xref: /openbmc/linux/usr/Kconfig (revision f7d84fa7) 
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_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
34config INITRAMFS_ROOT_UID
35	int "User ID to map to 0 (user root)"
36	depends on INITRAMFS_SOURCE!=""
37	default "0"
38	help
39	  This setting is only meaningful if the INITRAMFS_SOURCE is
40	  contains a directory.  Setting this user ID (UID) to something
41	  other than "0" will cause all files owned by that UID to be
42	  owned by user root in the initial ramdisk image.
43
44	  If you are not sure, leave it set to "0".
45
46config INITRAMFS_ROOT_GID
47	int "Group ID to map to 0 (group root)"
48	depends on INITRAMFS_SOURCE!=""
49	default "0"
50	help
51	  This setting is only meaningful if the INITRAMFS_SOURCE is
52	  contains a directory.  Setting this group ID (GID) to something
53	  other than "0" will cause all files owned by that GID to be
54	  owned by group root in the initial ramdisk image.
55
56	  If you are not sure, leave it set to "0".
57
58config RD_GZIP
59	bool "Support initial ramdisks compressed using gzip"
60	depends on BLK_DEV_INITRD
61	default y
62	select DECOMPRESS_GZIP
63	help
64	  Support loading of a gzip encoded initial ramdisk or cpio buffer.
65	  If unsure, say Y.
66
67config RD_BZIP2
68	bool "Support initial ramdisks compressed using bzip2"
69	default y
70	depends on BLK_DEV_INITRD
71	select DECOMPRESS_BZIP2
72	help
73	  Support loading of a bzip2 encoded initial ramdisk or cpio buffer
74	  If unsure, say N.
75
76config RD_LZMA
77	bool "Support initial ramdisks compressed using LZMA"
78	default y
79	depends on BLK_DEV_INITRD
80	select DECOMPRESS_LZMA
81	help
82	  Support loading of a LZMA encoded initial ramdisk or cpio buffer
83	  If unsure, say N.
84
85config RD_XZ
86	bool "Support initial ramdisks compressed using XZ"
87	depends on BLK_DEV_INITRD
88	default y
89	select DECOMPRESS_XZ
90	help
91	  Support loading of a XZ encoded initial ramdisk or cpio buffer.
92	  If unsure, say N.
93
94config RD_LZO
95	bool "Support initial ramdisks compressed using LZO"
96	default y
97	depends on BLK_DEV_INITRD
98	select DECOMPRESS_LZO
99	help
100	  Support loading of a LZO encoded initial ramdisk or cpio buffer
101	  If unsure, say N.
102
103config RD_LZ4
104	bool "Support initial ramdisks compressed using LZ4"
105	default y
106	depends on BLK_DEV_INITRD
107	select DECOMPRESS_LZ4
108	help
109	  Support loading of a LZ4 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	optional
116	help
117	  This option allows you to decide by which algorithm the builtin
118	  initramfs will be compressed.  Several compression algorithms are
119	  available, which differ in efficiency, compression and
120	  decompression speed.  Compression speed is only relevant
121	  when building a kernel.  Decompression speed is relevant at
122	  each boot. Also the memory usage during decompression may become
123	  relevant on memory constrained systems. This is usually based on the
124	  dictionary size of the algorithm with algorithms like XZ and LZMA
125	  featuring large dictionary sizes.
126
127	  High compression options are mostly useful for users who are
128	  low on RAM, since it reduces the memory consumption during
129	  boot.
130
131	  Keep in mind that your build system needs to provide the appropriate
132	  compression tool to compress the generated initram cpio file for
133	  embedding.
134
135	  If in doubt, select 'None'
136
137config INITRAMFS_COMPRESSION_NONE
138	bool "None"
139	help
140	  Do not compress the built-in initramfs at all. This may sound wasteful
141	  in space, but, you should be aware that the built-in initramfs will be
142	  compressed at a later stage anyways along with the rest of the kernel,
143	  on those architectures that support this. However, not compressing the
144	  initramfs may lead to slightly higher memory consumption during a
145	  short time at boot, while both the cpio image and the unpacked
146	  filesystem image will be present in memory simultaneously
147
148config INITRAMFS_COMPRESSION_GZIP
149	bool "Gzip"
150	depends on RD_GZIP
151	help
152	  Use the old and well tested gzip compression algorithm. Gzip provides
153	  a good balance between compression ratio and decompression speed and
154	  has a reasonable compression speed. It is also more likely to be
155	  supported by your build system as the gzip tool is present by default
156	  on most distros.
157
158config INITRAMFS_COMPRESSION_BZIP2
159	bool "Bzip2"
160	depends on RD_BZIP2
161	help
162	  It's compression ratio and speed is intermediate. Decompression speed
163	  is slowest among the choices. The initramfs size is about 10% smaller
164	  with bzip2, in comparison to gzip. Bzip2 uses a large amount of
165	  memory. For modern kernels you will need at least 8MB RAM or more for
166	  booting.
167
168	  If you choose this, keep in mind that you need to have the bzip2 tool
169	  available to be able to compress the initram.
170
171config INITRAMFS_COMPRESSION_LZMA
172	bool "LZMA"
173	depends on RD_LZMA
174	help
175	  This algorithm's compression ratio is best but has a large dictionary
176	  size which might cause issues in memory constrained systems.
177	  Decompression speed is between the other choices. Compression is
178	  slowest. The initramfs size is about 33% smaller with LZMA in
179	  comparison to gzip.
180
181	  If you choose this, keep in mind that you may need to install the xz
182	  or lzma tools to be able to compress the initram.
183
184config INITRAMFS_COMPRESSION_XZ
185	bool "XZ"
186	depends on RD_XZ
187	help
188	  XZ uses the LZMA2 algorithm and has a large dictionary which may cause
189	  problems on memory constrained systems. The initramfs size is about
190	  30% smaller with XZ in comparison to gzip. Decompression speed is
191	  better than that of bzip2 but worse than gzip and LZO. Compression is
192	  slow.
193
194	  If you choose this, keep in mind that you may need to install the xz
195	  tool to be able to compress the initram.
196
197config INITRAMFS_COMPRESSION_LZO
198	bool "LZO"
199	depends on RD_LZO
200	help
201	  It's compression ratio is the second poorest amongst the choices. The
202	  kernel size is about 10% bigger than gzip. Despite that, it's
203	  decompression speed is the second fastest and it's compression speed
204	  is quite fast too.
205
206	  If you choose this, keep in mind that you may need to install the lzop
207	  tool to be able to compress the initram.
208
209config INITRAMFS_COMPRESSION_LZ4
210	bool "LZ4"
211	depends on RD_LZ4
212	help
213	  It's compression ratio is the poorest amongst the choices. The kernel
214	  size is about 15% bigger than gzip; however its decompression speed
215	  is the fastest.
216
217	  If you choose this, keep in mind that most distros don't provide lz4
218	  by default which could cause a build failure.
219
220endchoice
221
222config INITRAMFS_COMPRESSION
223	depends on INITRAMFS_SOURCE!=""
224	string
225	default ""      if INITRAMFS_COMPRESSION_NONE
226	default ".gz"   if INITRAMFS_COMPRESSION_GZIP
227	default ".bz2"  if INITRAMFS_COMPRESSION_BZIP2
228	default ".lzma" if INITRAMFS_COMPRESSION_LZMA
229	default ".xz"   if INITRAMFS_COMPRESSION_XZ
230	default ".lzo"  if INITRAMFS_COMPRESSION_LZO
231	default ".lz4"  if INITRAMFS_COMPRESSION_LZ4
232	default ".gz"   if RD_GZIP
233	default ".lz4"  if RD_LZ4
234	default ".lzo"  if RD_LZO
235	default ".xz"   if RD_XZ
236	default ".lzma" if RD_LZMA
237	default ".bz2"  if RD_BZIP2
238	default ""
239