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1# SPDX-License-Identifier: GPL-2.0
2#
3# Configuration for initramfs
4#
5
6config INITRAMFS_SOURCE
7 string "Initramfs source file(s)"
8 default ""
9 help
10 This can be either a single cpio archive with a .cpio suffix or a
11 space-separated list of directories and files for building the
12 initramfs image. A cpio archive should contain a filesystem archive
13 to be used as an initramfs image. Directories should contain a
14 filesystem layout to be included in the initramfs image. Files
15 should contain entries according to the format described by the
16 "usr/gen_init_cpio" program in the kernel tree.
17
18 When multiple directories and files are specified then the
19 initramfs image will be the aggregate of all of them.
20
21 See <file:Documentation/driver-api/early-userspace/early_userspace_support.rst> for more details.
22
23 If you are not sure, leave it blank.
24
25config INITRAMFS_FORCE
26 bool "Ignore the initramfs passed by the bootloader"
27 depends on CMDLINE_EXTEND || CMDLINE_FORCE
28 help
29 This option causes the kernel to ignore the initramfs image
30 (or initrd image) passed to it by the bootloader. This is
31 analogous to CMDLINE_FORCE, which is found on some architectures,
32 and is useful if you cannot or don't want to change the image
33 your bootloader passes to the kernel.
34
35config INITRAMFS_ROOT_UID
36 int "User ID to map to 0 (user root)"
37 depends on INITRAMFS_SOURCE!=""
38 default "0"
39 help
40 If INITRAMFS_SOURCE points to a directory, files owned by this UID
41 (-1 = current user) will be owned by root in the resulting image.
42
43 If you are not sure, leave it set to "0".
44
45config INITRAMFS_ROOT_GID
46 int "Group ID to map to 0 (group root)"
47 depends on INITRAMFS_SOURCE!=""
48 default "0"
49 help
50 If INITRAMFS_SOURCE points to a directory, files owned by this GID
51 (-1 = current group) will be owned by root in the resulting image.
52
53 If you are not sure, leave it set to "0".
54
55config RD_GZIP
56 bool "Support initial ramdisk/ramfs compressed using gzip"
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 ramdisk/ramfs compressed using bzip2"
65 default y
66 select DECOMPRESS_BZIP2
67 help
68 Support loading of a bzip2 encoded initial ramdisk or cpio buffer
69 If unsure, say N.
70
71config RD_LZMA
72 bool "Support initial ramdisk/ramfs compressed using LZMA"
73 default y
74 select DECOMPRESS_LZMA
75 help
76 Support loading of a LZMA encoded initial ramdisk or cpio buffer
77 If unsure, say N.
78
79config RD_XZ
80 bool "Support initial ramdisk/ramfs compressed using XZ"
81 default y
82 select DECOMPRESS_XZ
83 help
84 Support loading of a XZ encoded initial ramdisk or cpio buffer.
85 If unsure, say N.
86
87config RD_LZO
88 bool "Support initial ramdisk/ramfs compressed using LZO"
89 default y
90 select DECOMPRESS_LZO
91 help
92 Support loading of a LZO encoded initial ramdisk or cpio buffer
93 If unsure, say N.
94
95config RD_LZ4
96 bool "Support initial ramdisk/ramfs compressed using LZ4"
97 default y
98 select DECOMPRESS_LZ4
99 help
100 Support loading of a LZ4 encoded initial ramdisk or cpio buffer
101 If unsure, say N.
102
103config RD_ZSTD
104 bool "Support initial ramdisk/ramfs compressed using ZSTD"
105 default y
106 depends on BLK_DEV_INITRD
107 select DECOMPRESS_ZSTD
108 help
109 Support loading of a ZSTD 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 help
116 This option allows you to decide by which algorithm the builtin
117 initramfs will be compressed. Several compression algorithms are
118 available, which differ in efficiency, compression and
119 decompression speed. Compression speed is only relevant
120 when building a kernel. Decompression speed is relevant at
121 each boot. Also the memory usage during decompression may become
122 relevant on memory constrained systems. This is usually based on the
123 dictionary size of the algorithm with algorithms like XZ and LZMA
124 featuring large dictionary sizes.
125
126 High compression options are mostly useful for users who are
127 low on RAM, since it reduces the memory consumption during
128 boot.
129
130 Keep in mind that your build system needs to provide the appropriate
131 compression tool to compress the generated initram cpio file for
132 embedding.
133
134 If in doubt, select 'None'
135
136config INITRAMFS_COMPRESSION_GZIP
137 bool "Gzip"
138 depends on RD_GZIP
139 help
140 Use the old and well tested gzip compression algorithm. Gzip provides
141 a good balance between compression ratio and decompression speed and
142 has a reasonable compression speed. It is also more likely to be
143 supported by your build system as the gzip tool is present by default
144 on most distros.
145
146config INITRAMFS_COMPRESSION_BZIP2
147 bool "Bzip2"
148 depends on RD_BZIP2
149 help
150 It's compression ratio and speed is intermediate. Decompression speed
151 is slowest among the choices. The initramfs size is about 10% smaller
152 with bzip2, in comparison to gzip. Bzip2 uses a large amount of
153 memory. For modern kernels you will need at least 8MB RAM or more for
154 booting.
155
156 If you choose this, keep in mind that you need to have the bzip2 tool
157 available to be able to compress the initram.
158
159config INITRAMFS_COMPRESSION_LZMA
160 bool "LZMA"
161 depends on RD_LZMA
162 help
163 This algorithm's compression ratio is best but has a large dictionary
164 size which might cause issues in memory constrained systems.
165 Decompression speed is between the other choices. Compression is
166 slowest. The initramfs size is about 33% smaller with LZMA in
167 comparison to gzip.
168
169 If you choose this, keep in mind that you may need to install the xz
170 or lzma tools to be able to compress the initram.
171
172config INITRAMFS_COMPRESSION_XZ
173 bool "XZ"
174 depends on RD_XZ
175 help
176 XZ uses the LZMA2 algorithm and has a large dictionary which may cause
177 problems on memory constrained systems. The initramfs size is about
178 30% smaller with XZ in comparison to gzip. Decompression speed is
179 better than that of bzip2 but worse than gzip and LZO. Compression is
180 slow.
181
182 If you choose this, keep in mind that you may need to install the xz
183 tool to be able to compress the initram.
184
185config INITRAMFS_COMPRESSION_LZO
186 bool "LZO"
187 depends on RD_LZO
188 help
189 It's compression ratio is the second poorest amongst the choices. The
190 kernel size is about 10% bigger than gzip. Despite that, it's
191 decompression speed is the second fastest and it's compression speed
192 is quite fast too.
193
194 If you choose this, keep in mind that you may need to install the lzop
195 tool to be able to compress the initram.
196
197config INITRAMFS_COMPRESSION_LZ4
198 bool "LZ4"
199 depends on RD_LZ4
200 help
201 It's compression ratio is the poorest amongst the choices. The kernel
202 size is about 15% bigger than gzip; however its decompression speed
203 is the fastest.
204
205 If you choose this, keep in mind that most distros don't provide lz4
206 by default which could cause a build failure.
207
208config INITRAMFS_COMPRESSION_ZSTD
209 bool "ZSTD"
210 depends on RD_ZSTD
211 help
212 ZSTD is a compression algorithm targeting intermediate compression
213 with fast decompression speed. It will compress better than GZIP and
214 decompress around the same speed as LZO, but slower than LZ4.
215
216 If you choose this, keep in mind that you may need to install the zstd
217 tool to be able to compress the initram.
218
219config INITRAMFS_COMPRESSION_NONE
220 bool "None"
221 help
222 Do not compress the built-in initramfs at all. This may sound wasteful
223 in space, but, you should be aware that the built-in initramfs will be
224 compressed at a later stage anyways along with the rest of the kernel,
225 on those architectures that support this. However, not compressing the
226 initramfs may lead to slightly higher memory consumption during a
227 short time at boot, while both the cpio image and the unpacked
228 filesystem image will be present in memory simultaneously
229
230endchoice
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" if EXPERT
50 default y
51 depends on BLK_DEV_INITRD
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" if EXPERT
59 default !EXPERT
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" if EXPERT
68 default !EXPERT
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" if EXPERT
77 default !EXPERT
78 depends on BLK_DEV_INITRD
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" if EXPERT
86 default !EXPERT
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
93choice
94 prompt "Built-in initramfs compression mode" if INITRAMFS_SOURCE!=""
95 help
96 This option decides by which algorithm the builtin initramfs
97 will be compressed. Several compression algorithms are
98 available, which differ in efficiency, compression and
99 decompression speed. Compression speed is only relevant
100 when building a kernel. Decompression speed is relevant at
101 each boot.
102
103 If you have any problems with bzip2 or LZMA compressed
104 initramfs, mail me (Alain Knaff) <alain@knaff.lu>.
105
106 High compression options are mostly useful for users who are
107 low on RAM, since it reduces the memory consumption during
108 boot.
109
110 If in doubt, select 'gzip'
111
112config INITRAMFS_COMPRESSION_NONE
113 bool "None"
114 help
115 Do not compress the built-in initramfs at all. This may
116 sound wasteful in space, but, you should be aware that the
117 built-in initramfs will be compressed at a later stage
118 anyways along with the rest of the kernel, on those
119 architectures that support this.
120 However, not compressing the initramfs may lead to slightly
121 higher memory consumption during a short time at boot, while
122 both the cpio image and the unpacked filesystem image will
123 be present in memory simultaneously
124
125config INITRAMFS_COMPRESSION_GZIP
126 bool "Gzip"
127 depends on RD_GZIP
128 help
129 The old and tried gzip compression. It provides a good balance
130 between compression ratio and decompression speed.
131
132config INITRAMFS_COMPRESSION_BZIP2
133 bool "Bzip2"
134 depends on RD_BZIP2
135 help
136 Its compression ratio and speed is intermediate.
137 Decompression speed is slowest among the four. The initramfs
138 size is about 10% smaller with bzip2, in comparison to gzip.
139 Bzip2 uses a large amount of memory. For modern kernels you
140 will need at least 8MB RAM or more for booting.
141
142config INITRAMFS_COMPRESSION_LZMA
143 bool "LZMA"
144 depends on RD_LZMA
145 help
146 The most recent compression algorithm.
147 Its ratio is best, decompression speed is between the other
148 three. Compression is slowest. The initramfs size is about 33%
149 smaller with LZMA in comparison to gzip.
150
151config INITRAMFS_COMPRESSION_XZ
152 bool "XZ"
153 depends on RD_XZ
154 help
155 XZ uses the LZMA2 algorithm. The initramfs size is about 30%
156 smaller with XZ in comparison to gzip. Decompression speed
157 is better than that of bzip2 but worse than gzip and LZO.
158 Compression is slow.
159
160config INITRAMFS_COMPRESSION_LZO
161 bool "LZO"
162 depends on RD_LZO
163 help
164 Its compression ratio is the poorest among the four. The kernel
165 size is about 10% bigger than gzip; however its speed
166 (both compression and decompression) is the fastest.
167
168endchoice