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 EXPERT
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 EXPERT
59    default !EXPERT
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 EXPERT
68    default !EXPERT
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_XZ
76    bool "Support initial ramdisks compressed using XZ" if EXPERT
77    default !EXPERT
78    depends on BLK_DEV_INITRD
79    select DECOMPRESS_XZ
80    help
81      Support loading of a XZ encoded initial ramdisk or cpio buffer.
82      If unsure, say N.
83
84config RD_LZO
85    bool "Support initial ramdisks compressed using LZO" if EXPERT
86    default !EXPERT
87    depends on BLK_DEV_INITRD
88    select DECOMPRESS_LZO
89    help
90      Support loading of a LZO encoded initial ramdisk or cpio buffer
91      If unsure, say N.
92
93choice
94    prompt "Built-in initramfs compression mode" if INITRAMFS_SOURCE!=""
95    help
96      This option decides by which algorithm the builtin initramfs
97      will be compressed. Several compression algorithms are
98      available, which differ in efficiency, compression and
99      decompression speed. Compression speed is only relevant
100      when building a kernel. Decompression speed is relevant at
101      each boot.
102
103      If you have any problems with bzip2 or LZMA compressed
104      initramfs, mail me (Alain Knaff) <alain@knaff.lu>.
105
106      High compression options are mostly useful for users who are
107      low on RAM, since it reduces the memory consumption during
108      boot.
109
110      If in doubt, select 'gzip'
111
112config INITRAMFS_COMPRESSION_NONE
113    bool "None"
114    help
115      Do not compress the built-in initramfs at all. This may
116      sound wasteful in space, but, you should be aware that the
117      built-in initramfs will be compressed at a later stage
118      anyways along with the rest of the kernel, on those
119      architectures that support this.
120      However, not compressing the initramfs may lead to slightly
121      higher memory consumption during a short time at boot, while
122      both the cpio image and the unpacked filesystem image will
123      be present in memory simultaneously
124
125config INITRAMFS_COMPRESSION_GZIP
126    bool "Gzip"
127    depends on RD_GZIP
128    help
129      The old and tried gzip compression. It provides a good balance
130      between compression ratio and decompression speed.
131
132config INITRAMFS_COMPRESSION_BZIP2
133    bool "Bzip2"
134    depends on RD_BZIP2
135    help
136      Its compression ratio and speed is intermediate.
137      Decompression speed is slowest among the choices. The initramfs
138      size is about 10% smaller with bzip2, in comparison to gzip.
139      Bzip2 uses a large amount of memory. For modern kernels you
140      will need at least 8MB RAM or more for booting.
141
142config INITRAMFS_COMPRESSION_LZMA
143    bool "LZMA"
144    depends on RD_LZMA
145    help
146      This algorithm's compression ratio is best.
147      Decompression speed is between the other choices.
148      Compression is slowest. The initramfs size is about 33%
149      smaller with LZMA in comparison to gzip.
150
151config INITRAMFS_COMPRESSION_XZ
152    bool "XZ"
153    depends on RD_XZ
154    help
155      XZ uses the LZMA2 algorithm. The initramfs size is about 30%
156      smaller with XZ in comparison to gzip. Decompression speed
157      is better than that of bzip2 but worse than gzip and LZO.
158      Compression is slow.
159
160config INITRAMFS_COMPRESSION_LZO
161    bool "LZO"
162    depends on RD_LZO
163    help
164      Its compression ratio is the poorest among the choices. The kernel
165      size is about 10% bigger than gzip; however its speed
166      (both compression and decompression) is the fastest.
167
168endchoice
169

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