NEWFS(8) BSD System Manager's Manual NEWFS(8)
newfs, mount_mfs - construct a new file system
newfs [-NOq] [-a maxcontig] [-b block-size] [-c cylinders] [-d rotdelay] [-e maxbpg] [-f frag-size] [-g avgfilesize] [-h avgfpdir] [-i bytes] [-k skew] [-l interleave] [-m free-space] [-n nrpos] [-o optimization] [-p sectors] [-r revolutions] [-S sector-size] [-s size] [-t fstype] [-u sectors] [-x sectors] [-z tracks] special mount_mfs [-a maxcontig] [-b block-size] [-c cylinders] [-d rotdelay] [-e maxbpg] [-f frag-size] [-i bytes] [-m free space] [-o options] [-P file] [-s size] special node
Before running newfs or mount_mfs, the disk must be labeled using disklabel(8). newfs builds a file system on the specified special device, basing its defaults on the information in the disk label. Typically the defaults are reasonable, although newfs has numerous options to allow the defaults to be selectively overridden. mount_mfs is used to build a file system in virtual memory and then mount it on a specified node. mount_mfs exits and the contents of the file sys- tem are lost when the file system is unmounted. If mount_mfs is sent a signal while running, for example during system shutdown, it will attempt to unmount its corresponding file system. The parameters to mount_mfs are the same as those to newfs. The special file is only used to read the disk label which provides a set of configuration parameters for the memory based file system. The special file is typically that of the pri- mary swap area, since that is where the file system will be backed up when free memory gets low and the memory supporting the file system has to be paged. If the keyword "swap" is used instead of a special file name, default configuration parameters will be used. (This option is use- ful when trying to use mount_mfs on a machine without any disks.) Both newfs and mount_mfs now have the functionality of fsirand(8) built in, so it is not necessary to run fsirand(8) manually unless you wish to re-randomize the file system (or list the inode generation numbers). The following options define the general layout policies: -a maxcontig This specifies the maximum number of contiguous blocks that will be laid out before forcing a rotational delay (see the -d option). The default value depends on the block size (4 for 16KB blocks, 8 for 8KB blocks, and 16 for 4KB blocks). See tunefs(8) for more details on how to set this option. -b block-size The block size of the file system, in bytes. The default is 16KB. -c cylinders The number of cylinders per cylinder group in a file system. The default is to use as many as fit with the other parame- ters given. -d rotdelay This specifies the expected time (in milliseconds) to service a transfer completion interrupt and initiate a new transfer on the same disk. The default is 0 milliseconds. See tunefs(8) for more details on how to set this option. -e maxbpg This indicates the maximum number of blocks any single file can allocate out of a cylinder group before it is forced to begin allocating blocks from another cylinder group. The de- fault is about one quarter of the total blocks in a cylinder group. See tunefs(8) for more details on how to set this op- tion. -f frag-size The fragment size of the file system in bytes. The default is 2048. -g avgfilesize The expected average file size for the file system in bytes. -h avgfpdir The expected average number of files per directory on the file system. -i bytes This specifies the density of inodes in the file system. The default is to create an inode for each 8192 bytes of data space. If fewer inodes are desired, a larger number should be used; to create more inodes a smaller number should be given. -m free-space The percentage of space reserved from normal users; the minimum free space threshold. The default value used is 5%. See tunefs(8) for more details on how to set this option. -N Causes the file system parameters to be printed out without really creating the file system. -n nrpos The number of distinct rotational positions. The default is 1. -O Creates a 4.3BSD format file system. This option is primarily used to build root file systems that can be understood by older boot ROMs. -o optimization space or time. The file system can either be instructed to try to minimize the time spent allocating blocks, or to try to minimize the space fragmentation on the disk. Unless an optimization has been specified, if the value of minfree (see above) is less than 5%, the default is to optimize for space; if the value of minfree is greater than or equal to 5%, the default is to optimize for time. See tunefs(8) for more de- tails on how to set this option. -q Operate in quiet mode. With this option, newfs will not print extraneous information like superblock backups. -s size The size of the file system in sectors. The maximum size of a file system is 2,147,483,647 (2^31 - 1) sectors, which is slightly less than 1TB. The following options override the standard sizes for the disk geometry. Their default values are taken from the disk label. Changing these de- faults is useful only when using newfs to build a file system whose raw image will eventually be used on a different type of disk than the one on which it is initially created (for example on a write-once disk). Note that changing any of these values from their defaults will make it impos- sible for fsck(8) to find the alternate superblocks if the standard su- perblock is lost. -k skew Used to describe perturbations in the media format to compen- sate for a slow controller. Track skew is the offset of sec- tor 0 on track N relative to sector 0 on track N-1 on the same cylinder. -l interleave Used to describe perturbations in the media format to compen- sate for a slow controller. Interleave is physical sector in- terleave on each track, specified as the denominator of the ratio: sectors read/sectors passed over Thus an interleave of 1/1 implies contiguous layout, while 1/2 implies logical sector 0 is separated by one sector from logical sector 1. -p sectors Spare sectors (bad sector replacements) are physical sectors that occupy space at the end of each track. They are not counted as part of the sectors/track (-u) since they are not available to the file system for data allocation. -r revolutions The speed of the disk in revolutions per minute. -S sector-size The size of a sector in bytes (almost never anything but 512). -t fstype Set the file system type of which file system you wish to create. newfs will be smart enough to run the alternate newfs_XXX program instead. -u sectors The number of sectors per track available for data allocation by the file system. This does not include sectors reserved at the end of each track for bad block replacement (see the -p option). -x sectors Spare sectors (bad sector replacements) are physical sectors that occupy space at the end of the last track in the cylinder. They are deducted from the sectors/track (-u) of the last track of each cylinder since they are not available to the file system for data allocation. -z tracks The number of tracks/cylinder available for data allocation by the file system. The options to the mount_mfs command are as described for the newfs com- mand, except for the -o and -P options. These options are as follows: -o options Options are specified with a -o flag followed by a comma separat- ed string of options. See the mount(8) man page for possible op- tions and their meanings. -P file If file is a directory, populate the created mfs file system with the contents of the directory. If file is a block device, popu- late the created mfs file system with the contents of the FFS file system contained on the device. If the -P file option is not used, the owner and mode of the created mfs file system will be the same as the owner and mode of the mount point.
TMPDIR Directory in which to create temporary mount points for use by mount_mfs -P instead of /tmp.
disktab(5), fs(5), disklabel(8), dumpfs(8), fsck(8), fsirand(8), growfs(8), mount(8), tunefs(8) M. McKusick, W. Joy, S. Leffler, and R. Fabry, "A Fast File System for UNIX", ACM Transactions on Computer Systems 2, 3, pp 181-197, August 1984, (reprinted in the BSD System Manager's Manual).
The newfs command appeared in 4.2BSD. MirOS BSD #10-current March 27, 1994 3
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