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 This setting is only meaningful if the INITRAMFS_SOURCE is 40 contains a directory. Setting this user ID (UID) to something 41 other than "0" will cause all files owned by that UID to be 42 owned by user root in the initial ramdisk image. 43 44 If you are not sure, leave it set to "0". 45 46config INITRAMFS_ROOT_GID 47 int "Group ID to map to 0 (group root)" 48 depends on INITRAMFS_SOURCE!="" 49 default "0" 50 help 51 This setting is only meaningful if the INITRAMFS_SOURCE is 52 contains a directory. Setting this group ID (GID) to something 53 other than "0" will cause all files owned by that GID to be 54 owned by group root in the initial ramdisk image. 55 56 If you are not sure, leave it set to "0". 57 58config RD_GZIP 59 bool "Support initial ramdisks compressed using gzip" 60 depends on BLK_DEV_INITRD 61 default y 62 select DECOMPRESS_GZIP 63 help 64 Support loading of a gzip encoded initial ramdisk or cpio buffer. 65 If unsure, say Y. 66 67config RD_BZIP2 68 bool "Support initial ramdisks compressed using bzip2" 69 default y 70 depends on BLK_DEV_INITRD 71 select DECOMPRESS_BZIP2 72 help 73 Support loading of a bzip2 encoded initial ramdisk or cpio buffer 74 If unsure, say N. 75 76config RD_LZMA 77 bool "Support initial ramdisks compressed using LZMA" 78 default y 79 depends on BLK_DEV_INITRD 80 select DECOMPRESS_LZMA 81 help 82 Support loading of a LZMA encoded initial ramdisk or cpio buffer 83 If unsure, say N. 84 85config RD_XZ 86 bool "Support initial ramdisks compressed using XZ" 87 depends on BLK_DEV_INITRD 88 default y 89 select DECOMPRESS_XZ 90 help 91 Support loading of a XZ encoded initial ramdisk or cpio buffer. 92 If unsure, say N. 93 94config RD_LZO 95 bool "Support initial ramdisks compressed using LZO" 96 default y 97 depends on BLK_DEV_INITRD 98 select DECOMPRESS_LZO 99 help 100 Support loading of a LZO encoded initial ramdisk or cpio buffer 101 If unsure, say N. 102 103config RD_LZ4 104 bool "Support initial ramdisks compressed using LZ4" 105 default y 106 depends on BLK_DEV_INITRD 107 select DECOMPRESS_LZ4 108 help 109 Support loading of a LZ4 encoded initial ramdisk or cpio buffer 110 If unsure, say N. 111 112choice 113 prompt "Built-in initramfs compression mode" 114 depends on INITRAMFS_SOURCE!="" 115 optional 116 help 117 This option allows you to decide by which algorithm the builtin 118 initramfs will be compressed. Several compression algorithms are 119 available, which differ in efficiency, compression and 120 decompression speed. Compression speed is only relevant 121 when building a kernel. Decompression speed is relevant at 122 each boot. Also the memory usage during decompression may become 123 relevant on memory constrained systems. This is usually based on the 124 dictionary size of the algorithm with algorithms like XZ and LZMA 125 featuring large dictionary sizes. 126 127 High compression options are mostly useful for users who are 128 low on RAM, since it reduces the memory consumption during 129 boot. 130 131 Keep in mind that your build system needs to provide the appropriate 132 compression tool to compress the generated initram cpio file for 133 embedding. 134 135 If in doubt, select 'None' 136 137config INITRAMFS_COMPRESSION_NONE 138 bool "None" 139 help 140 Do not compress the built-in initramfs at all. This may sound wasteful 141 in space, but, you should be aware that the built-in initramfs will be 142 compressed at a later stage anyways along with the rest of the kernel, 143 on those architectures that support this. However, not compressing the 144 initramfs may lead to slightly higher memory consumption during a 145 short time at boot, while both the cpio image and the unpacked 146 filesystem image will be present in memory simultaneously 147 148config INITRAMFS_COMPRESSION_GZIP 149 bool "Gzip" 150 depends on RD_GZIP 151 help 152 Use the old and well tested gzip compression algorithm. Gzip provides 153 a good balance between compression ratio and decompression speed and 154 has a reasonable compression speed. It is also more likely to be 155 supported by your build system as the gzip tool is present by default 156 on most distros. 157 158config INITRAMFS_COMPRESSION_BZIP2 159 bool "Bzip2" 160 depends on RD_BZIP2 161 help 162 It's compression ratio and speed is intermediate. Decompression speed 163 is slowest among the choices. The initramfs size is about 10% smaller 164 with bzip2, in comparison to gzip. Bzip2 uses a large amount of 165 memory. For modern kernels you will need at least 8MB RAM or more for 166 booting. 167 168 If you choose this, keep in mind that you need to have the bzip2 tool 169 available to be able to compress the initram. 170 171config INITRAMFS_COMPRESSION_LZMA 172 bool "LZMA" 173 depends on RD_LZMA 174 help 175 This algorithm's compression ratio is best but has a large dictionary 176 size which might cause issues in memory constrained systems. 177 Decompression speed is between the other choices. Compression is 178 slowest. The initramfs size is about 33% smaller with LZMA in 179 comparison to gzip. 180 181 If you choose this, keep in mind that you may need to install the xz 182 or lzma tools to be able to compress the initram. 183 184config INITRAMFS_COMPRESSION_XZ 185 bool "XZ" 186 depends on RD_XZ 187 help 188 XZ uses the LZMA2 algorithm and has a large dictionary which may cause 189 problems on memory constrained systems. The initramfs size is about 190 30% smaller with XZ in comparison to gzip. Decompression speed is 191 better than that of bzip2 but worse than gzip and LZO. Compression is 192 slow. 193 194 If you choose this, keep in mind that you may need to install the xz 195 tool to be able to compress the initram. 196 197config INITRAMFS_COMPRESSION_LZO 198 bool "LZO" 199 depends on RD_LZO 200 help 201 It's compression ratio is the second poorest amongst the choices. The 202 kernel size is about 10% bigger than gzip. Despite that, it's 203 decompression speed is the second fastest and it's compression speed 204 is quite fast too. 205 206 If you choose this, keep in mind that you may need to install the lzop 207 tool to be able to compress the initram. 208 209config INITRAMFS_COMPRESSION_LZ4 210 bool "LZ4" 211 depends on RD_LZ4 212 help 213 It's compression ratio is the poorest amongst the choices. The kernel 214 size is about 15% bigger than gzip; however its decompression speed 215 is the fastest. 216 217 If you choose this, keep in mind that most distros don't provide lz4 218 by default which could cause a build failure. 219 220endchoice 221 222config INITRAMFS_COMPRESSION 223 depends on INITRAMFS_SOURCE!="" 224 string 225 default "" if INITRAMFS_COMPRESSION_NONE 226 default ".gz" if INITRAMFS_COMPRESSION_GZIP 227 default ".bz2" if INITRAMFS_COMPRESSION_BZIP2 228 default ".lzma" if INITRAMFS_COMPRESSION_LZMA 229 default ".xz" if INITRAMFS_COMPRESSION_XZ 230 default ".lzo" if INITRAMFS_COMPRESSION_LZO 231 default ".lz4" if INITRAMFS_COMPRESSION_LZ4 232 default ".gz" if RD_GZIP 233 default ".lz4" if RD_LZ4 234 default ".lzo" if RD_LZO 235 default ".xz" if RD_XZ 236 default ".lzma" if RD_LZMA 237 default ".bz2" if RD_BZIP2 238 default "" 239