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32 .\" @(#)newfs.8 8.6 (Berkeley) 5/3/95
41 .Nd construct a new file system
45 .Op Fl S Ar sector-size
48 .Op Fl b Ar block-size
55 .Op Fl l Ar interleave
56 .Op Fl m Ar free space
57 .Op Fl n Ar rotational positions
58 .Op Fl o Ar optimization
60 .Op Fl r Ar revolutions
72 .Op Fl b Ar block-size
78 .Op Fl m Ar free space
79 .Op Fl n Ar rotational positions
85 replaces the more obtuse
92 the disk must be labeled using
95 builds a file system on the specified special file.
96 (We often refer to the
100 although the special file need not be a physical disk.
101 In fact, it need not even be special.)
102 Typically the defaults are reasonable, however
104 has numerous options to allow the defaults to be selectively overridden.
107 is used to build a file system in virtual memory and then mount it
110 exits and the contents of the file system are lost
111 when the file system is unmounted.
114 is sent a signal while running,
115 for example during system shutdown,
116 it will attempt to unmount its
117 corresponding file system.
120 are the same as those to
124 flag is specified (see below), the special file is unused.
125 Otherwise, it is only used to read the disk label which provides
126 a set of configuration parameters for the memory based file system.
127 The special file is typically that of the primary swap area,
128 since that is where the file system will be backed up when
129 free memory gets low and the memory supporting
130 the file system has to be paged.
132 The following options define the general layout policies:
133 .Bl -tag -width indent
135 For backward compatibility and for
139 will use this file for the image of the filesystem. When
141 exits, this file will be left behind.
143 Cause the file system parameters to be printed out
144 without really creating the file system.
149 This options is primarily used to build root filesystems
150 that can be understood by older boot ROMs.
152 Use information for the specified disk from
154 instead of trying to get the information from a disklabel.
155 .It Fl a Ar maxcontig
156 Specify the maximum number of contiguous blocks that will be
157 laid out before forcing a rotational delay (see the
160 The default value is 1.
163 for more details on how to set this option.
164 .It Fl b Ar block-size
165 The block size of the file system, in bytes. It must be a power of 2. The
166 default size is 8192 bytes, and the smallest allowable size is 4096 bytes.
167 .It Fl c Ar #cylinders/group
168 The number of cylinders per cylinder group in a file system. The default value
169 is 16. The maximum value is dependent on a number of other parameters, in
170 particular the block size. The best way to find the maximum value for a
171 specific file system is to attempt to specify a value which is far too large:
173 will print out the maximum value.
175 This parameter once specified the minimum time in milliseconds required to
176 initiate another disk transfer on the same cylinder. It was used in determining
177 the rotationally optimal layout for disk blocks within a file. Modern disks
178 with read/write-behind achieve higher performance with this feature disabled, so
179 this value should be left at the default value of 0 milliseconds. See
181 for more details on how to set this option.
184 Indicate the maximum number of blocks any single file can
185 allocate out of a cylinder group before it is forced to begin
186 allocating blocks from another cylinder group.
187 The default is about one quarter of the total blocks in a cylinder group.
190 for more details on how to set this option.
191 .It Fl f Ar frag-size
192 The fragment size of the file system in bytes. It must be a power of two
193 ranging in value between
197 The default is 1024 bytes.
198 .It Fl i Ar number of bytes per inode
199 Specify the density of inodes in the file system.
200 The default is to create an inode for every (4 * frag-size) bytes of data space.
201 If fewer inodes are desired, a larger number should be used;
202 to create more inodes a smaller number should be given.
203 One inode is required for each distinct file, so this value effectively
204 specifies the average file size on the file system.
205 .It Fl m Ar free space \&%
206 The percentage of space reserved from normal users; the minimum free
208 The default value used is
212 .Ao Pa ufs/ffs/fs.h Ac ,
216 for more details on how to set this option.
217 .It Fl n Ar number of distinguished rotational positions
218 UFS has the ability to keep track of the availability of blocks at different
219 rotational positions, so that it could lay out the data to be picked up with
220 minimum rotational latency. This parameter specifies the default number of
221 rotational positions to distinguish.
223 Nowadays this value should be set to 1 (which essentially disables the
224 rotational position table) because modern drives with read-ahead and
225 write-behind do better without the rotational position table.
226 .It Fl o Ar optimization\ preference
227 .Pq ``space'' or ``time''
228 The file system can either be instructed to try to minimize the time spent
229 allocating blocks, or to try to minimize the space fragmentation on the disk.
230 If the value of minfree (see above) is less than 8%,
231 the default is to optimize for space;
232 if the value of minfree is greater than or equal to 8%,
233 the default is to optimize for time.
236 for more details on how to set this option.
238 The size of the file system in sectors. This value defaults to the size of the
239 raw partition specified in
243 will use the entire partition for the file system).
245 Specify that the disk does not contain any partitions, and that
247 should build a file system on the whole disk.
248 This option is useful for synthetic disks such as
252 The following options override the standard sizes for the disk geometry.
253 Their default values are taken from the disk label.
254 Changing these defaults is useful only when using
256 to build a file system whose raw image will eventually be used on a
257 different type of disk than the one on which it is initially created
258 (for example on a write-once disk).
259 Note that changing any of these values from their defaults will make
262 to find the alternate superblocks if the standard superblock is lost.
263 .Bl -tag -width indent
264 .It Fl S Ar sector-size
265 The size of a sector in bytes (almost never anything but 512).
266 .It Fl k Ar sector \&0 skew , per track
267 Used to describe perturbations in the media format to compensate for
269 Track skew is the offset of sector 0 on track N relative to sector 0
270 on track N-1 on the same cylinder.
271 This option is of historical importance only; modern controllers are always fast
272 enough to handle operations back-to-back.
273 .It Fl l Ar hardware sector interleave
274 Used to describe perturbations in the media format to compensate for
276 Interleave is physical sector interleave on each track,
277 specified as the denominator of the ratio:
278 .Dl sectors read/sectors passed over
279 Thus an interleave of 1/1 implies contiguous layout, while 1/2 implies
280 logical sector 0 is separated by one sector from logical sector 1.
281 This option is of historical importance only; the physical sector layout of
282 modern disks is not visible from outside.
283 .It Fl p Ar spare sectors per track
284 Spare sectors (bad sector replacements) are physical sectors that occupy
285 space at the end of each track.
286 They are not counted as part of the sectors/track
288 since they are not available to the file system for data allocation.
289 This option is of historical importance only. Modern disks perform their own
290 bad sector allocation.
291 .It Fl r Ar revolutions/minute
292 The speed of the disk in revolutions per minute. This value is no longer of
293 interest, since all the parameters which depend on it are usually disabled.
295 .It Fl t Ar #tracks/cylinder
296 The number of tracks/cylinder available for data allocation by the file
299 If zero is specified, the value from the disklabel will be used.
300 .It Fl u Ar sectors/track
301 The number of sectors per track available for data allocation by the file
304 If zero is specified, the value from the disklabel will be used.
305 This does not include sectors reserved at the end of each track for bad
306 block replacement (see the
309 .It Fl x Ar spare sectors per cylinder
310 Spare sectors (bad sector replacements) are physical sectors that occupy
311 space at the end of the last track in the cylinder.
312 They are deducted from the sectors/track
314 of the last track of each cylinder since they are not available to the file
315 system for data allocation.
316 This option is of historical importance only. Modern disks perform their own
317 bad sector allocation.
322 command are as described for the
324 command, except for the
328 That option is as follows:
329 .Bl -tag -width indent
331 Options are specified with a
333 flag followed by a comma separated string of options.
336 man page for possible options and their meanings.
340 .Dl mount_mfs -s 131072 -o nosuid,nodev /dev/da0s1b /tmp
342 Mount a 64 MB large memory file system on /tmp, with
344 options nosuid and nodev.
348 assumes that the file system that carries the
349 kernel has blocks of 8 kilobytes and fragments of 1 kilobyte.
351 not be able to boot from a file system that uses another size.
369 .%T A Fast File System for UNIX ,
370 .%J ACM Transactions on Computer Systems 2
374 .%O (reprinted in the BSD System Manager's Manual)