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1 #
2 # Configuration for initramfs
3 #
4
5 config 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
24 config INITRAMFS_FORCE
25 bool "Ignore the initramfs passed by the bootloader"
26 depends on CMDLINE_EXTEND || CMDLINE_FORCE
27 help
28 This option causes the kernel to ignore the initramfs image
29 (or initrd image) passed to it by the bootloader. This is
30 analogous to CMDLINE_FORCE, which is found on some architectures,
31 and is useful if you cannot or don't want to change the image
32 your bootloader passes to the kernel.
33
34 config INITRAMFS_ROOT_UID
35 int "User ID to map to 0 (user root)"
36 depends on INITRAMFS_SOURCE!=""
37 default "0"
38 help
39 If INITRAMFS_SOURCE points to a directory, files owned by this UID
40 (-1 = current user) will be owned by root in the resulting image.
41
42 If you are not sure, leave it set to "0".
43
44 config INITRAMFS_ROOT_GID
45 int "Group ID to map to 0 (group root)"
46 depends on INITRAMFS_SOURCE!=""
47 default "0"
48 help
49 If INITRAMFS_SOURCE points to a directory, files owned by this GID
50 (-1 = current group) will be owned by root in the resulting image.
51
52 If you are not sure, leave it set to "0".
53
54 config RD_GZIP
55 bool "Support initial ramdisk/ramfs compressed using gzip"
56 depends on BLK_DEV_INITRD
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
63 config RD_BZIP2
64 bool "Support initial ramdisk/ramfs compressed using bzip2"
65 default y
66 depends on BLK_DEV_INITRD
67 select DECOMPRESS_BZIP2
68 help
69 Support loading of a bzip2 encoded initial ramdisk or cpio buffer
70 If unsure, say N.
71
72 config RD_LZMA
73 bool "Support initial ramdisk/ramfs compressed using LZMA"
74 default y
75 depends on BLK_DEV_INITRD
76 select DECOMPRESS_LZMA
77 help
78 Support loading of a LZMA encoded initial ramdisk or cpio buffer
79 If unsure, say N.
80
81 config RD_XZ
82 bool "Support initial ramdisk/ramfs compressed using XZ"
83 depends on BLK_DEV_INITRD
84 default y
85 select DECOMPRESS_XZ
86 help
87 Support loading of a XZ encoded initial ramdisk or cpio buffer.
88 If unsure, say N.
89
90 config RD_LZO
91 bool "Support initial ramdisk/ramfs compressed using LZO"
92 default y
93 depends on BLK_DEV_INITRD
94 select DECOMPRESS_LZO
95 help
96 Support loading of a LZO encoded initial ramdisk or cpio buffer
97 If unsure, say N.
98
99 config RD_LZ4
100 bool "Support initial ramdisk/ramfs compressed using LZ4"
101 default y
102 depends on BLK_DEV_INITRD
103 select DECOMPRESS_LZ4
104 help
105 Support loading of a LZ4 encoded initial ramdisk or cpio buffer
106 If unsure, say N.
107
108 choice
109 prompt "Built-in initramfs compression mode"
110 depends on INITRAMFS_SOURCE!=""
111 optional
112 help
113 This option allows you to decide by which algorithm the builtin
114 initramfs will be compressed. Several compression algorithms are
115 available, which differ in efficiency, compression and
116 decompression speed. Compression speed is only relevant
117 when building a kernel. Decompression speed is relevant at
118 each boot. Also the memory usage during decompression may become
119 relevant on memory constrained systems. This is usually based on the
120 dictionary size of the algorithm with algorithms like XZ and LZMA
121 featuring large dictionary sizes.
122
123 High compression options are mostly useful for users who are
124 low on RAM, since it reduces the memory consumption during
125 boot.
126
127 Keep in mind that your build system needs to provide the appropriate
128 compression tool to compress the generated initram cpio file for
129 embedding.
130
131 If in doubt, select 'None'
132
133 config INITRAMFS_COMPRESSION_NONE
134 bool "None"
135 help
136 Do not compress the built-in initramfs at all. This may sound wasteful
137 in space, but, you should be aware that the built-in initramfs will be
138 compressed at a later stage anyways along with the rest of the kernel,
139 on those architectures that support this. However, not compressing the
140 initramfs may lead to slightly higher memory consumption during a
141 short time at boot, while both the cpio image and the unpacked
142 filesystem image will be present in memory simultaneously
143
144 config INITRAMFS_COMPRESSION_GZIP
145 bool "Gzip"
146 depends on RD_GZIP
147 help
148 Use the old and well tested gzip compression algorithm. Gzip provides
149 a good balance between compression ratio and decompression speed and
150 has a reasonable compression speed. It is also more likely to be
151 supported by your build system as the gzip tool is present by default
152 on most distros.
153
154 config INITRAMFS_COMPRESSION_BZIP2
155 bool "Bzip2"
156 depends on RD_BZIP2
157 help
158 It's compression ratio and speed is intermediate. Decompression speed
159 is slowest among the choices. The initramfs size is about 10% smaller
160 with bzip2, in comparison to gzip. Bzip2 uses a large amount of
161 memory. For modern kernels you will need at least 8MB RAM or more for
162 booting.
163
164 If you choose this, keep in mind that you need to have the bzip2 tool
165 available to be able to compress the initram.
166
167 config INITRAMFS_COMPRESSION_LZMA
168 bool "LZMA"
169 depends on RD_LZMA
170 help
171 This algorithm's compression ratio is best but has a large dictionary
172 size which might cause issues in memory constrained systems.
173 Decompression speed is between the other choices. Compression is
174 slowest. The initramfs size is about 33% smaller with LZMA in
175 comparison to gzip.
176
177 If you choose this, keep in mind that you may need to install the xz
178 or lzma tools to be able to compress the initram.
179
180 config INITRAMFS_COMPRESSION_XZ
181 bool "XZ"
182 depends on RD_XZ
183 help
184 XZ uses the LZMA2 algorithm and has a large dictionary which may cause
185 problems on memory constrained systems. The initramfs size is about
186 30% smaller with XZ in comparison to gzip. Decompression speed is
187 better than that of bzip2 but worse than gzip and LZO. Compression is
188 slow.
189
190 If you choose this, keep in mind that you may need to install the xz
191 tool to be able to compress the initram.
192
193 config INITRAMFS_COMPRESSION_LZO
194 bool "LZO"
195 depends on RD_LZO
196 help
197 It's compression ratio is the second poorest amongst the choices. The
198 kernel size is about 10% bigger than gzip. Despite that, it's
199 decompression speed is the second fastest and it's compression speed
200 is quite fast too.
201
202 If you choose this, keep in mind that you may need to install the lzop
203 tool to be able to compress the initram.
204
205 config INITRAMFS_COMPRESSION_LZ4
206 bool "LZ4"
207 depends on RD_LZ4
208 help
209 It's compression ratio is the poorest amongst the choices. The kernel
210 size is about 15% bigger than gzip; however its decompression speed
211 is the fastest.
212
213 If you choose this, keep in mind that most distros don't provide lz4
214 by default which could cause a build failure.
215
216 endchoice
217
218 config INITRAMFS_COMPRESSION
219 depends on INITRAMFS_SOURCE!=""
220 string
221 default "" if INITRAMFS_COMPRESSION_NONE
222 default ".gz" if INITRAMFS_COMPRESSION_GZIP
223 default ".bz2" if INITRAMFS_COMPRESSION_BZIP2
224 default ".lzma" if INITRAMFS_COMPRESSION_LZMA
225 default ".xz" if INITRAMFS_COMPRESSION_XZ
226 default ".lzo" if INITRAMFS_COMPRESSION_LZO
227 default ".lz4" if INITRAMFS_COMPRESSION_LZ4
228 default ".gz" if RD_GZIP
229 default ".lz4" if RD_LZ4
230 default ".lzo" if RD_LZO
231 default ".xz" if RD_XZ
232 default ".lzma" if RD_LZMA
233 default ".bz2" if RD_BZIP2
234 default ""