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	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	  Its compression ratio is the second poorest amongst the choices. The
189	  kernel size is about 10% bigger than gzip. Despite that, its
190	  decompression speed is the second fastest and its 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