NEWFS(8) NetBSD System Manager's Manual NEWFS(8)
NAME
newfs, mount_mfs - construct a new file system
SYNOPSIS
newfs [-NO] [-S sector-size] [-T disktype] [-a maxcontig] [-b block-size] [-c cylinders] [-d rotdelay] [-e maxbpg] [-f frag-size] [-i bytes] [-k skew] [-l interleave] [-m free space] [-n rotational positions] [-o optimization] [-p sectors] [-r revolutions] [-s size] [-t tracks] [-u sectors] [-x sectors] special mount_mfs [-N] [-T disktype] [-a maxcontig] [-b block-size] [-c cylinders] [-d rotdelay] [-e maxbpg] [-f frag-size] [-i bytes] [-m free space] [-n rotational positions] [-o options] [-s size] special node
DESCRIPTION
newfs replaces the more obtuse mkfs program. 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, however newfs has numerous options to allow the defaults to be selective- ly 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 system are lost when the file system is unmounted. If mount_mfs is sent a signal while running, for example during system shutdown, it will at- tempt to unmount its corresponding file system. The parameters to mount_mfs are the same as those to newfs. If the -T flag is specified (see below), the special file is unused. Otherwise, it 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 primary 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 useful when trying to use mount_mfs on a machine without any disks.) The following options define the general layout policies. -N Causes the file system parameters to be printed out without really creating the file system. -O Creates a 4.3BSD format filesystem. This options is primari- ly used to build root filesystems that can be understood by older boot ROMs. -T Uses information for the specified disk from /etc/disktab in- stead of trying to get the information from a disklabel. -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 is 8. See tunefs(8) for more details on how to set this option. -b block-size The block size of the file system, in bytes. -c #cylinders/group The number of cylinders per cylinder group in a file system. The default value is 16. -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. -i number of bytes per inode This specifies the density of inodes in the file system. The default is to create an inode for each 4096 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 mini- mum free space threshold. The default value used is 5%. See tunefs(8) for more details on how to set this option. -n rotational positions Determines how many rotational time slots there are in one revolution of the disk. -o optimization preference (``space'' or ``time'') The file system can either be in- structed to try to minimize the time spent allocating blocks, or to try to minimize the space fragmentation on the disk. If the value of minfree (see above) is less than 5%, the de- fault 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 details on how to set this op- tion. -s size The size of the file system in sectors. 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_ffs to find the alternative superblocks if the standard superblock is lost. -S sector-size The size of a sector in bytes (almost never anything but 512). -k sector 0 skew, per track 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 hardware sector interleave Used to describe perturbations in the media format to compen- sate for a slow controller. Interleave is physical sector interleave 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 spare sectors per track 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/minute The speed of the disk in revolutions per minute. -t #tracks/cylinder The number of tracks/cylinder available for data allocation by the file system. -u sectors/track 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 spare sectors per cylinder Spare sectors (bad sector replacements) are physical sectors that occupy space at the end of the last track in the cylin- der. 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. The options to the mount_mfs command are as described for the newfs com- mand, except for the -o option. That option is as follows: -o 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.
SEE ALSO
disktab(5), fs(5), dumpfs(8), disklabel(8), diskpart(8), fsck_ffs(8), format(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).
HISTORY
The newfs command appeared in 4.2BSD. 4.2 Berkeley Distribution May 3, 1995 3
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