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1.1 root 1: .\" Copyright (c) 1983, 1987 The Regents of the University of California.
2: .\" All rights reserved.
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18: .\" @(#)newfs.8 6.9 (Berkeley) 6/24/90
19: .\"
20: .TH NEWFS 8 "June 24, 1990"
21: .UC 5
22: .SH NAME
23: newfs, mfs \- construct a new file system
24: .SH SYNOPSIS
25: .B newfs
26: [
27: .B \-N
28: ] [
29: .B newfs-options
30: ]
31: .B special
32: .br
33: .B mfs
34: [
35: .B \-F
36: mount_flags
37: ] [
38: .B newfs-options
39: ]
40: .B special node
41: .SH DESCRIPTION
42: .I Newfs
43: replaces the more obtuse
44: .IR mkfs (8)
45: program.
46: Before running
47: .I newfs
48: or
49: .IR mfs ,
50: the disk must be labeled using
51: .IR disklabel (8).
52: .I Newfs
53: builds a file system on the specified special device
54: basing its defaults on the information in the disk label.
55: Typically the defaults are reasonable, however
56: .I newfs
57: has numerous options to allow the defaults to be selectively overridden.
58: The
59: .B \-N
60: option causes the file system parameters to be printed out
61: without really creating the file system.
62: .PP
63: .I Mfs
64: is used to build a file system in virtual memory and then mount it
65: on a specified node.
66: .I Mfs
67: exits and the contents of the file system are lost
68: when the file system is unmounted.
69: If
70: .I mfs
71: is sent a signal while running,
72: for example during system shutdown,
73: it will attempt to unmount its
74: corresponding file system.
75: The parameters to
76: .I mfs
77: are the same as those to
78: .IR newfs .
79: The special file is only used to read the disk label which provides
80: a set of configuration parameters for the memory based file system.
81: The special file is typically that of the primary swap area,
82: since that is where the file system will be backed up when
83: free memory gets low and the memory supporting
84: the file system has to be paged.
85: .PP
86: The following options define the general layout policies.
87: .TP 10
88: .B \-b block-size
89: The block size of the file system in bytes.
90: .TP 10
91: .B \-f frag-size
92: The fragment size of the file system in bytes.
93: .TP 10
94: .B \-m free space %
95: The percentage of space reserved from normal users; the minimum
96: free space threshold. The default value used is 10%.
97: See
98: .IR tunefs (8)
99: for more details on how to set this option.
100: .TP 10
101: .B \-o optimization preference (``space'' or ``time'')
102: The file system can either be instructed to try to minimize the time spent
103: allocating blocks, or to try to minimize the space fragmentation on the disk.
104: If the value of minfree (see above) is less than 10%,
105: the default is to optimize for space;
106: if the value of minfree greater than or equal to 10%,
107: the default is to optimize for time.
108: See
109: .IR tunefs (8)
110: for more details on how to set this option.
111: .TP 10
112: .B \-a maxcontig
113: This specifies the maximum number of contiguous blocks that will
114: be laid out before forcing a rotational delay (see \-d below).
115: The default value is one.
116: See
117: .IR tunefs (8)
118: for more details on how to set this option.
119: .TP 10
120: .B \-d rotdelay
121: This specifies the expected time (in milliseconds)
122: to service a transfer completion
123: interrupt and initiate a new transfer on the same disk.
124: The default is 4 milliseconds.
125: See
126: .IR tunefs (8)
127: for more details on how to set this option.
128: .TP 10
129: .B \-e maxbpg
130: This indicates 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.
134: See
135: .IR tunefs (8)
136: for more details on how to set this option.
137: .TP 10
138: .B \-i number of bytes per inode
139: This specifies the density of inodes in the file system.
140: The default is to create an inode for each 2048 bytes of data space.
141: If fewer inodes are desired, a larger number should be used;
142: to create more inodes a smaller number should be given.
143: .TP 10
144: .B \-c #cylinders/group
145: The number of cylinders per cylinder group in a file system.
146: The default value used is 16.
147: .TP 10
148: .B \-s size
149: The size of the file system in sectors.
150: .PP
151: The following options override the standard sizes for the disk geometry.
152: Their default values are taken from the disk label.
153: Changing these defaults is useful only when using
154: .I newfs
155: to build a file system whose raw image will eventually be used
156: on a different type of disk than the one on which it is initially
157: created (for example on a write-once disk).
158: Note that changing any of these values from their
159: defaults will make it impossible for
160: .I fsck
161: to find the alternate superblocks if the standard super block is lost.
162: .TP 10
163: .B \-r revolutions/minute
164: The speed of the disk in revolutions per minute.
165: .TP 10
166: .B \-S sector-size
167: The size of a sector in bytes (almost never anything but 512).
168: .TP 10
169: .B \-u sectors/track
170: The number of sectors/track available for data
171: allocation by the file system.
172: This does not include sectors reserved at the end of each track for
173: bad block replacement (see \fB\-p\fP below).
174: .TP 10
175: .B \-t #tracks/cylinder
176: The number of tracks/cylinder available for data
177: allocation by the file system.
178: .TP 10
179: .B \-p spare sectors per track
180: Spare sectors (bad sector replacements) are physical sectors
181: that occupy space at the end of each track.
182: They are not counted as part of the sectors/track (\fB\-u\fP)
183: since they are not available to the file system for data allocation.
184: .TP 10
185: .B \-x spare sectors per cylinder
186: Spare sectors (bad sector replacements) are physical sectors
187: that occupy space at the end of the last track in the cylinder.
188: They are deducted from the sectors/track (\fB\-u\fP)
189: of the last track of each cylinder
190: since they are not available to the file system for data allocation.
191: .TP 10
192: .B \-l hardware sector interleave
193: Used to describe perturbations in the media format to
194: compensate for a slow controller.
195: Interleave is physical sector interleave on each track,
196: specified as the denominator of the ratio:
197: .nf
198: sectors read / sectors passed over
199: .fi
200: Thus an interleave of 1/1 implies contiguous layout, while 1/2
201: implies logical sector 0 is separated by one sector from logical
202: sector 1.
203: .TP 10
204: .B \-k sector 0 skew, per track
205: Used to describe perturbations in the media format to
206: compensate for a slow controller.
207: Track skew is the offset of sector 0 on track N
208: relative to sector 0 on track N-1 on the same cylinder.
209: .PP
210: The following option applies only to
211: .IR mfs .
212: .TP 10
213: .B \-F mount flags
214: Used to pass in a decimal numeric value to be passed
215: as mount flags when running as a memory based file system.
216: This option is primarily intended for use when
217: .I mfs
218: is started by the
219: .IR mount (8)
220: command.
221: .SH "SEE ALSO"
222: disktab(5),
223: fs(5),
224: disklabel(8),
225: diskpart(8),
226: fsck(8),
227: format(8),
228: tunefs(8)
229: .PP
230: M. McKusick, W. Joy, S. Leffler, R. Fabry,
231: ``A Fast File System for UNIX'',
232: \fIACM Transactions on Computer Systems 2\fP, 3.
233: pp 181-197, August 1984.
234: (reprinted in the System Manager's Manual, SMM:14)
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