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32 .\" @(#)newfs.8 8.6 (Berkeley) 5/3/95
40 .Nd construct a new file system
44 .Op Fl S Ar sector-size
47 .Op Fl b Ar block-size
52 .Op Fl g Ar avgfilesize
56 .Op Fl l Ar interleave
57 .Op Fl m Ar free space
58 .Op Fl n Ar rotational positions
59 .Op Fl o Ar optimization
61 .Op Fl r Ar revolutions
70 is used to initialize and clear filesystems before first use.
73 the disk must be labeled using
76 builds a file system on the specified special file.
77 (We often refer to the
81 although the special file need not be a physical disk.
82 In fact, it need not even be special.)
83 Typically the defaults are reasonable, however
85 has numerous options to allow the defaults to be selectively overridden.
87 The following options define the general layout policies:
88 .Bl -tag -width indent
90 For backward compatibility.
92 Cause the file system parameters to be printed out
93 without really creating the file system.
98 This options is primarily used to build root filesystems
99 that can be understood by older boot ROMs.
101 Enables soft updates on the new filesystem.
102 .It Fl a Ar maxcontig
103 Specify the maximum number of contiguous blocks that will be
104 laid out before forcing a rotational delay (see the
107 The default value is 1.
110 for more details on how to set this option.
111 .It Fl b Ar block-size
112 The block size of the file system, in bytes. It must be a power of 2. The
113 default size is 8192 bytes, and the smallest allowable size is 4096 bytes.
114 .It Fl c Ar #cylinders/group
115 The number of cylinders per cylinder group in a file system. The default value
116 is 22. The maximum value is dependent on a number of other parameters, in
117 particular the block size. The best way to find the maximum value for a
118 specific file system is to attempt to specify a value which is far too large:
120 will print out the maximum value.
122 This parameter once specified the minimum time in milliseconds required to
123 initiate another disk transfer on the same cylinder. It was used in determining
124 the rotationally optimal layout for disk blocks within a file. Modern disks
125 with read/write-behind achieve higher performance with this feature disabled, so
126 this value should be left at the default value of 0 milliseconds. See
128 for more details on how to set this option.
130 Indicate the maximum number of blocks any single file can
131 allocate out of a cylinder group before it is forced to begin
132 allocating blocks from another cylinder group.
133 The default is about one quarter of the total blocks in a cylinder group.
136 for more details on how to set this option.
137 .It Fl f Ar frag-size
138 The fragment size of the file system in bytes. It must be a power of two
139 ranging in value between
143 The default is 1024 bytes.
144 .It Fl g Ar avgfilesize
145 The expected average file size for the file system.
147 The expected average number of files per directory on the file system.
148 .It Fl i Ar number of bytes per inode
149 Specify the density of inodes in the file system.
150 The default is to create an inode for every
153 If fewer inodes are desired, a larger number should be used;
154 to create more inodes a smaller number should be given.
155 One inode is required for each distinct file, so this value effectively
156 specifies the average file size on the file system.
157 .It Fl m Ar free space \&%
158 The percentage of space reserved from normal users; the minimum free
160 The default value used is
164 .Aq Pa ufs/ffs/fs.h ,
168 for more details on how to set this option.
169 .It Fl n Ar number of distinguished rotational positions
170 UFS has the ability to keep track of the availability of blocks at different
171 rotational positions, so that it could lay out the data to be picked up with
172 minimum rotational latency. This parameter specifies the default number of
173 rotational positions to distinguish.
175 Nowadays this value should be set to 1 (which essentially disables the
176 rotational position table) because modern drives with read-ahead and
177 write-behind do better without the rotational position table.
178 .It Fl o Ar optimization\ preference
179 .Pq Ar space No or Ar time .
180 The file system can either be instructed to try to minimize the time spent
181 allocating blocks, or to try to minimize the space fragmentation on the disk.
182 If the value of minfree (see above) is less than 8%,
183 the default is to optimize for
185 if the value of minfree is greater than or equal to 8%,
186 the default is to optimize for
190 for more details on how to set this option.
192 The size of the file system in sectors. This value defaults to the size of the
193 raw partition specified in
197 will use the entire partition for the file system).
199 Specify that the disk does not contain any partitions, and that
201 should build a file system on the whole disk.
202 This option is useful for synthetic disks such as
206 The following options override the standard sizes for the disk geometry.
207 Their default values are taken from the disk label.
208 Changing these defaults is useful only when using
210 to build a file system whose raw image will eventually be used on a
211 different type of disk than the one on which it is initially created
212 (for example on a write-once disk).
213 Note that changing any of these values from their defaults will make
216 to find the alternate superblocks if the standard superblock is lost.
217 .Bl -tag -width indent
218 .It Fl S Ar sector-size
219 The size of a sector in bytes (almost never anything but 512).
220 .It Fl k Ar sector \&0 skew , per track
221 Used to describe perturbations in the media format to compensate for
223 Track skew is the offset of sector 0 on track N relative to sector 0
224 on track N-1 on the same cylinder.
225 This option is of historical importance only; modern controllers are always fast
226 enough to handle operations back-to-back.
227 .It Fl l Ar hardware sector interleave
228 Used to describe perturbations in the media format to compensate for
230 Interleave is physical sector interleave on each track,
231 specified as the denominator of the ratio:
232 .Dl sectors read/sectors passed over
233 Thus an interleave of 1/1 implies contiguous layout, while 1/2 implies
234 logical sector 0 is separated by one sector from logical sector 1.
235 This option is of historical importance only; the physical sector layout of
236 modern disks is not visible from outside.
237 .It Fl p Ar spare sectors per track
238 Spare sectors (bad sector replacements) are physical sectors that occupy
239 space at the end of each track.
240 They are not counted as part of the sectors/track
242 since they are not available to the file system for data allocation.
243 This option is of historical importance only. Modern disks perform their own
244 bad sector allocation.
245 .It Fl r Ar revolutions/minute
246 The speed of the disk in revolutions per minute. This value is no longer of
247 interest, since all the parameters which depend on it are usually disabled.
248 .It Fl t Ar #tracks/cylinder
249 The number of tracks/cylinder available for data allocation by the file
252 If zero is specified, the value from the disklabel will be used.
253 .It Fl u Ar sectors/track
254 The number of sectors per track available for data allocation by the file
257 If zero is specified, the value from the disklabel will be used.
258 This does not include sectors reserved at the end of each track for bad
259 block replacement (see the
262 .It Fl x Ar spare sectors per cylinder
263 Spare sectors (bad sector replacements) are physical sectors that occupy
264 space at the end of the last track in the cylinder.
265 They are deducted from the sectors/track
267 of the last track of each cylinder since they are not available to the file
268 system for data allocation.
269 This option is of historical importance only. Modern disks perform their own
270 bad sector allocation.
273 .Dl newfs -b 16384 -f 4096 -c 100 /dev/ad3s1a
275 Creates a new ufs file system on
278 will use a block size of 16384 bytes, a fragement size of 4096 bytes
279 and have 100 cylinders per cylinder group rather than the defaults.
280 These values are tend to produce better performance than the defaults
281 for file systems larger than about 5 gigabytes.
299 .%T A Fast File System for UNIX
300 .%J ACM Transactions on Computer Systems 2
304 .%O (reprinted in the BSD System Manager's Manual)