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Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)newfs.8 8.6 (Berkeley) 5/3/95 33.\" $FreeBSD: src/sbin/newfs/newfs.8,v 1.26.2.15 2003/05/13 12:16:08 joerg Exp $ 34.\" $DragonFly: src/sbin/newfs/newfs.8,v 1.7 2007/05/20 19:29:21 dillon Exp $ 35.\" 36.Dd May 13, 2003 37.Dt NEWFS 8 38.Os 39.Sh NAME 40.Nm newfs , 41.Nm mount_mfs 42.Nd construct a new file system 43.Sh SYNOPSIS 44.Nm 45.Op Fl NCOU 46.Op Fl S Ar sector-size 47.Op Fl T Ar disktype 48.Op Fl a Ar maxcontig 49.Op Fl b Ar block-size 50.Op Fl c Ar cylinders 51.Op Fl d Ar rotdelay 52.Op Fl e Ar maxbpg 53.Op Fl f Ar frag-size 54.Op Fl g Ar avgfilesize 55.Op Fl h Ar avfpdir 56.Op Fl i Ar bytes 57.Op Fl k Ar skew 58.Op Fl l Ar interleave 59.Op Fl m Ar free space 60.Op Fl n Ar rotational positions 61.Op Fl o Ar optimization 62.Op Fl p Ar sectors 63.Op Fl r Ar revolutions 64.Op Fl s Ar size 65.Op Fl t Ar tracks 66.Op Fl u Ar sectors 67.Op Fl v 68.Op Fl x Ar sectors 69.Ar special 70.Nm mount_mfs 71.Op Fl NU 72.Op Fl F Ar file 73.Op Fl T Ar disktype 74.Op Fl a Ar maxcontig 75.Op Fl b Ar block-size 76.Op Fl c Ar cylinders 77.Op Fl d Ar rotdelay 78.Op Fl e Ar maxbpg 79.Op Fl f Ar frag-size 80.Op Fl i Ar bytes 81.Op Fl m Ar free space 82.Op Fl n Ar rotational positions 83.Op Fl o Ar options 84.Op Fl s Ar size 85.Op Fl v 86.Ar special node 87.Sh DESCRIPTION 88.Nm Newfs 89is used to initialize and clear filesystems before first use. 90Before running 91.Nm 92or 93.Nm mount_mfs , 94the disk must be labeled using 95.Xr disklabel 8 . 96.Nm Newfs 97builds a file system on the specified special file. 98(We often refer to the 99.Dq special file 100as the 101.Dq disk , 102although the special file need not be a physical disk. 103In fact, it need not even be special.) 104Typically the defaults are reasonable, however 105.Nm 106has numerous options to allow the defaults to be selectively overridden. 107.Pp 108.Nm Mount_mfs 109is used to build a file system in virtual memory and then mount it 110on a specified node. 111.Nm Mount_mfs 112exits and the contents of the file system are lost 113when the file system is unmounted. 114If 115.Nm mount_mfs 116is sent a signal while running, 117for example during system shutdown, 118it will attempt to unmount its 119corresponding file system. 120The parameters to 121.Nm mount_mfs 122are the same as those to 123.Nm . 124If the 125.Fl T 126flag is specified (see below), the special file is unused. 127Otherwise, it is only used to read the disk label which provides 128a set of configuration parameters for the memory based file system. 129The special file is typically that of the primary swap area, 130since that is where the file system will be backed up when 131free memory gets low and the memory supporting 132the file system has to be paged. 133.Pp 134.Nm mount_mfs 135creates the raw character device 136.Pa /dev/mfs<PID> 137to represent the backing store while the mount is active. This device may 138be read but not written and allows swap-based MFS filesystems to be dumped 139if desired. 140.Pp 141The following options define the general layout policies: 142.Bl -tag -width indent 143.It Fl T Ar disktype 144For backward compatibility and for 145.Nm mount_mfs . 146.It Fl F Ar file 147.Nm Mount_mfs 148will use this file for the image of the filesystem. When 149.Nm mount_mfs 150exits, this file will be left behind. 151.It Fl C 152Tell 153.Nm Mount_mfs 154to copy the underlying filesystem into the MFS mount being created 155over it. 156.It Fl N 157Cause the file system parameters to be printed out 158without really creating the file system. 159.It Fl O 160Create a 161.Bx 4.3 162format filesystem. 163This options is primarily used to build root filesystems 164that can be understood by older boot ROMs. 165.It Fl T 166Use information for the specified disk from 167.Pa /etc/disktab 168instead of trying to get geometry information from the 169storage device. 170.It Fl U 171Enables soft updates on the new filesystem. 172.It Fl a Ar maxcontig 173Specify the maximum number of contiguous blocks that will be 174laid out before forcing a rotational delay (see the 175.Fl d 176option). 177The default value is 1. 178See 179.Xr tunefs 8 180for more details on how to set this option. 181.It Fl b Ar block-size 182The block size of the file system, in bytes. It must be a power of 2. The 183default size is 16384 bytes, and the smallest allowable size is 4096 bytes. 184The optimal block:fragment ratio is 8:1. 185Other ratios are possible, but are not recommended, 186and may produce unpredictable results. 187.It Fl c Ar #cylinders/group 188The number of cylinders per cylinder group in a file system. The default 189is to compute the maximum allowed by the other parameters. This value is 190dependent on a number of other parameters, in particular the block size 191and the number of bytes per inode. 192.It Fl d Ar rotdelay 193This parameter once specified the minimum time in milliseconds required to 194initiate another disk transfer on the same cylinder. It was used in determining 195the rotationally optimal layout for disk blocks within a file. Modern disks 196with read/write-behind achieve higher performance with this feature disabled, so 197this value should be left at the default value of 0 milliseconds. See 198.Xr tunefs 8 199for more details on how to set this option. 200.It Fl e Ar maxbpg 201Indicate the maximum number of blocks any single file can 202allocate out of a cylinder group before it is forced to begin 203allocating blocks from another cylinder group. 204The default is about one quarter of the total blocks in a cylinder group. 205See 206.Xr tunefs 8 207for more details on how to set this option. 208.It Fl f Ar frag-size 209The fragment size of the file system in bytes. It must be a power of two 210ranging in value between 211.Ar blocksize Ns /8 212and 213.Ar blocksize . 214The default is 2048 bytes. 215.It Fl g Ar avgfilesize 216The expected average file size for the file system. 217.It Fl h Ar avgfpdir 218The expected average number of files per directory on the file system. 219.It Fl i Ar number of bytes per inode 220Specify the density of inodes in the file system. 221The default is to create an inode for every 222.Pq 4 * Ar frag-size 223bytes of data space. 224If fewer inodes are desired, a larger number should be used; 225to create more inodes a smaller number should be given. 226One inode is required for each distinct file, so this value effectively 227specifies the average file size on the file system. 228.It Fl m Ar free space \&% 229The percentage of space reserved from normal users; the minimum free 230space threshold. 231The default value used is 232defined by 233.Dv MINFREE 234from 235.In ufs/ffs/fs.h , 236currently 8%. 237See 238.Xr tunefs 8 239for more details on how to set this option. 240.It Fl n Ar number of distinguished rotational positions 241UFS has the ability to keep track of the availability of blocks at different 242rotational positions, so that it could lay out the data to be picked up with 243minimum rotational latency. This parameter specifies the default number of 244rotational positions to distinguish. 245.Pp 246Nowadays this value should be set to 1 (which essentially disables the 247rotational position table) because modern drives with read-ahead and 248write-behind do better without the rotational position table. 249.It Fl o Ar optimization\ preference 250.Pq Ar space No or Ar time . 251The file system can either be instructed to try to minimize the time spent 252allocating blocks, or to try to minimize the space fragmentation on the disk. 253If the value of minfree (see above) is less than 8%, 254the default is to optimize for 255.Ar space ; 256if the value of minfree is greater than or equal to 8%, 257the default is to optimize for 258.Ar time . 259See 260.Xr tunefs 8 261for more details on how to set this option. 262.It Fl s Ar size 263The size of the file system in sectors. This value defaults to the size of the 264raw partition specified in 265.Ar special 266(in other words, 267.Nm 268will use the entire partition for the file system). 269.It Fl v 270Specify that the disk does not contain any partitions, and that 271.Nm 272should build a file system on the whole disk. 273This option is useful for synthetic disks such as 274.Nm vinum . 275It may also be used to allow 276.Nm 277to operate on regular files. 278When operating on a regular file, 279.Nm 280will synthesize a reasonable geometry for the filesystem. 281.El 282.Pp 283The following options override the standard sizes for the disk geometry. 284Their default values are taken from the disk label. 285Changing these defaults is useful only when using 286.Nm 287to build a file system whose raw image will eventually be used on a 288different type of disk than the one on which it is initially created 289(for example on a write-once disk). 290Note that changing any of these values from their defaults will make 291it impossible for 292.Xr fsck 8 293to find the alternate superblocks if the standard superblock is lost. 294.Bl -tag -width indent 295.It Fl S Ar sector-size 296The size of a sector in bytes (almost never anything but 512). 297.It Fl k Ar sector \&0 skew , per track 298Used to describe perturbations in the media format to compensate for 299a slow controller. 300Track skew is the offset of sector 0 on track N relative to sector 0 301on track N-1 on the same cylinder. 302This option is of historical importance only; modern controllers are always fast 303enough to handle operations back-to-back. 304.It Fl l Ar hardware sector interleave 305Used to describe perturbations in the media format to compensate for 306a slow controller. 307Interleave is physical sector interleave on each track, 308specified as the denominator of the ratio: 309.Dl sectors read/sectors passed over 310Thus an interleave of 1/1 implies contiguous layout, while 1/2 implies 311logical sector 0 is separated by one sector from logical sector 1. 312This option is of historical importance only; the physical sector layout of 313modern disks is not visible from outside. 314.It Fl p Ar spare sectors per track 315Spare sectors (bad sector replacements) are physical sectors that occupy 316space at the end of each track. 317They are not counted as part of the sectors/track 318.Pq Fl u 319since they are not available to the file system for data allocation. 320This option is of historical importance only. Modern disks perform their own 321bad sector allocation. 322.It Fl r Ar revolutions/minute 323The speed of the disk in revolutions per minute. This value is no longer of 324interest, since all the parameters which depend on it are usually disabled. 325.It Fl t Ar #tracks/cylinder 326The number of tracks/cylinder available for data allocation by the file 327system. 328The default is 1. 329If zero is specified, the value from the device geometry will be used. 330.It Fl u Ar sectors/track 331The number of sectors per track available for data allocation by the file 332system. 333The default is 4096. 334If zero is specified, the value from the device geometry will be used. 335This does not include sectors reserved at the end of each track for bad 336block replacement (see the 337.Fl p 338option). 339.It Fl x Ar spare sectors per cylinder 340Spare sectors (bad sector replacements) are physical sectors that occupy 341space at the end of the last track in the cylinder. 342They are deducted from the sectors/track 343.Pq Fl u 344of the last track of each cylinder since they are not available to the file 345system for data allocation. 346This option is of historical importance only. Modern disks perform their own 347bad sector allocation. 348.El 349.Pp 350The options to the 351.Nm mount_mfs 352command are as described for the 353.Nm 354command, except for the 355.Fl o 356option. 357.Pp 358That option is as follows: 359.Bl -tag -width indent 360.It Fl o 361Options are specified with a 362.Fl o 363flag followed by a comma separated string of options. 364See the 365.Xr mount 8 366man page for possible options and their meanings. 367.El 368.Sh EXAMPLES 369.Dl newfs /dev/ad3s1a 370.Pp 371Creates a new ufs file system on 372.Pa ad3s1a . 373.Nm 374will use a block size of 16384 bytes, a fragment size of 2048 bytes 375and the largest possible number of cylinders per group. 376These values tend to produce better performance for most applications 377than the historical defaults 378(8192 byte block size and 1024 byte fragment size). 379This large fragment size 380may lead to large amounts of wasted space 381on filesystems that contain a large number of small files. 382.Pp 383.Dl mount_mfs -s 131072 -o nosuid,nodev,nosymfollow /dev/da0s1b /tmp 384.Pp 385Mount a 64 MB large memory file system on 386.Pa /tmp , 387with 388.Xr mount 8 389options 390.Ar nosuid , 391.Ar nodev , 392and 393.Ar nosymfollow . 394.Sh SEE ALSO 395.Xr fdformat 1 , 396.Xr disktab 5 , 397.Xr fs 5 , 398.Xr camcontrol 8 , 399.Xr disklabel 8 , 400.Xr dumpfs 8 , 401.Xr fsck 8 , 402.Xr mount 8 , 403.Xr tunefs 8 , 404.Xr vinum 8 405.Rs 406.%A M. McKusick 407.%A W. Joy 408.%A S. Leffler 409.%A R. Fabry 410.%T A Fast File System for UNIX 411.%J ACM Transactions on Computer Systems 2 412.%V 3 413.%P pp 181-197 414.%D August 1984 415.%O (reprinted in the BSD System Manager's Manual) 416.Re 417.Sh HISTORY 418The 419.Nm 420command appeared in 421.Bx 4.2 . 422