1# 2# Configuration for initramfs 3# 4 5config INITRAMFS_SOURCE 6 string "Initramfs source file(s)" 7 default "" 8 help 9 This can be either a single cpio archive with a .cpio suffix or a 10 space-separated list of directories and files for building the 11 initramfs image. A cpio archive should contain a filesystem archive 12 to be used as an initramfs image. Directories should contain a 13 filesystem layout to be included in the initramfs image. Files 14 should contain entries according to the format described by the 15 "usr/gen_init_cpio" program in the kernel tree. 16 17 When multiple directories and files are specified then the 18 initramfs image will be the aggregate of all of them. 19 20 See <file:Documentation/early-userspace/README> for more details. 21 22 If you are not sure, leave it blank. 23 24config INITRAMFS_FORCE 25 bool "Ignore the initramfs passed by the bootloader" 26 depends on CMDLINE_EXTEND || CMDLINE_FORCE 27 help 28 This option causes the kernel to ignore the initramfs image 29 (or initrd image) passed to it by the bootloader. This is 30 analogous to CMDLINE_FORCE, which is found on some architectures, 31 and is useful if you cannot or don't want to change the image 32 your bootloader passes to the kernel. 33 34config INITRAMFS_ROOT_UID 35 int "User ID to map to 0 (user root)" 36 depends on INITRAMFS_SOURCE!="" 37 default "0" 38 help 39 If INITRAMFS_SOURCE points to a directory, files owned by this UID 40 (-1 = current user) will be owned by root in the resulting image. 41 42 If you are not sure, leave it set to "0". 43 44config INITRAMFS_ROOT_GID 45 int "Group ID to map to 0 (group root)" 46 depends on INITRAMFS_SOURCE!="" 47 default "0" 48 help 49 If INITRAMFS_SOURCE points to a directory, files owned by this GID 50 (-1 = current group) will be owned by root in the resulting image. 51 52 If you are not sure, leave it set to "0". 53 54config RD_GZIP 55 bool "Support initial ramdisks compressed using gzip" 56 depends on BLK_DEV_INITRD 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 ramdisks compressed using bzip2" 65 default y 66 depends on BLK_DEV_INITRD 67 select DECOMPRESS_BZIP2 68 help 69 Support loading of a bzip2 encoded initial ramdisk or cpio buffer 70 If unsure, say N. 71 72config RD_LZMA 73 bool "Support initial ramdisks compressed using LZMA" 74 default y 75 depends on BLK_DEV_INITRD 76 select DECOMPRESS_LZMA 77 help 78 Support loading of a LZMA encoded initial ramdisk or cpio buffer 79 If unsure, say N. 80 81config RD_XZ 82 bool "Support initial ramdisks compressed using XZ" 83 depends on BLK_DEV_INITRD 84 default y 85 select DECOMPRESS_XZ 86 help 87 Support loading of a XZ encoded initial ramdisk or cpio buffer. 88 If unsure, say N. 89 90config RD_LZO 91 bool "Support initial ramdisks compressed using LZO" 92 default y 93 depends on BLK_DEV_INITRD 94 select DECOMPRESS_LZO 95 help 96 Support loading of a LZO encoded initial ramdisk or cpio buffer 97 If unsure, say N. 98 99config RD_LZ4 100 bool "Support initial ramdisks compressed using LZ4" 101 default y 102 depends on BLK_DEV_INITRD 103 select DECOMPRESS_LZ4 104 help 105 Support loading of a LZ4 encoded initial ramdisk or cpio buffer 106 If unsure, say N. 107 108choice 109 prompt "Built-in initramfs compression mode" 110 depends on INITRAMFS_SOURCE!="" 111 optional 112 help 113 This option allows you to decide by which algorithm the builtin 114 initramfs will be compressed. Several compression algorithms are 115 available, which differ in efficiency, compression and 116 decompression speed. Compression speed is only relevant 117 when building a kernel. Decompression speed is relevant at 118 each boot. Also the memory usage during decompression may become 119 relevant on memory constrained systems. This is usually based on the 120 dictionary size of the algorithm with algorithms like XZ and LZMA 121 featuring large dictionary sizes. 122 123 High compression options are mostly useful for users who are 124 low on RAM, since it reduces the memory consumption during 125 boot. 126 127 Keep in mind that your build system needs to provide the appropriate 128 compression tool to compress the generated initram cpio file for 129 embedding. 130 131 If in doubt, select 'None' 132 133config INITRAMFS_COMPRESSION_NONE 134 bool "None" 135 help 136 Do not compress the built-in initramfs at all. This may sound wasteful 137 in space, but, you should be aware that the built-in initramfs will be 138 compressed at a later stage anyways along with the rest of the kernel, 139 on those architectures that support this. However, not compressing the 140 initramfs may lead to slightly higher memory consumption during a 141 short time at boot, while both the cpio image and the unpacked 142 filesystem image will be present in memory simultaneously 143 144config INITRAMFS_COMPRESSION_GZIP 145 bool "Gzip" 146 depends on RD_GZIP 147 help 148 Use the old and well tested gzip compression algorithm. Gzip provides 149 a good balance between compression ratio and decompression speed and 150 has a reasonable compression speed. It is also more likely to be 151 supported by your build system as the gzip tool is present by default 152 on most distros. 153 154config INITRAMFS_COMPRESSION_BZIP2 155 bool "Bzip2" 156 depends on RD_BZIP2 157 help 158 It's compression ratio and speed is intermediate. Decompression speed 159 is slowest among the choices. The initramfs size is about 10% smaller 160 with bzip2, in comparison to gzip. Bzip2 uses a large amount of 161 memory. For modern kernels you will need at least 8MB RAM or more for 162 booting. 163 164 If you choose this, keep in mind that you need to have the bzip2 tool 165 available to be able to compress the initram. 166 167config INITRAMFS_COMPRESSION_LZMA 168 bool "LZMA" 169 depends on RD_LZMA 170 help 171 This algorithm's compression ratio is best but has a large dictionary 172 size which might cause issues in memory constrained systems. 173 Decompression speed is between the other choices. Compression is 174 slowest. The initramfs size is about 33% smaller with LZMA in 175 comparison to gzip. 176 177 If you choose this, keep in mind that you may need to install the xz 178 or lzma tools to be able to compress the initram. 179 180config INITRAMFS_COMPRESSION_XZ 181 bool "XZ" 182 depends on RD_XZ 183 help 184 XZ uses the LZMA2 algorithm and has a large dictionary which may cause 185 problems on memory constrained systems. The initramfs size is about 186 30% smaller with XZ in comparison to gzip. Decompression speed is 187 better than that of bzip2 but worse than gzip and LZO. Compression is 188 slow. 189 190 If you choose this, keep in mind that you may need to install the xz 191 tool to be able to compress the initram. 192 193config INITRAMFS_COMPRESSION_LZO 194 bool "LZO" 195 depends on RD_LZO 196 help 197 It's compression ratio is the second poorest amongst the choices. The 198 kernel size is about 10% bigger than gzip. Despite that, it's 199 decompression speed is the second fastest and it's compression speed 200 is quite fast too. 201 202 If you choose this, keep in mind that you may need to install the lzop 203 tool to be able to compress the initram. 204 205config INITRAMFS_COMPRESSION_LZ4 206 bool "LZ4" 207 depends on RD_LZ4 208 help 209 It's compression ratio is the poorest amongst the choices. The kernel 210 size is about 15% bigger than gzip; however its decompression speed 211 is the fastest. 212 213 If you choose this, keep in mind that most distros don't provide lz4 214 by default which could cause a build failure. 215 216endchoice 217 218config INITRAMFS_COMPRESSION 219 depends on INITRAMFS_SOURCE!="" 220 string 221 default "" if INITRAMFS_COMPRESSION_NONE 222 default ".gz" if INITRAMFS_COMPRESSION_GZIP 223 default ".bz2" if INITRAMFS_COMPRESSION_BZIP2 224 default ".lzma" if INITRAMFS_COMPRESSION_LZMA 225 default ".xz" if INITRAMFS_COMPRESSION_XZ 226 default ".lzo" if INITRAMFS_COMPRESSION_LZO 227 default ".lz4" if INITRAMFS_COMPRESSION_LZ4 228 default ".gz" if RD_GZIP 229 default ".lz4" if RD_LZ4 230 default ".lzo" if RD_LZO 231 default ".xz" if RD_XZ 232 default ".lzma" if RD_LZMA 233 default ".bz2" if RD_BZIP2 234 default "" 235