1 # SPDX-License-Identifier: GPL-2.0 1 # SPDX-License-Identifier: GPL-2.0 2 # 2 # 3 # Configuration for initramfs 3 # Configuration for initramfs 4 # 4 # 5 5 6 config INITRAMFS_SOURCE 6 config INITRAMFS_SOURCE 7 string "Initramfs source file(s)" 7 string "Initramfs source file(s)" 8 default "" 8 default "" 9 help 9 help 10 This can be either a single cpio arc 10 This can be either a single cpio archive with a .cpio suffix or a 11 space-separated list of directories 11 space-separated list of directories and files for building the 12 initramfs image. A cpio archive sho 12 initramfs image. A cpio archive should contain a filesystem archive 13 to be used as an initramfs image. D 13 to be used as an initramfs image. Directories should contain a 14 filesystem layout to be included in 14 filesystem layout to be included in the initramfs image. Files 15 should contain entries according to 15 should contain entries according to the format described by the 16 "usr/gen_init_cpio" program in the k 16 "usr/gen_init_cpio" program in the kernel tree. 17 17 18 When multiple directories and files 18 When multiple directories and files are specified then the 19 initramfs image will be the aggregat 19 initramfs image will be the aggregate of all of them. 20 20 21 See <file:Documentation/driver-api/e 21 See <file:Documentation/driver-api/early-userspace/early_userspace_support.rst> for more details. 22 22 23 If you are not sure, leave it blank. 23 If you are not sure, leave it blank. 24 24 25 config INITRAMFS_FORCE 25 config INITRAMFS_FORCE 26 bool "Ignore the initramfs passed by t 26 bool "Ignore the initramfs passed by the bootloader" 27 depends on CMDLINE_EXTEND || CMDLINE_F 27 depends on CMDLINE_EXTEND || CMDLINE_FORCE 28 help 28 help 29 This option causes the kernel to ign 29 This option causes the kernel to ignore the initramfs image 30 (or initrd image) passed to it by th 30 (or initrd image) passed to it by the bootloader. This is 31 analogous to CMDLINE_FORCE, which is 31 analogous to CMDLINE_FORCE, which is found on some architectures, 32 and is useful if you cannot or don't 32 and is useful if you cannot or don't want to change the image 33 your bootloader passes to the kernel 33 your bootloader passes to the kernel. 34 34 35 config INITRAMFS_ROOT_UID 35 config INITRAMFS_ROOT_UID 36 int "User ID to map to 0 (user root)" 36 int "User ID to map to 0 (user root)" 37 depends on INITRAMFS_SOURCE!="" 37 depends on INITRAMFS_SOURCE!="" 38 default "0" 38 default "0" 39 help 39 help 40 If INITRAMFS_SOURCE points to a dire 40 If INITRAMFS_SOURCE points to a directory, files owned by this UID 41 (-1 = current user) will be owned by 41 (-1 = current user) will be owned by root in the resulting image. 42 42 43 If you are not sure, leave it set to 43 If you are not sure, leave it set to "0". 44 44 45 config INITRAMFS_ROOT_GID 45 config INITRAMFS_ROOT_GID 46 int "Group ID to map to 0 (group root) 46 int "Group ID to map to 0 (group root)" 47 depends on INITRAMFS_SOURCE!="" 47 depends on INITRAMFS_SOURCE!="" 48 default "0" 48 default "0" 49 help 49 help 50 If INITRAMFS_SOURCE points to a dire 50 If INITRAMFS_SOURCE points to a directory, files owned by this GID 51 (-1 = current group) will be owned b 51 (-1 = current group) will be owned by root in the resulting image. 52 52 53 If you are not sure, leave it set to 53 If you are not sure, leave it set to "0". 54 54 55 config RD_GZIP 55 config RD_GZIP 56 bool "Support initial ramdisk/ramfs co 56 bool "Support initial ramdisk/ramfs compressed using gzip" 57 default y 57 default y 58 select DECOMPRESS_GZIP 58 select DECOMPRESS_GZIP 59 help 59 help 60 Support loading of a gzip encoded in 60 Support loading of a gzip encoded initial ramdisk or cpio buffer. 61 If unsure, say Y. 61 If unsure, say Y. 62 62 63 config RD_BZIP2 63 config RD_BZIP2 64 bool "Support initial ramdisk/ramfs co 64 bool "Support initial ramdisk/ramfs compressed using bzip2" 65 default y 65 default y 66 select DECOMPRESS_BZIP2 66 select DECOMPRESS_BZIP2 67 help 67 help 68 Support loading of a bzip2 encoded i 68 Support loading of a bzip2 encoded initial ramdisk or cpio buffer 69 If unsure, say N. 69 If unsure, say N. 70 70 71 config RD_LZMA 71 config RD_LZMA 72 bool "Support initial ramdisk/ramfs co 72 bool "Support initial ramdisk/ramfs compressed using LZMA" 73 default y 73 default y 74 select DECOMPRESS_LZMA 74 select DECOMPRESS_LZMA 75 help 75 help 76 Support loading of a LZMA encoded in 76 Support loading of a LZMA encoded initial ramdisk or cpio buffer 77 If unsure, say N. 77 If unsure, say N. 78 78 79 config RD_XZ 79 config RD_XZ 80 bool "Support initial ramdisk/ramfs co 80 bool "Support initial ramdisk/ramfs compressed using XZ" 81 default y 81 default y 82 select DECOMPRESS_XZ 82 select DECOMPRESS_XZ 83 help 83 help 84 Support loading of a XZ encoded init 84 Support loading of a XZ encoded initial ramdisk or cpio buffer. 85 If unsure, say N. 85 If unsure, say N. 86 86 87 config RD_LZO 87 config RD_LZO 88 bool "Support initial ramdisk/ramfs co 88 bool "Support initial ramdisk/ramfs compressed using LZO" 89 default y 89 default y 90 select DECOMPRESS_LZO 90 select DECOMPRESS_LZO 91 help 91 help 92 Support loading of a LZO encoded ini 92 Support loading of a LZO encoded initial ramdisk or cpio buffer 93 If unsure, say N. 93 If unsure, say N. 94 94 95 config RD_LZ4 95 config RD_LZ4 96 bool "Support initial ramdisk/ramfs co 96 bool "Support initial ramdisk/ramfs compressed using LZ4" 97 default y 97 default y 98 select DECOMPRESS_LZ4 98 select DECOMPRESS_LZ4 99 help 99 help 100 Support loading of a LZ4 encoded ini 100 Support loading of a LZ4 encoded initial ramdisk or cpio buffer 101 If unsure, say N. 101 If unsure, say N. 102 102 103 config RD_ZSTD 103 config RD_ZSTD 104 bool "Support initial ramdisk/ramfs co 104 bool "Support initial ramdisk/ramfs compressed using ZSTD" 105 default y 105 default y >> 106 depends on BLK_DEV_INITRD 106 select DECOMPRESS_ZSTD 107 select DECOMPRESS_ZSTD 107 help 108 help 108 Support loading of a ZSTD encoded in 109 Support loading of a ZSTD encoded initial ramdisk or cpio buffer. 109 If unsure, say N. 110 If unsure, say N. 110 111 111 choice 112 choice 112 prompt "Built-in initramfs compression 113 prompt "Built-in initramfs compression mode" 113 depends on INITRAMFS_SOURCE != "" 114 depends on INITRAMFS_SOURCE != "" 114 help 115 help 115 This option allows you to decide by 116 This option allows you to decide by which algorithm the builtin 116 initramfs will be compressed. Sever 117 initramfs will be compressed. Several compression algorithms are 117 available, which differ in efficienc 118 available, which differ in efficiency, compression and 118 decompression speed. Compression sp 119 decompression speed. Compression speed is only relevant 119 when building a kernel. Decompressi 120 when building a kernel. Decompression speed is relevant at 120 each boot. Also the memory usage dur 121 each boot. Also the memory usage during decompression may become 121 relevant on memory constrained syste 122 relevant on memory constrained systems. This is usually based on the 122 dictionary size of the algorithm wit 123 dictionary size of the algorithm with algorithms like XZ and LZMA 123 featuring large dictionary sizes. 124 featuring large dictionary sizes. 124 125 125 High compression options are mostly 126 High compression options are mostly useful for users who are 126 low on RAM, since it reduces the mem 127 low on RAM, since it reduces the memory consumption during 127 boot. 128 boot. 128 129 129 Keep in mind that your build system 130 Keep in mind that your build system needs to provide the appropriate 130 compression tool to compress the gen 131 compression tool to compress the generated initram cpio file for 131 embedding. 132 embedding. 132 133 133 If in doubt, select 'None' 134 If in doubt, select 'None' 134 135 135 config INITRAMFS_COMPRESSION_GZIP 136 config INITRAMFS_COMPRESSION_GZIP 136 bool "Gzip" 137 bool "Gzip" 137 depends on RD_GZIP 138 depends on RD_GZIP 138 help 139 help 139 Use the old and well tested gzip com 140 Use the old and well tested gzip compression algorithm. Gzip provides 140 a good balance between compression r 141 a good balance between compression ratio and decompression speed and 141 has a reasonable compression speed. 142 has a reasonable compression speed. It is also more likely to be 142 supported by your build system as th 143 supported by your build system as the gzip tool is present by default 143 on most distros. 144 on most distros. 144 145 145 config INITRAMFS_COMPRESSION_BZIP2 146 config INITRAMFS_COMPRESSION_BZIP2 146 bool "Bzip2" 147 bool "Bzip2" 147 depends on RD_BZIP2 148 depends on RD_BZIP2 148 help 149 help 149 It's compression ratio and speed is 150 It's compression ratio and speed is intermediate. Decompression speed 150 is slowest among the choices. The in 151 is slowest among the choices. The initramfs size is about 10% smaller 151 with bzip2, in comparison to gzip. B 152 with bzip2, in comparison to gzip. Bzip2 uses a large amount of 152 memory. For modern kernels you will 153 memory. For modern kernels you will need at least 8MB RAM or more for 153 booting. 154 booting. 154 155 155 If you choose this, keep in mind tha 156 If you choose this, keep in mind that you need to have the bzip2 tool 156 available to be able to compress the 157 available to be able to compress the initram. 157 158 158 config INITRAMFS_COMPRESSION_LZMA 159 config INITRAMFS_COMPRESSION_LZMA 159 bool "LZMA" 160 bool "LZMA" 160 depends on RD_LZMA 161 depends on RD_LZMA 161 help 162 help 162 This algorithm's compression ratio i 163 This algorithm's compression ratio is best but has a large dictionary 163 size which might cause issues in mem 164 size which might cause issues in memory constrained systems. 164 Decompression speed is between the o 165 Decompression speed is between the other choices. Compression is 165 slowest. The initramfs size is about 166 slowest. The initramfs size is about 33% smaller with LZMA in 166 comparison to gzip. 167 comparison to gzip. 167 168 168 If you choose this, keep in mind tha 169 If you choose this, keep in mind that you may need to install the xz 169 or lzma tools to be able to compress 170 or lzma tools to be able to compress the initram. 170 171 171 config INITRAMFS_COMPRESSION_XZ 172 config INITRAMFS_COMPRESSION_XZ 172 bool "XZ" 173 bool "XZ" 173 depends on RD_XZ 174 depends on RD_XZ 174 help 175 help 175 XZ uses the LZMA2 algorithm and has 176 XZ uses the LZMA2 algorithm and has a large dictionary which may cause 176 problems on memory constrained syste 177 problems on memory constrained systems. The initramfs size is about 177 30% smaller with XZ in comparison to 178 30% smaller with XZ in comparison to gzip. Decompression speed is 178 better than that of bzip2 but worse 179 better than that of bzip2 but worse than gzip and LZO. Compression is 179 slow. 180 slow. 180 181 181 If you choose this, keep in mind tha 182 If you choose this, keep in mind that you may need to install the xz 182 tool to be able to compress the init 183 tool to be able to compress the initram. 183 184 184 config INITRAMFS_COMPRESSION_LZO 185 config INITRAMFS_COMPRESSION_LZO 185 bool "LZO" 186 bool "LZO" 186 depends on RD_LZO 187 depends on RD_LZO 187 help 188 help 188 Its compression ratio is the second !! 189 It's compression ratio is the second poorest amongst the choices. The 189 kernel size is about 10% bigger than !! 190 kernel size is about 10% bigger than gzip. Despite that, it's 190 decompression speed is the second fa !! 191 decompression speed is the second fastest and it's compression speed 191 is quite fast too. 192 is quite fast too. 192 193 193 If you choose this, keep in mind tha 194 If you choose this, keep in mind that you may need to install the lzop 194 tool to be able to compress the init 195 tool to be able to compress the initram. 195 196 196 config INITRAMFS_COMPRESSION_LZ4 197 config INITRAMFS_COMPRESSION_LZ4 197 bool "LZ4" 198 bool "LZ4" 198 depends on RD_LZ4 199 depends on RD_LZ4 199 help 200 help 200 It's compression ratio is the poores 201 It's compression ratio is the poorest amongst the choices. The kernel 201 size is about 15% bigger than gzip; 202 size is about 15% bigger than gzip; however its decompression speed 202 is the fastest. 203 is the fastest. 203 204 204 If you choose this, keep in mind tha 205 If you choose this, keep in mind that most distros don't provide lz4 205 by default which could cause a build 206 by default which could cause a build failure. 206 207 207 config INITRAMFS_COMPRESSION_ZSTD 208 config INITRAMFS_COMPRESSION_ZSTD 208 bool "ZSTD" 209 bool "ZSTD" 209 depends on RD_ZSTD 210 depends on RD_ZSTD 210 help 211 help 211 ZSTD is a compression algorithm targ 212 ZSTD is a compression algorithm targeting intermediate compression 212 with fast decompression speed. It wi 213 with fast decompression speed. It will compress better than GZIP and 213 decompress around the same speed as 214 decompress around the same speed as LZO, but slower than LZ4. 214 215 215 If you choose this, keep in mind tha 216 If you choose this, keep in mind that you may need to install the zstd 216 tool to be able to compress the init 217 tool to be able to compress the initram. 217 218 218 config INITRAMFS_COMPRESSION_NONE 219 config INITRAMFS_COMPRESSION_NONE 219 bool "None" 220 bool "None" 220 help 221 help 221 Do not compress the built-in initram 222 Do not compress the built-in initramfs at all. This may sound wasteful 222 in space, but, you should be aware t 223 in space, but, you should be aware that the built-in initramfs will be 223 compressed at a later stage anyways 224 compressed at a later stage anyways along with the rest of the kernel, 224 on those architectures that support 225 on those architectures that support this. However, not compressing the 225 initramfs may lead to slightly highe 226 initramfs may lead to slightly higher memory consumption during a 226 short time at boot, while both the c 227 short time at boot, while both the cpio image and the unpacked 227 filesystem image will be present in 228 filesystem image will be present in memory simultaneously 228 229 229 endchoice 230 endchoice
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