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28 .\" @(#)newfs.8 8.6 (Berkeley) 5/3/95
36 .Nd construct a new UFS1/UFS2 file system
41 .Op Fl O Ar filesystem-type
42 .Op Fl S Ar sector-size
45 .Op Fl b Ar block-size
46 .Op Fl c Ar blocks-per-cylinder-group
47 .Op Fl d Ar max-extent-size
50 .Op Fl g Ar avgfilesize
53 .Op Fl k Ar held-for-metadata-blocks
54 .Op Fl m Ar free-space
55 .Op Fl o Ar optimization
63 utility is used to initialize and clear file systems before first use.
66 utility builds a file system on the specified special file.
67 (We often refer to the
71 although the special file need not be a physical disk.
72 In fact, it need not even be special.)
73 Typically the defaults are reasonable, however
75 has numerous options to allow the defaults to be selectively overridden.
77 The following options define the general layout policies:
78 .Bl -tag -width indent
80 Erase the content of the disk before making the filesystem.
81 The reserved area in front of the superblock (for bootcode) will not be erased.
82 Erasing is only relevant to flash-memory or thinly provisioned devices.
83 Erasing may take a long time.
84 If the device does not support BIO_DELETE, the command will fail.
86 Enable journaling on the new file system via gjournal.
91 Add a volume label to the new file system.
92 Legal characters are alphanumerics, dashes, and underscores.
94 Cause the file system parameters to be printed out
95 without really creating the file system.
96 .It Fl O Ar filesystem-type
97 Use 1 to specify that a UFS1 format file system be built;
98 use 2 to specify that a UFS2 format file system be built.
99 The default format is UFS2.
101 For backward compatibility.
103 Enable soft updates on the new file system.
104 .It Fl a Ar maxcontig
105 Specify the maximum number of contiguous blocks that will be
106 laid out before forcing a rotational delay.
107 The default value is 16.
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.
113 It must be a power of 2.
115 default size is 32768 bytes, and the smallest allowable size is 4096 bytes.
116 The optimal block:fragment ratio is 8:1.
117 Other ratios are possible, but are not recommended,
118 and may produce poor results.
119 .It Fl c Ar blocks-per-cylinder-group
120 The number of blocks per cylinder group in a file system.
121 The default is to compute the maximum allowed by the other parameters.
123 dependent on a number of other parameters, in particular the block size
124 and the number of bytes per inode.
125 .It Fl d Ar max-extent-size
126 The file system may choose to store large files using extents.
127 This parameter specifies the largest extent size that may be used.
128 The default value is the file system blocksize.
129 It is presently limited to a maximum value of 16 times the
130 file system blocksize and a minimum value of the file system blocksize.
132 Indicate the maximum number of blocks any single file can
133 allocate out of a cylinder group before it is forced to begin
134 allocating blocks from another cylinder group.
135 The default is about one quarter of the total blocks in a cylinder group.
138 for more details on how to set this option.
139 .It Fl f Ar frag-size
140 The fragment size of the file system in bytes.
141 It must be a power of two
142 ranging in value between
146 The default is 4096 bytes.
147 .It Fl g Ar avgfilesize
148 The expected average file size for the file system.
150 The expected average number of files per directory on the file system.
152 Specify the density of inodes in the file system.
153 The default is to create an inode for every
156 If fewer inodes are desired, a larger number should be used;
157 to create more inodes a smaller number should be given.
158 One inode is required for each distinct file, so this value effectively
159 specifies the average file size on the file system.
161 Enable soft updates journaling on the new file system.
162 This flag is implemented by running the
164 utility found in the user's
166 .It Fl k Ar held-for-metadata-blocks
167 Set the amount of space to be held for metadata blocks in each cylinder group.
168 When set, the file system preference routines will try to save
169 the specified amount of space immediately following the inode blocks
170 in each cylinder group for use by metadata blocks.
171 Clustering the metadata blocks speeds up random file access
172 and decreases the running time of
176 sets it to half of the space reserved to minfree.
178 Enable multilabel MAC on the new file system.
179 .It Fl m Ar free-space
180 The percentage of space reserved from normal users; the minimum free
182 The default value used is
190 for more details on how to set this option.
194 directory on the new file system.
195 The resulting file system will not support snapshot generation, so
197 in live mode and background
199 will not function properly.
204 will work on the file system.
205 This option is intended primarily for memory or vnode-backed file systems that
211 .It Fl o Ar optimization
215 The file system can either be instructed to try to minimize the time spent
216 allocating blocks, or to try to minimize the space fragmentation on the disk.
217 If the value of minfree (see above) is less than 8%,
218 the default is to optimize for
220 if the value of minfree is greater than or equal to 8%,
221 the default is to optimize for
225 for more details on how to set this option.
226 .It Fl p Ar partition
227 The partition name (a..h) you want to use in case the underlying image
228 is a file, so you do not have access to individual partitions through the
230 Can also be used with a device, e.g.,
238 The size, in sectors, of reserved space
239 at the end of the partition specified in
241 This space will not be occupied by the file system;
242 it can be used by other consumers such as
246 The size of the file system in sectors.
247 This value defaults to the size of the
248 raw partition specified in
252 space at its end (see
256 of 0 can also be used to choose the default value.
259 value cannot be larger than the default one,
260 which means that the file system cannot extend into the reserved space.
262 Turn on the TRIM enable flag.
263 If enabled, and if the underlying device supports the BIO_DELETE
264 command, the file system will send a delete request to the underlying
265 device for each freed block.
266 The trim enable flag is typically set for flash-memory devices to
267 reduce write amplification which reduces wear on write-limited
268 flash-memory and often improves long-term performance.
269 Thinly provisioned storage also benefits by returning unused blocks to
273 The following options override the standard sizes for the disk geometry.
274 Their default values are taken from the disk label.
275 Changing these defaults is useful only when using
277 to build a file system whose raw image will eventually be used on a
278 different type of disk than the one on which it is initially created
279 (for example on a write-once disk).
280 Note that changing any of these values from their defaults will make
283 to find the alternate superblocks if the standard superblock is lost.
284 .Bl -tag -width indent
285 .It Fl S Ar sector-size
286 The size of a sector in bytes (almost never anything but 512).
289 .Dl newfs /dev/ada3s1a
291 Creates a new ufs file system on
295 utility will use a block size of 32768 bytes, a fragment size of 4096 bytes
296 and the largest possible number of blocks per cylinders group.
297 These values tend to produce better performance for most applications
298 than the historical defaults
299 (8192 byte block size and 1024 byte fragment size).
300 This large fragment size may lead to much wasted space
301 on file systems that contain many small files.
323 .%T A Fast File System for UNIX
324 .%J ACM Transactions on Computer Systems 2
328 .%O (reprinted in the BSD System Manager's Manual)