1# SPDX-License-Identifier: GPL-2.0 2# 3# Configuration for initramfs 4# 5 6config 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 25config 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 35config 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 45config 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 55config 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 63config 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 71config 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 79config 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 87config 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 95config 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 103choice 104 prompt "Built-in initramfs compression mode" 105 depends on INITRAMFS_SOURCE!="" 106 optional 107 help 108 This option allows you to decide by which algorithm the builtin 109 initramfs will be compressed. Several compression algorithms are 110 available, which differ in efficiency, compression and 111 decompression speed. Compression speed is only relevant 112 when building a kernel. Decompression speed is relevant at 113 each boot. Also the memory usage during decompression may become 114 relevant on memory constrained systems. This is usually based on the 115 dictionary size of the algorithm with algorithms like XZ and LZMA 116 featuring large dictionary sizes. 117 118 High compression options are mostly useful for users who are 119 low on RAM, since it reduces the memory consumption during 120 boot. 121 122 Keep in mind that your build system needs to provide the appropriate 123 compression tool to compress the generated initram cpio file for 124 embedding. 125 126 If in doubt, select 'None' 127 128config INITRAMFS_COMPRESSION_NONE 129 bool "None" 130 help 131 Do not compress the built-in initramfs at all. This may sound wasteful 132 in space, but, you should be aware that the built-in initramfs will be 133 compressed at a later stage anyways along with the rest of the kernel, 134 on those architectures that support this. However, not compressing the 135 initramfs may lead to slightly higher memory consumption during a 136 short time at boot, while both the cpio image and the unpacked 137 filesystem image will be present in memory simultaneously 138 139config INITRAMFS_COMPRESSION_GZIP 140 bool "Gzip" 141 depends on RD_GZIP 142 help 143 Use the old and well tested gzip compression algorithm. Gzip provides 144 a good balance between compression ratio and decompression speed and 145 has a reasonable compression speed. It is also more likely to be 146 supported by your build system as the gzip tool is present by default 147 on most distros. 148 149config INITRAMFS_COMPRESSION_BZIP2 150 bool "Bzip2" 151 depends on RD_BZIP2 152 help 153 It's compression ratio and speed is intermediate. Decompression speed 154 is slowest among the choices. The initramfs size is about 10% smaller 155 with bzip2, in comparison to gzip. Bzip2 uses a large amount of 156 memory. For modern kernels you will need at least 8MB RAM or more for 157 booting. 158 159 If you choose this, keep in mind that you need to have the bzip2 tool 160 available to be able to compress the initram. 161 162config INITRAMFS_COMPRESSION_LZMA 163 bool "LZMA" 164 depends on RD_LZMA 165 help 166 This algorithm's compression ratio is best but has a large dictionary 167 size which might cause issues in memory constrained systems. 168 Decompression speed is between the other choices. Compression is 169 slowest. The initramfs size is about 33% smaller with LZMA in 170 comparison to gzip. 171 172 If you choose this, keep in mind that you may need to install the xz 173 or lzma tools to be able to compress the initram. 174 175config INITRAMFS_COMPRESSION_XZ 176 bool "XZ" 177 depends on RD_XZ 178 help 179 XZ uses the LZMA2 algorithm and has a large dictionary which may cause 180 problems on memory constrained systems. The initramfs size is about 181 30% smaller with XZ in comparison to gzip. Decompression speed is 182 better than that of bzip2 but worse than gzip and LZO. Compression is 183 slow. 184 185 If you choose this, keep in mind that you may need to install the xz 186 tool to be able to compress the initram. 187 188config INITRAMFS_COMPRESSION_LZO 189 bool "LZO" 190 depends on RD_LZO 191 help 192 It's compression ratio is the second poorest amongst the choices. The 193 kernel size is about 10% bigger than gzip. Despite that, it's 194 decompression speed is the second fastest and it's compression speed 195 is quite fast too. 196 197 If you choose this, keep in mind that you may need to install the lzop 198 tool to be able to compress the initram. 199 200config INITRAMFS_COMPRESSION_LZ4 201 bool "LZ4" 202 depends on RD_LZ4 203 help 204 It's compression ratio is the poorest amongst the choices. The kernel 205 size is about 15% bigger than gzip; however its decompression speed 206 is the fastest. 207 208 If you choose this, keep in mind that most distros don't provide lz4 209 by default which could cause a build failure. 210 211endchoice 212 213config INITRAMFS_COMPRESSION 214 depends on INITRAMFS_SOURCE!="" 215 string 216 default "" if INITRAMFS_COMPRESSION_NONE 217 default ".gz" if INITRAMFS_COMPRESSION_GZIP 218 default ".bz2" if INITRAMFS_COMPRESSION_BZIP2 219 default ".lzma" if INITRAMFS_COMPRESSION_LZMA 220 default ".xz" if INITRAMFS_COMPRESSION_XZ 221 default ".lzo" if INITRAMFS_COMPRESSION_LZO 222 default ".lz4" if INITRAMFS_COMPRESSION_LZ4 223 default ".gz" if RD_GZIP 224 default ".lz4" if RD_LZ4 225 default ".lzo" if RD_LZO 226 default ".xz" if RD_XZ 227 default ".lzma" if RD_LZMA 228 default ".bz2" if RD_BZIP2 229 default "" 230