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