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