linux/usr/Kconfig
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   1#
   2# Configuration for initramfs
   3#
   4
   5config 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
  24config INITRAMFS_ROOT_UID
  25        int "User ID to map to 0 (user root)"
  26        depends on INITRAMFS_SOURCE!=""
  27        default "0"
  28        help
  29          This setting is only meaningful if the INITRAMFS_SOURCE is
  30          contains a directory.  Setting this user ID (UID) to something
  31          other than "0" will cause all files owned by that UID to be
  32          owned by user root in the initial ramdisk image.
  33
  34          If you are not sure, leave it set to "0".
  35
  36config INITRAMFS_ROOT_GID
  37        int "Group ID to map to 0 (group root)"
  38        depends on INITRAMFS_SOURCE!=""
  39        default "0"
  40        help
  41          This setting is only meaningful if the INITRAMFS_SOURCE is
  42          contains a directory.  Setting this group ID (GID) to something
  43          other than "0" will cause all files owned by that GID to be
  44          owned by group root in the initial ramdisk image.
  45
  46          If you are not sure, leave it set to "0".
  47
  48config RD_GZIP
  49        bool "Support initial ramdisks compressed using gzip" if EXPERT
  50        default y
  51        depends on BLK_DEV_INITRD
  52        select DECOMPRESS_GZIP
  53        help
  54          Support loading of a gzip encoded initial ramdisk or cpio buffer.
  55          If unsure, say Y.
  56
  57config RD_BZIP2
  58        bool "Support initial ramdisks compressed using bzip2" if EXPERT
  59        default !EXPERT
  60        depends on BLK_DEV_INITRD
  61        select DECOMPRESS_BZIP2
  62        help
  63          Support loading of a bzip2 encoded initial ramdisk or cpio buffer
  64          If unsure, say N.
  65
  66config RD_LZMA
  67        bool "Support initial ramdisks compressed using LZMA" if EXPERT
  68        default !EXPERT
  69        depends on BLK_DEV_INITRD
  70        select DECOMPRESS_LZMA
  71        help
  72          Support loading of a LZMA encoded initial ramdisk or cpio buffer
  73          If unsure, say N.
  74
  75config RD_XZ
  76        bool "Support initial ramdisks compressed using XZ" if EXPERT
  77        default !EXPERT
  78        depends on BLK_DEV_INITRD
  79        select DECOMPRESS_XZ
  80        help
  81          Support loading of a XZ encoded initial ramdisk or cpio buffer.
  82          If unsure, say N.
  83
  84config RD_LZO
  85        bool "Support initial ramdisks compressed using LZO" if EXPERT
  86        default !EXPERT
  87        depends on BLK_DEV_INITRD
  88        select DECOMPRESS_LZO
  89        help
  90          Support loading of a LZO encoded initial ramdisk or cpio buffer
  91          If unsure, say N.
  92
  93config RD_LZ4
  94        bool "Support initial ramdisks compressed using LZ4" if EXPERT
  95        default !EXPERT
  96        depends on BLK_DEV_INITRD
  97        select DECOMPRESS_LZ4
  98        help
  99          Support loading of a LZ4 encoded initial ramdisk or cpio buffer
 100          If unsure, say N.
 101
 102choice
 103        prompt "Built-in initramfs compression mode" if INITRAMFS_SOURCE!=""
 104        help
 105          This option decides by which algorithm the builtin initramfs
 106          will be compressed.  Several compression algorithms are
 107          available, which differ in efficiency, compression and
 108          decompression speed.  Compression speed is only relevant
 109          when building a kernel.  Decompression speed is relevant at
 110          each boot.
 111
 112          If you have any problems with bzip2 or LZMA compressed
 113          initramfs, mail me (Alain Knaff) <alain@knaff.lu>.
 114
 115          High compression options are mostly useful for users who are
 116          low on RAM, since it reduces the memory consumption during
 117          boot.
 118
 119          If in doubt, select 'gzip'
 120
 121config INITRAMFS_COMPRESSION_NONE
 122        bool "None"
 123        help
 124          Do not compress the built-in initramfs at all. This may
 125          sound wasteful in space, but, you should be aware that the
 126          built-in initramfs will be compressed at a later stage
 127          anyways along with the rest of the kernel, on those
 128          architectures that support this.
 129          However, not compressing the initramfs may lead to slightly
 130          higher memory consumption during a short time at boot, while
 131          both the cpio image and the unpacked filesystem image will
 132          be present in memory simultaneously
 133
 134config INITRAMFS_COMPRESSION_GZIP
 135        bool "Gzip"
 136        depends on RD_GZIP
 137        help
 138          The old and tried gzip compression. It provides a good balance
 139          between compression ratio and decompression speed.
 140
 141config INITRAMFS_COMPRESSION_BZIP2
 142        bool "Bzip2"
 143        depends on RD_BZIP2
 144        help
 145          Its compression ratio and speed is intermediate.
 146          Decompression speed is slowest among the choices.  The initramfs
 147          size is about 10% smaller with bzip2, in comparison to gzip.
 148          Bzip2 uses a large amount of memory. For modern kernels you
 149          will need at least 8MB RAM or more for booting.
 150
 151config INITRAMFS_COMPRESSION_LZMA
 152        bool "LZMA"
 153        depends on RD_LZMA
 154        help
 155          This algorithm's compression ratio is best.
 156          Decompression speed is between the other choices.
 157          Compression is slowest. The initramfs size is about 33%
 158          smaller with LZMA in comparison to gzip.
 159
 160config INITRAMFS_COMPRESSION_XZ
 161        bool "XZ"
 162        depends on RD_XZ
 163        help
 164          XZ uses the LZMA2 algorithm. The initramfs size is about 30%
 165          smaller with XZ in comparison to gzip. Decompression speed
 166          is better than that of bzip2 but worse than gzip and LZO.
 167          Compression is slow.
 168
 169config INITRAMFS_COMPRESSION_LZO
 170        bool "LZO"
 171        depends on RD_LZO
 172        help
 173          Its compression ratio is the poorest among the choices. The kernel
 174          size is about 10% bigger than gzip; however its speed
 175          (both compression and decompression) is the fastest.
 176
 177endchoice
 178
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