1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
|
.\" Copyright (c) 1980, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 4. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)swapon.8 8.1 (Berkeley) 6/5/93
.\" $FreeBSD$
.\"
.Dd December 28, 2002
.Dt SWAPON 8
.Os
.Sh NAME
.Nm swapon , swapoff , swapctl
.Nd "specify devices for paging and swapping"
.Sh SYNOPSIS
.Nm swapon Ar
.Nm swapon Fl a
.Nm swapoff Ar
.Nm swapoff Fl a
.Nm swapctl
.Op Fl AhklsU
.Oo
.Fl a Ar
|
.Fl d Ar
.Oc
.Sh DESCRIPTION
The
.Nm swapon , swapoff
and
.Nm swapctl
utilities are used to control swap devices in the system.
At boot time all swap entries in
.Pa /etc/fstab
are added automatically when the system goes multi-user.
Swap devices use a fixed interleave; the maximum number of devices
is specified by the kernel configuration option
.Dv NSWAPDEV ,
which is typically set to 4.
There is no priority mechanism.
.Pp
The
.Nm swapon
utility adds the specified swap devices to the system.
If the
.Fl a
option is used, all swap devices in
.Pa /etc/fstab
will be added, unless their
.Dq noauto
option is also set.
.Pp
The
.Nm swapoff
utility removes the specified swap devices from the system.
If the
.Fl a
option is used, all swap devices in
.Pa /etc/fstab
will be removed, unless their
.Dq noauto
option is also set.
Note that
.Nm swapoff
will fail and refuse to remove a swap device if there is insufficient
VM (memory + remaining swap devices) to run the system.
The
.Nm swapoff
utility
must move swapped pages out of the device being removed which could
lead to high system loads for a period of time, depending on how
much data has been swapped out to that device.
.Pp
The
.Nm swapctl
utility exists primarily for those familiar with other
.Bx Ns s
and may be
used to add, remove, or list swap devices.
Note that the
.Fl a
option is used differently in
.Nm swapctl
and indicates that a specific list of devices should be added.
The
.Fl d
option indicates that a specific list should be removed.
The
.Fl A
and
.Fl U
options to
.Nm swapctl
operate on all swap entries in
.Pa /etc/fstab
which do not have their
.Dq noauto
option set.
.Pp
Swap information can be generated using the
.Xr swapinfo 8
utility,
.Nm pstat
.Fl s ,
or
.Nm swapctl
.Fl l .
The
.Nm swapctl
utility has the following options for listing swap:
.Bl -tag -width indent
.It Fl h
Output values in megabytes.
.It Fl k
Output values in kilobytes.
.It Fl l
List the devices making up system swap.
.It Fl s
Print a summary line for system swap.
.Pp
The
.Ev BLOCKSIZE
environment variable is used if not specifically
overridden.
512 byte blocks are used by default.
.El
.Sh FILES
.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact
.It Pa /dev/{ad,da}?s?b
standard paging devices
.It Pa /dev/md?
memory disk devices
.It Pa /etc/fstab
.Tn ASCII
file system description table
.El
.Sh DIAGNOSTICS
These utilities may fail for the reasons described in
.Xr swapon 2 .
.Sh SEE ALSO
.Xr swapon 2 ,
.Xr fstab 5 ,
.Xr init 8 ,
.Xr mdconfig 8 ,
.Xr pstat 8 ,
.Xr rc 8
.Sh HISTORY
The
.Nm swapon
utility appeared in
.Bx 4.0 .
The
.Nm swapoff
and
.Nm swapctl
utilities appeared in
.Fx 5.1 .
|
