this. However, not compressing the
 141           initramfs may lead to slightly higher memory consumption during a
 142           short time at boot, while both the cpio image and the unpacked
 143           filesystem image will be present in memory simultaneously
 144
 145 config INITRAMFS_COMPRESSION_GZIP
 146         bool "Gzip"
 147         depends on RD_GZIP
 148         help
 149           Use the old and well tested gzip compression algorithm. Gzip provides
 150           a good balance between compression ratio and decompression speed and
 151           has a reasonable compression speed. It is also more likely to be
 152           supported by your build system as the gzip tool is present by default
 153           on most distros.
 154
 155 config INITRAMFS_COMPRESSION_BZIP2
 156         bool "Bzip2"
 157         depends on RD_BZIP2
 158         help
 159           It's compression ratio and speed is intermediate. Decompression speed
 160           is slowest among the choices. The initramfs size is about 10% smaller
 161           with bzip2, in comparison to gzip. Bzip2 uses a large amount of
 162           memory. For modern kernels you will need at least 8MB RAM or more for
 163           booting.
 164
 165           If you choose this, keep in mind that you need to have the bzip2 tool
 166           available to be able to compress the initram.
 167
 168 config INITRAMFS_COMPRESSION_LZMA
 169         bool "LZMA"
 170         depends on RD_LZMA
 171         help
 172           This algorithm's compression ratio is best but has a large dictionary
 173           size which might cause issues in memory constrained systems.
 174           Decompression speed is between the other choices. Compression is
 175           slowest. The initramfs size is about 33% smaller with LZMA in
 176           comparison to gzip.
 177
 178           If you choose this, keep in mind that you may need to install the xz
 179           or lzma tools to be able to compress the initram.
 180
 181 config INITRAMFS_COMPRESSION_XZ
 182         bool "XZ"
 183         depends on RD_XZ
 184         help
 185           XZ uses the LZMA2 algorithm and has a large dictionary which may cause
 186           problems on memory constrained systems. The initramfs size is about
 187           30% smaller with XZ in comparison to gzip. Decompression speed is
 188           better than that of bzip2 but worse than gzip and LZO. Compression is
 189           slow.
 190
 191           If you choose this, keep in mind that you may need to install the xz
 192           tool to be able to compress the initram.
 193
 194 config INITRAMFS_COMPRESSION_LZO
 195         bool "LZO"
 196         depends on RD_LZO
 197         help
 198           It's compression ratio is the second poorest amongst the choices. The
 199           kernel size is about 10% bigger than gzip. Despite that, it's
 200           decompression speed is the second fastest and it's compression speed
 201           is quite fast too.
 202
 203           If you choose this, keep in mind that you may need to install the lzop
 204           tool to be able to compress the initram.
 205
 206 config INITRAMFS_COMPRESSION_LZ4
 207         bool "LZ4"
 208         depends on RD_LZ4
 209         help
 210           It's compression ratio is the poorest amongst the choices. The kernel
 211           size is about 15% bigger than gzip; however its decompression speed
 212           is the fastest.
 213
 214           If you choose this, keep in mind that most distros don't provide lz4
 215           by default which could cause a build failure.
 216
 217 endchoice
 218
 219 config INITRAMFS_COMPRESSION
 220         depends on INITRAMFS_SOURCE!=""
 221         string
 222         default ""      if INITRAMFS_COMPRESSION_NONE
 223         default ".gz"   if INITRAMFS_COMPRESSION_GZIP
 224         default ".bz2"  if INITRAMFS_COMPRESSION_BZIP2
 225         default ".lzma" if INITRAMFS_COMPRESSION_LZMA
 226         default ".xz"   if INITRAMFS_COMPRESSION_XZ
 227         default ".lzo"  if INITRAMFS_COMPRESSION_LZO
 228         default ".lz4"  if INITRAMFS_COMPRESSION_LZ4
 229         default ".gz"   if RD_GZIP
 230         default ".lz4"  if RD_LZ4
 231         default ".lzo"  if RD_LZO
 232         default ".xz"   if RD_XZ
 233         default ".lzma" if RD_LZMA
 234         default ".bz2"  if RD_BZIP2
 235         default ""