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Linux/usr/Kconfig

  1 #
  2 # Configuration for initramfs
  3 #
  4 
  5 config 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 
 24 config 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 
 36 config 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 
 48 config 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 
 57 config 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 
 66 config 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 
 75 config 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 
 84 config 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 
 93 config RD_LZ4
 94         bool "Support initial ramdisks compressed using LZ4" if EXPERT
 95         default !EXPERT
 96         depends on BLK_DEV_INITRD
 97         select DECOMPRESS_LZ4
 98         help
 99           Support loading of a LZ4 encoded initial ramdisk or cpio buffer
100           If unsure, say N.
101 
102 choice
103         prompt "Built-in initramfs compression mode" if INITRAMFS_SOURCE!=""
104         help
105           This option decides by which algorithm the builtin initramfs
106           will be compressed.  Several compression algorithms are
107           available, which differ in efficiency, compression and
108           decompression speed.  Compression speed is only relevant
109           when building a kernel.  Decompression speed is relevant at
110           each boot.
111 
112           If you have any problems with bzip2 or LZMA compressed
113           initramfs, mail me (Alain Knaff) <alain@knaff.lu>.
114 
115           High compression options are mostly useful for users who are
116           low on RAM, since it reduces the memory consumption during
117           boot.
118 
119           If in doubt, select 'gzip'
120 
121 config INITRAMFS_COMPRESSION_NONE
122         bool "None"
123         help
124           Do not compress the built-in initramfs at all. This may
125           sound wasteful in space, but, you should be aware that the
126           built-in initramfs will be compressed at a later stage
127           anyways along with the rest of the kernel, on those
128           architectures that support this.
129           However, not compressing the initramfs may lead to slightly
130           higher memory consumption during a short time at boot, while
131           both the cpio image and the unpacked filesystem image will
132           be present in memory simultaneously
133 
134 config INITRAMFS_COMPRESSION_GZIP
135         bool "Gzip"
136         depends on RD_GZIP
137         help
138           The old and tried gzip compression. It provides a good balance
139           between compression ratio and decompression speed.
140 
141 config INITRAMFS_COMPRESSION_BZIP2
142         bool "Bzip2"
143         depends on RD_BZIP2
144         help
145           Its compression ratio and speed is intermediate.
146           Decompression speed is slowest among the choices.  The initramfs
147           size is about 10% smaller with bzip2, in comparison to gzip.
148           Bzip2 uses a large amount of memory. For modern kernels you
149           will need at least 8MB RAM or more for booting.
150 
151 config INITRAMFS_COMPRESSION_LZMA
152         bool "LZMA"
153         depends on RD_LZMA
154         help
155           This algorithm's compression ratio is best.
156           Decompression speed is between the other choices.
157           Compression is slowest. The initramfs size is about 33%
158           smaller with LZMA in comparison to gzip.
159 
160 config INITRAMFS_COMPRESSION_XZ
161         bool "XZ"
162         depends on RD_XZ
163         help
164           XZ uses the LZMA2 algorithm. The initramfs size is about 30%
165           smaller with XZ in comparison to gzip. Decompression speed
166           is better than that of bzip2 but worse than gzip and LZO.
167           Compression is slow.
168 
169 config INITRAMFS_COMPRESSION_LZO
170         bool "LZO"
171         depends on RD_LZO
172         help
173           Its compression ratio is the poorest among the choices. The kernel
174           size is about 10% bigger than gzip; however its speed
175           (both compression and decompression) is the fastest.
176 
177 endchoice

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