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