Root/usr/Kconfig

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_ROOT_UID
25    int "User ID to map to 0 (user root)"
26    depends on INITRAMFS_SOURCE!=""
27    default "0"
28    help
29      This setting is only meaningful if the INITRAMFS_SOURCE is
30      contains a directory. Setting this user ID (UID) to something
31      other than "0" will cause all files owned by that UID to be
32      owned by user root in the initial ramdisk image.
33
34      If you are not sure, leave it set to "0".
35
36config INITRAMFS_ROOT_GID
37    int "Group ID to map to 0 (group root)"
38    depends on INITRAMFS_SOURCE!=""
39    default "0"
40    help
41      This setting is only meaningful if the INITRAMFS_SOURCE is
42      contains a directory. Setting this group ID (GID) to something
43      other than "0" will cause all files owned by that GID to be
44      owned by group root in the initial ramdisk image.
45
46      If you are not sure, leave it set to "0".
47
48config RD_GZIP
49    bool "Support initial ramdisks compressed using gzip" if EMBEDDED
50    default y
51    depends on BLK_DEV_INITRD
52    select DECOMPRESS_GZIP
53    help
54      Support loading of a gzip encoded initial ramdisk or cpio buffer.
55      If unsure, say Y.
56
57config RD_BZIP2
58    bool "Support initial ramdisks compressed using bzip2" if EMBEDDED
59    default !EMBEDDED
60    depends on BLK_DEV_INITRD
61    select DECOMPRESS_BZIP2
62    help
63      Support loading of a bzip2 encoded initial ramdisk or cpio buffer
64      If unsure, say N.
65
66config RD_LZMA
67    bool "Support initial ramdisks compressed using LZMA" if EMBEDDED
68    default !EMBEDDED
69    depends on BLK_DEV_INITRD
70    select DECOMPRESS_LZMA
71    help
72      Support loading of a LZMA encoded initial ramdisk or cpio buffer
73      If unsure, say N.
74
75config RD_LZO
76    bool "Support initial ramdisks compressed using LZO" if EMBEDDED
77    default !EMBEDDED
78    depends on BLK_DEV_INITRD
79    select DECOMPRESS_LZO
80    help
81      Support loading of a LZO encoded initial ramdisk or cpio buffer
82      If unsure, say N.
83
84choice
85    prompt "Built-in initramfs compression mode" if INITRAMFS_SOURCE!=""
86    help
87      This option decides by which algorithm the builtin initramfs
88      will be compressed. Several compression algorithms are
89      available, which differ in efficiency, compression and
90      decompression speed. Compression speed is only relevant
91      when building a kernel. Decompression speed is relevant at
92      each boot.
93
94      If you have any problems with bzip2 or LZMA compressed
95      initramfs, mail me (Alain Knaff) <alain@knaff.lu>.
96
97      High compression options are mostly useful for users who are
98      low on RAM, since it reduces the memory consumption during
99      boot.
100
101      If in doubt, select 'gzip'
102
103config INITRAMFS_COMPRESSION_NONE
104    bool "None"
105    help
106      Do not compress the built-in initramfs at all. This may
107      sound wasteful in space, but, you should be aware that the
108      built-in initramfs will be compressed at a later stage
109      anyways along with the rest of the kernel, on those
110      architectures that support this.
111      However, not compressing the initramfs may lead to slightly
112      higher memory consumption during a short time at boot, while
113      both the cpio image and the unpacked filesystem image will
114      be present in memory simultaneously
115
116config INITRAMFS_COMPRESSION_GZIP
117    bool "Gzip"
118    depends on RD_GZIP
119    help
120      The old and tried gzip compression. It provides a good balance
121      between compression ratio and decompression speed.
122
123config INITRAMFS_COMPRESSION_BZIP2
124    bool "Bzip2"
125    depends on RD_BZIP2
126    help
127      Its compression ratio and speed is intermediate.
128      Decompression speed is slowest among the four. The initramfs
129      size is about 10% smaller with bzip2, in comparison to gzip.
130      Bzip2 uses a large amount of memory. For modern kernels you
131      will need at least 8MB RAM or more for booting.
132
133config INITRAMFS_COMPRESSION_LZMA
134    bool "LZMA"
135    depends on RD_LZMA
136    help
137      The most recent compression algorithm.
138      Its ratio is best, decompression speed is between the other
139      three. Compression is slowest. The initramfs size is about 33%
140      smaller with LZMA in comparison to gzip.
141
142config INITRAMFS_COMPRESSION_LZO
143    bool "LZO"
144    depends on RD_LZO
145    help
146      Its compression ratio is the poorest among the four. The kernel
147      size is about 10% bigger than gzip; however its speed
148      (both compression and decompression) is the fastest.
149
150endchoice
151

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