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/early-userspace/README> 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 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 64config 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 73config 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 82config 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 91config 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 100config 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 109choice 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 134config 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 145config 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 155config 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 168config 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 181config 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 194config 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 206config 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 217endchoice 218 219config 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 "" 236
