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_ROOT_UID 25 int "User ID to map to 0 (user root)" 26 depends on INITRAMFS_SOURCE!="" 27 default "0" 28 help 29 This setting is only meaningful if the INITRAMFS_SOURCE is 30 contains a directory. Setting this user ID (UID) to something 31 other than "0" will cause all files owned by that UID to be 32 owned by user root in the initial ramdisk image. 33 34 If you are not sure, leave it set to "0". 35 36config INITRAMFS_ROOT_GID 37 int "Group ID to map to 0 (group root)" 38 depends on INITRAMFS_SOURCE!="" 39 default "0" 40 help 41 This setting is only meaningful if the INITRAMFS_SOURCE is 42 contains a directory. Setting this group ID (GID) to something 43 other than "0" will cause all files owned by that GID to be 44 owned by group root in the initial ramdisk image. 45 46 If you are not sure, leave it set to "0". 47 48config RD_GZIP 49 bool "Support initial ramdisks compressed using gzip" 50 depends on BLK_DEV_INITRD 51 default y 52 select DECOMPRESS_GZIP 53 help 54 Support loading of a gzip encoded initial ramdisk or cpio buffer. 55 If unsure, say Y. 56 57config RD_BZIP2 58 bool "Support initial ramdisks compressed using bzip2" 59 default y 60 depends on BLK_DEV_INITRD 61 select DECOMPRESS_BZIP2 62 help 63 Support loading of a bzip2 encoded initial ramdisk or cpio buffer 64 If unsure, say N. 65 66config RD_LZMA 67 bool "Support initial ramdisks compressed using LZMA" 68 default y 69 depends on BLK_DEV_INITRD 70 select DECOMPRESS_LZMA 71 help 72 Support loading of a LZMA encoded initial ramdisk or cpio buffer 73 If unsure, say N. 74 75config RD_XZ 76 bool "Support initial ramdisks compressed using XZ" 77 depends on BLK_DEV_INITRD 78 default y 79 select DECOMPRESS_XZ 80 help 81 Support loading of a XZ encoded initial ramdisk or cpio buffer. 82 If unsure, say N. 83 84config RD_LZO 85 bool "Support initial ramdisks compressed using LZO" 86 default y 87 depends on BLK_DEV_INITRD 88 select DECOMPRESS_LZO 89 help 90 Support loading of a LZO encoded initial ramdisk or cpio buffer 91 If unsure, say N. 92 93config RD_LZ4 94 bool "Support initial ramdisks compressed using LZ4" 95 default y 96 depends on BLK_DEV_INITRD 97 select DECOMPRESS_LZ4 98 help 99 Support loading of a LZ4 encoded initial ramdisk or cpio buffer 100 If unsure, say N. 101 102choice 103 prompt "Built-in initramfs compression mode" 104 depends on INITRAMFS_SOURCE!="" 105 optional 106 help 107 This option allows you to decide by which algorithm the builtin 108 initramfs will be compressed. Several compression algorithms are 109 available, which differ in efficiency, compression and 110 decompression speed. Compression speed is only relevant 111 when building a kernel. Decompression speed is relevant at 112 each boot. Also the memory usage during decompression may become 113 relevant on memory constrained systems. This is usually based on the 114 dictionary size of the algorithm with algorithms like XZ and LZMA 115 featuring large dictionary sizes. 116 117 High compression options are mostly useful for users who are 118 low on RAM, since it reduces the memory consumption during 119 boot. 120 121 Keep in mind that your build system needs to provide the appropriate 122 compression tool to compress the generated initram cpio file for 123 embedding. 124 125 If in doubt, select 'None' 126 127config INITRAMFS_COMPRESSION_NONE 128 bool "None" 129 help 130 Do not compress the built-in initramfs at all. This may sound wasteful 131 in space, but, you should be aware that the built-in initramfs will be 132 compressed at a later stage anyways along with the rest of the kernel, 133 on those architectures that support this. However, not compressing the 134 initramfs may lead to slightly higher memory consumption during a 135 short time at boot, while both the cpio image and the unpacked 136 filesystem image will be present in memory simultaneously 137 138config INITRAMFS_COMPRESSION_GZIP 139 bool "Gzip" 140 depends on RD_GZIP 141 help 142 Use the old and well tested gzip compression algorithm. Gzip provides 143 a good balance between compression ratio and decompression speed and 144 has a reasonable compression speed. It is also more likely to be 145 supported by your build system as the gzip tool is present by default 146 on most distros. 147 148config INITRAMFS_COMPRESSION_BZIP2 149 bool "Bzip2" 150 depends on RD_BZIP2 151 help 152 It's compression ratio and speed is intermediate. Decompression speed 153 is slowest among the choices. The initramfs size is about 10% smaller 154 with bzip2, in comparison to gzip. Bzip2 uses a large amount of 155 memory. For modern kernels you will need at least 8MB RAM or more for 156 booting. 157 158 If you choose this, keep in mind that you need to have the bzip2 tool 159 available to be able to compress the initram. 160 161config INITRAMFS_COMPRESSION_LZMA 162 bool "LZMA" 163 depends on RD_LZMA 164 help 165 This algorithm's compression ratio is best but has a large dictionary 166 size which might cause issues in memory constrained systems. 167 Decompression speed is between the other choices. Compression is 168 slowest. The initramfs size is about 33% smaller with LZMA in 169 comparison to gzip. 170 171 If you choose this, keep in mind that you may need to install the xz 172 or lzma tools to be able to compress the initram. 173 174config INITRAMFS_COMPRESSION_XZ 175 bool "XZ" 176 depends on RD_XZ 177 help 178 XZ uses the LZMA2 algorithm and has a large dictionary which may cause 179 problems on memory constrained systems. The initramfs size is about 180 30% smaller with XZ in comparison to gzip. Decompression speed is 181 better than that of bzip2 but worse than gzip and LZO. Compression is 182 slow. 183 184 If you choose this, keep in mind that you may need to install the xz 185 tool to be able to compress the initram. 186 187config INITRAMFS_COMPRESSION_LZO 188 bool "LZO" 189 depends on RD_LZO 190 help 191 It's compression ratio is the second poorest amongst the choices. The 192 kernel size is about 10% bigger than gzip. Despite that, it's 193 decompression speed is the second fastest and it's compression speed 194 is quite fast too. 195 196 If you choose this, keep in mind that you may need to install the lzop 197 tool to be able to compress the initram. 198 199config INITRAMFS_COMPRESSION_LZ4 200 bool "LZ4" 201 depends on RD_LZ4 202 help 203 It's compression ratio is the poorest amongst the choices. The kernel 204 size is about 15% bigger than gzip; however its decompression speed 205 is the fastest. 206 207 If you choose this, keep in mind that most distros don't provide lz4 208 by default which could cause a build failure. 209 210endchoice 211 212config INITRAMFS_COMPRESSION 213 string 214 default "" if INITRAMFS_COMPRESSION_NONE 215 default ".gz" if INITRAMFS_COMPRESSION_GZIP 216 default ".bz2" if INITRAMFS_COMPRESSION_BZIP2 217 default ".lzma" if INITRAMFS_COMPRESSION_LZMA 218 default ".xz" if INITRAMFS_COMPRESSION_XZ 219 default ".lzo" if INITRAMFS_COMPRESSION_LZO 220 default ".lz4" if INITRAMFS_COMPRESSION_LZ4 221 default ".gz" if RD_GZIP 222 default ".lz4" if RD_LZ4 223 default ".lzo" if RD_LZO 224 default ".xz" if RD_XZ 225 default ".lzma" if RD_LZMA 226 default ".bz2" if RD_BZIP2 227 default "" 228