usr/Kconfig

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