1
2
3
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 select DECOMPRESS_ZSTD
107 help
108 Support loading of a ZSTD encoded initial ramdisk or cpio buffer.
109 If unsure, say N.
110
111choice
112 prompt "Built-in initramfs compression mode"
113 depends on INITRAMFS_SOURCE != ""
114 help
115 This option allows you to decide by which algorithm the builtin
116 initramfs will be compressed. Several compression algorithms are
117 available, which differ in efficiency, compression and
118 decompression speed. Compression speed is only relevant
119 when building a kernel. Decompression speed is relevant at
120 each boot. Also the memory usage during decompression may become
121 relevant on memory constrained systems. This is usually based on the
122 dictionary size of the algorithm with algorithms like XZ and LZMA
123 featuring large dictionary sizes.
124
125 High compression options are mostly useful for users who are
126 low on RAM, since it reduces the memory consumption during
127 boot.
128
129 Keep in mind that your build system needs to provide the appropriate
130 compression tool to compress the generated initram cpio file for
131 embedding.
132
133 If in doubt, select 'None'
134
135config INITRAMFS_COMPRESSION_GZIP
136 bool "Gzip"
137 depends on RD_GZIP
138 help
139 Use the old and well tested gzip compression algorithm. Gzip provides
140 a good balance between compression ratio and decompression speed and
141 has a reasonable compression speed. It is also more likely to be
142 supported by your build system as the gzip tool is present by default
143 on most distros.
144
145config INITRAMFS_COMPRESSION_BZIP2
146 bool "Bzip2"
147 depends on RD_BZIP2
148 help
149 It's compression ratio and speed is intermediate. Decompression speed
150 is slowest among the choices. The initramfs size is about 10% smaller
151 with bzip2, in comparison to gzip. Bzip2 uses a large amount of
152 memory. For modern kernels you will need at least 8MB RAM or more for
153 booting.
154
155 If you choose this, keep in mind that you need to have the bzip2 tool
156 available to be able to compress the initram.
157
158config INITRAMFS_COMPRESSION_LZMA
159 bool "LZMA"
160 depends on RD_LZMA
161 help
162 This algorithm's compression ratio is best but has a large dictionary
163 size which might cause issues in memory constrained systems.
164 Decompression speed is between the other choices. Compression is
165 slowest. The initramfs size is about 33% smaller with LZMA in
166 comparison to gzip.
167
168 If you choose this, keep in mind that you may need to install the xz
169 or lzma tools to be able to compress the initram.
170
171config INITRAMFS_COMPRESSION_XZ
172 bool "XZ"
173 depends on RD_XZ
174 help
175 XZ uses the LZMA2 algorithm and has a large dictionary which may cause
176 problems on memory constrained systems. The initramfs size is about
177 30% smaller with XZ in comparison to gzip. Decompression speed is
178 better than that of bzip2 but worse than gzip and LZO. Compression is
179 slow.
180
181 If you choose this, keep in mind that you may need to install the xz
182 tool to be able to compress the initram.
183
184config INITRAMFS_COMPRESSION_LZO
185 bool "LZO"
186 depends on RD_LZO
187 help
188 It's compression ratio is the second poorest amongst the choices. The
189 kernel size is about 10% bigger than gzip. Despite that, it's
190 decompression speed is the second fastest and it's compression speed
191 is quite fast too.
192
193 If you choose this, keep in mind that you may need to install the lzop
194 tool to be able to compress the initram.
195
196config INITRAMFS_COMPRESSION_LZ4
197 bool "LZ4"
198 depends on RD_LZ4
199 help
200 It's compression ratio is the poorest amongst the choices. The kernel
201 size is about 15% bigger than gzip; however its decompression speed
202 is the fastest.
203
204 If you choose this, keep in mind that most distros don't provide lz4
205 by default which could cause a build failure.
206
207config INITRAMFS_COMPRESSION_ZSTD
208 bool "ZSTD"
209 depends on RD_ZSTD
210 help
211 ZSTD is a compression algorithm targeting intermediate compression
212 with fast decompression speed. It will compress better than GZIP and
213 decompress around the same speed as LZO, but slower than LZ4.
214
215 If you choose this, keep in mind that you may need to install the zstd
216 tool to be able to compress the initram.
217
218config INITRAMFS_COMPRESSION_NONE
219 bool "None"
220 help
221 Do not compress the built-in initramfs at all. This may sound wasteful
222 in space, but, you should be aware that the built-in initramfs will be
223 compressed at a later stage anyways along with the rest of the kernel,
224 on those architectures that support this. However, not compressing the
225 initramfs may lead to slightly higher memory consumption during a
226 short time at boot, while both the cpio image and the unpacked
227 filesystem image will be present in memory simultaneously
228
229endchoice
230
