| 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/driver-api/early-userspace/early_userspace_support.rst> 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 | default y |
| 58 | select DECOMPRESS_GZIP |
| 59 | help |
| 60 | Support loading of a gzip encoded initial ramdisk or cpio buffer. |
| 61 | If unsure, say Y. |
| 62 | |
| 63 | config RD_BZIP2 |
| 64 | bool "Support initial ramdisk/ramfs compressed using bzip2" |
| 65 | default y |
| 66 | select DECOMPRESS_BZIP2 |
| 67 | help |
| 68 | Support loading of a bzip2 encoded initial ramdisk or cpio buffer |
| 69 | If unsure, say N. |
| 70 | |
| 71 | config RD_LZMA |
| 72 | bool "Support initial ramdisk/ramfs compressed using LZMA" |
| 73 | default y |
| 74 | select DECOMPRESS_LZMA |
| 75 | help |
| 76 | Support loading of a LZMA encoded initial ramdisk or cpio buffer |
| 77 | If unsure, say N. |
| 78 | |
| 79 | config RD_XZ |
| 80 | bool "Support initial ramdisk/ramfs compressed using XZ" |
| 81 | default y |
| 82 | select DECOMPRESS_XZ |
| 83 | help |
| 84 | Support loading of a XZ encoded initial ramdisk or cpio buffer. |
| 85 | If unsure, say N. |
| 86 | |
| 87 | config RD_LZO |
| 88 | bool "Support initial ramdisk/ramfs compressed using LZO" |
| 89 | default y |
| 90 | select DECOMPRESS_LZO |
| 91 | help |
| 92 | Support loading of a LZO encoded initial ramdisk or cpio buffer |
| 93 | If unsure, say N. |
| 94 | |
| 95 | config RD_LZ4 |
| 96 | bool "Support initial ramdisk/ramfs compressed using LZ4" |
| 97 | default y |
| 98 | select DECOMPRESS_LZ4 |
| 99 | help |
| 100 | Support loading of a LZ4 encoded initial ramdisk or cpio buffer |
| 101 | If unsure, say N. |
| 102 | |
| 103 | config RD_ZSTD |
| 104 | bool "Support initial ramdisk/ramfs compressed using ZSTD" |
| 105 | default y |
| 106 | select DECOMPRESS_ZSTD |
| 107 | help |
| 108 | Support loading of a ZSTD encoded initial ramdisk or cpio buffer. |
| 109 | If unsure, say N. |
| 110 | |
| 111 | choice |
| 112 | prompt "Built-in initramfs compression mode" |
| 113 | depends on INITRAMFS_SOURCE != "" |
| 114 | help |
| 115 | This option allows you to decide by which algorithm the builtin |
| 116 | initramfs will be compressed. Several compression algorithms are |
| 117 | available, which differ in efficiency, compression and |
| 118 | decompression speed. Compression speed is only relevant |
| 119 | when building a kernel. Decompression speed is relevant at |
| 120 | each boot. Also the memory usage during decompression may become |
| 121 | relevant on memory constrained systems. This is usually based on the |
| 122 | dictionary size of the algorithm with algorithms like XZ and LZMA |
| 123 | featuring large dictionary sizes. |
| 124 | |
| 125 | High compression options are mostly useful for users who are |
| 126 | low on RAM, since it reduces the memory consumption during |
| 127 | boot. |
| 128 | |
| 129 | Keep in mind that your build system needs to provide the appropriate |
| 130 | compression tool to compress the generated initram cpio file for |
| 131 | embedding. |
| 132 | |
| 133 | If in doubt, select 'None' |
| 134 | |
| 135 | config INITRAMFS_COMPRESSION_GZIP |
| 136 | bool "Gzip" |
| 137 | depends on RD_GZIP |
| 138 | help |
| 139 | Use the old and well tested gzip compression algorithm. Gzip provides |
| 140 | a good balance between compression ratio and decompression speed and |
| 141 | has a reasonable compression speed. It is also more likely to be |
| 142 | supported by your build system as the gzip tool is present by default |
| 143 | on most distros. |
| 144 | |
| 145 | config INITRAMFS_COMPRESSION_BZIP2 |
| 146 | bool "Bzip2" |
| 147 | depends on RD_BZIP2 |
| 148 | help |
| 149 | It's compression ratio and speed is intermediate. Decompression speed |
| 150 | is slowest among the choices. The initramfs size is about 10% smaller |
| 151 | with bzip2, in comparison to gzip. Bzip2 uses a large amount of |
| 152 | memory. For modern kernels you will need at least 8MB RAM or more for |
| 153 | booting. |
| 154 | |
| 155 | If you choose this, keep in mind that you need to have the bzip2 tool |
| 156 | available to be able to compress the initram. |
| 157 | |
| 158 | config INITRAMFS_COMPRESSION_LZMA |
| 159 | bool "LZMA" |
| 160 | depends on RD_LZMA |
| 161 | help |
| 162 | This algorithm's compression ratio is best but has a large dictionary |
| 163 | size which might cause issues in memory constrained systems. |
| 164 | Decompression speed is between the other choices. Compression is |
| 165 | slowest. The initramfs size is about 33% smaller with LZMA in |
| 166 | comparison to gzip. |
| 167 | |
| 168 | If you choose this, keep in mind that you may need to install the xz |
| 169 | or lzma tools to be able to compress the initram. |
| 170 | |
| 171 | config INITRAMFS_COMPRESSION_XZ |
| 172 | bool "XZ" |
| 173 | depends on RD_XZ |
| 174 | help |
| 175 | XZ uses the LZMA2 algorithm and has a large dictionary which may cause |
| 176 | problems on memory constrained systems. The initramfs size is about |
| 177 | 30% smaller with XZ in comparison to gzip. Decompression speed is |
| 178 | better than that of bzip2 but worse than gzip and LZO. Compression is |
| 179 | slow. |
| 180 | |
| 181 | If you choose this, keep in mind that you may need to install the xz |
| 182 | tool to be able to compress the initram. |
| 183 | |
| 184 | config INITRAMFS_COMPRESSION_LZO |
| 185 | bool "LZO" |
| 186 | depends on RD_LZO |
| 187 | help |
| 188 | It's compression ratio is the second poorest amongst the choices. The |
| 189 | kernel size is about 10% bigger than gzip. Despite that, it's |
| 190 | decompression speed is the second fastest and it's compression speed |
| 191 | is quite fast too. |
| 192 | |
| 193 | If you choose this, keep in mind that you may need to install the lzop |
| 194 | tool to be able to compress the initram. |
| 195 | |
| 196 | config INITRAMFS_COMPRESSION_LZ4 |
| 197 | bool "LZ4" |
| 198 | depends on RD_LZ4 |
| 199 | help |
| 200 | It's compression ratio is the poorest amongst the choices. The kernel |
| 201 | size is about 15% bigger than gzip; however its decompression speed |
| 202 | is the fastest. |
| 203 | |
| 204 | If you choose this, keep in mind that most distros don't provide lz4 |
| 205 | by default which could cause a build failure. |
| 206 | |
| 207 | config INITRAMFS_COMPRESSION_ZSTD |
| 208 | bool "ZSTD" |
| 209 | depends on RD_ZSTD |
| 210 | help |
| 211 | ZSTD is a compression algorithm targeting intermediate compression |
| 212 | with fast decompression speed. It will compress better than GZIP and |
| 213 | decompress around the same speed as LZO, but slower than LZ4. |
| 214 | |
| 215 | If you choose this, keep in mind that you may need to install the zstd |
| 216 | tool to be able to compress the initram. |
| 217 | |
| 218 | config INITRAMFS_COMPRESSION_NONE |
| 219 | bool "None" |
| 220 | help |
| 221 | Do not compress the built-in initramfs at all. This may sound wasteful |
| 222 | in space, but, you should be aware that the built-in initramfs will be |
| 223 | compressed at a later stage anyways along with the rest of the kernel, |
| 224 | on those architectures that support this. However, not compressing the |
| 225 | initramfs may lead to slightly higher memory consumption during a |
| 226 | short time at boot, while both the cpio image and the unpacked |
| 227 | filesystem image will be present in memory simultaneously |
| 228 | |
| 229 | endchoice |