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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	depends on BLK_DEV_INITRD
58	default y
59	select DECOMPRESS_GZIP
60	help
61	  Support loading of a gzip encoded initial ramdisk or cpio buffer.
62	  If unsure, say Y.
63
64config RD_BZIP2
65	bool "Support initial ramdisk/ramfs compressed using bzip2"
66	default y
67	depends on BLK_DEV_INITRD
68	select DECOMPRESS_BZIP2
69	help
70	  Support loading of a bzip2 encoded initial ramdisk or cpio buffer
71	  If unsure, say N.
72
73config RD_LZMA
74	bool "Support initial ramdisk/ramfs compressed using LZMA"
75	default y
76	depends on BLK_DEV_INITRD
77	select DECOMPRESS_LZMA
78	help
79	  Support loading of a LZMA encoded initial ramdisk or cpio buffer
80	  If unsure, say N.
81
82config RD_XZ
83	bool "Support initial ramdisk/ramfs compressed using XZ"
84	depends on BLK_DEV_INITRD
85	default y
86	select DECOMPRESS_XZ
87	help
88	  Support loading of a XZ encoded initial ramdisk or cpio buffer.
89	  If unsure, say N.
90
91config RD_LZO
92	bool "Support initial ramdisk/ramfs compressed using LZO"
93	default y
94	depends on BLK_DEV_INITRD
95	select DECOMPRESS_LZO
96	help
97	  Support loading of a LZO encoded initial ramdisk or cpio buffer
98	  If unsure, say N.
99
100config RD_LZ4
101	bool "Support initial ramdisk/ramfs compressed using LZ4"
102	default y
103	depends on BLK_DEV_INITRD
104	select DECOMPRESS_LZ4
105	help
106	  Support loading of a LZ4 encoded initial ramdisk or cpio buffer
107	  If unsure, say N.
108
109choice
110	prompt "Built-in initramfs compression mode"
111	depends on INITRAMFS_SOURCE!=""
112	optional
113	help
114	  This option allows you to decide by which algorithm the builtin
115	  initramfs will be compressed.  Several compression algorithms are
116	  available, which differ in efficiency, compression and
117	  decompression speed.  Compression speed is only relevant
118	  when building a kernel.  Decompression speed is relevant at
119	  each boot. Also the memory usage during decompression may become
120	  relevant on memory constrained systems. This is usually based on the
121	  dictionary size of the algorithm with algorithms like XZ and LZMA
122	  featuring large dictionary sizes.
123
124	  High compression options are mostly useful for users who are
125	  low on RAM, since it reduces the memory consumption during
126	  boot.
127
128	  Keep in mind that your build system needs to provide the appropriate
129	  compression tool to compress the generated initram cpio file for
130	  embedding.
131
132	  If in doubt, select 'None'
133
134config INITRAMFS_COMPRESSION_NONE
135	bool "None"
136	help
137	  Do not compress the built-in initramfs at all. This may sound wasteful
138	  in space, but, you should be aware that the built-in initramfs will be
139	  compressed at a later stage anyways along with the rest of the kernel,
140	  on those architectures that support this. However, not compressing the
141	  initramfs may lead to slightly higher memory consumption during a
142	  short time at boot, while both the cpio image and the unpacked
143	  filesystem image will be present in memory simultaneously
144
145config INITRAMFS_COMPRESSION_GZIP
146	bool "Gzip"
147	depends on RD_GZIP
148	help
149	  Use the old and well tested gzip compression algorithm. Gzip provides
150	  a good balance between compression ratio and decompression speed and
151	  has a reasonable compression speed. It is also more likely to be
152	  supported by your build system as the gzip tool is present by default
153	  on most distros.
154
155config INITRAMFS_COMPRESSION_BZIP2
156	bool "Bzip2"
157	depends on RD_BZIP2
158	help
159	  It's compression ratio and speed is intermediate. Decompression speed
160	  is slowest among the choices. The initramfs size is about 10% smaller
161	  with bzip2, in comparison to gzip. Bzip2 uses a large amount of
162	  memory. For modern kernels you will need at least 8MB RAM or more for
163	  booting.
164
165	  If you choose this, keep in mind that you need to have the bzip2 tool
166	  available to be able to compress the initram.
167
168config INITRAMFS_COMPRESSION_LZMA
169	bool "LZMA"
170	depends on RD_LZMA
171	help
172	  This algorithm's compression ratio is best but has a large dictionary
173	  size which might cause issues in memory constrained systems.
174	  Decompression speed is between the other choices. Compression is
175	  slowest. The initramfs size is about 33% smaller with LZMA in
176	  comparison to gzip.
177
178	  If you choose this, keep in mind that you may need to install the xz
179	  or lzma tools to be able to compress the initram.
180
181config INITRAMFS_COMPRESSION_XZ
182	bool "XZ"
183	depends on RD_XZ
184	help
185	  XZ uses the LZMA2 algorithm and has a large dictionary which may cause
186	  problems on memory constrained systems. The initramfs size is about
187	  30% smaller with XZ in comparison to gzip. Decompression speed is
188	  better than that of bzip2 but worse than gzip and LZO. Compression is
189	  slow.
190
191	  If you choose this, keep in mind that you may need to install the xz
192	  tool to be able to compress the initram.
193
194config INITRAMFS_COMPRESSION_LZO
195	bool "LZO"
196	depends on RD_LZO
197	help
198	  It's compression ratio is the second poorest amongst the choices. The
199	  kernel size is about 10% bigger than gzip. Despite that, it's
200	  decompression speed is the second fastest and it's compression speed
201	  is quite fast too.
202
203	  If you choose this, keep in mind that you may need to install the lzop
204	  tool to be able to compress the initram.
205
206config INITRAMFS_COMPRESSION_LZ4
207	bool "LZ4"
208	depends on RD_LZ4
209	help
210	  It's compression ratio is the poorest amongst the choices. The kernel
211	  size is about 15% bigger than gzip; however its decompression speed
212	  is the fastest.
213
214	  If you choose this, keep in mind that most distros don't provide lz4
215	  by default which could cause a build failure.
216
217endchoice
218
219config INITRAMFS_COMPRESSION
220	depends on INITRAMFS_SOURCE!=""
221	string
222	default ""      if INITRAMFS_COMPRESSION_NONE
223	default ".gz"   if INITRAMFS_COMPRESSION_GZIP
224	default ".bz2"  if INITRAMFS_COMPRESSION_BZIP2
225	default ".lzma" if INITRAMFS_COMPRESSION_LZMA
226	default ".xz"   if INITRAMFS_COMPRESSION_XZ
227	default ".lzo"  if INITRAMFS_COMPRESSION_LZO
228	default ".lz4"  if INITRAMFS_COMPRESSION_LZ4
229	default ".gz"   if RD_GZIP
230	default ".lz4"  if RD_LZ4
231	default ".lzo"  if RD_LZO
232	default ".xz"   if RD_XZ
233	default ".lzma" if RD_LZMA
234	default ".bz2"  if RD_BZIP2
235	default ""
236