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

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