TRIM support
[dragonfly.git] / sbin / swapon / swapon.8
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32.\" @(#)swapon.8 8.1 (Berkeley) 6/5/93
33.\" $FreeBSD: src/sbin/swapon/swapon.8,v 1.15.2.2 2001/12/14 15:17:56 ru Exp $
f5ba7fbd 34.\" $DragonFly: src/sbin/swapon/swapon.8,v 1.4 2007/08/10 18:28:27 swildner Exp $
984263bc 35.\"
9f3543c6 36.Dd September 7, 2010
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37.Dt SWAPON 8
38.Os
39.Sh NAME
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40.Nm swapon , swapoff , swapctl
41.Nd "specify devices for paging and swapping"
984263bc 42.Sh SYNOPSIS
e0fb398b 43.Nm swapon Fl aeq | Ar
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44.Nm swapoff Fl aq | Ar
45.Nm swapctl
e0fb398b 46.Op Fl AeghklmsU
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47.Oo
48.Fl a Ar
49|
50.Fl d Ar
51.Oc
984263bc 52.Sh DESCRIPTION
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53The
54.Nm swapon , swapoff
55and
56.Nm swapctl
57utilities are used to control swap devices in the system.
58At boot time all swap entries in
59.Pa /etc/fstab
60are added automatically when the system goes multi-user.
61Swap devices use a fixed interleave; the maximum number of devices
62is specified by the kernel configuration option
63.Dv NSWAPDEV ,
64which is typically set to 4.
65There is no priority mechanism.
984263bc 66.Pp
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67The
68.Nm swapon
69utility adds the specified swap devices to the system.
70If the
71.Fl a
72option is used, all swap devices in
984263bc 73.Pa /etc/fstab
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74will be added, unless their
75.Dq noauto
76option is also set.
77If the
78.Fl q
79option is used informational messages will not be
80written to standard output when a swap device is added.
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81If the
82.Fl e
83option is used, the device will be trimmed if
84it supports trim and the trim_enabled sysctl is on.
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85.Pp
86The
87.Nm swapoff
88utility removes the specified swap devices from the system.
89If the
90.Fl a
91option is used, all swap devices in
92.Pa /etc/fstab
93will be removed, unless their
94.Dq noauto
95option is also set.
96If the
97.Fl q
98option is used informational messages will not be
99written to standard output when a swap device is removed.
100Note that
101.Nm swapoff
102will fail and refuse to remove a swap device if there is insufficient
103VM (memory + remaining swap devices) to run the system.
104The
105.Nm swapoff
106utility
107must move swapped pages out of the device being removed which could
108lead to high system loads for a period of time, depending on how
109much data has been swapped out to that device.
984263bc 110.Pp
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111The
112.Nm swapctl
113utility exists primarily for those familiar with other
114.Bx Ns s
115and may be
116used to add, remove, or list swap devices.
117Note that the
118.Fl a
119option is used differently in
120.Nm swapctl
121and indicates that a specific list of devices should be added.
122The
123.Fl d
124option indicates that a specific list should be removed.
125The
126.Fl A
127and
128.Fl U
129options to
130.Nm swapctl
131operate on all swap entries in
132.Pa /etc/fstab
133which do not have their
134.Dq noauto
135option set.
136.Pp
137Swap information can be generated using the
138.Xr swapinfo 8
139utility,
140.Nm pstat
141.Fl s ,
142or
143.Nm swapctl
144.Fl l .
145The
146.Nm swapctl
147utility has the following options for listing swap:
148.Bl -tag -width indent
149.It Fl h
150Output values in human-readable form.
151.It Fl g
152Output values in gigabytes.
153.It Fl k
154Output values in kilobytes.
155.It Fl m
156Output values in megabytes.
157.It Fl l
158List the devices making up system swap.
159.It Fl s
160Print a summary line for system swap.
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161.It Fl e
162Attempts to Trim the device if -[Aa] is used.
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163.Pp
164The
165.Ev BLOCKSIZE
166environment variable is used if not specifically
167overridden.
1681K blocks are used by default.
169.El
984263bc 170.Sh FILES
9f3543c6 171.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact
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172.It Pa /dev/{ad,da}?s?b
173standard paging devices
f5ba7fbd 174.It Pa /dev/vn?s?b
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175vnode disk paging device
176.It Pa /etc/fstab
177ASCII filesystem description table
178.It Pa /etc/vntab
179ASCII vnode file table
180.El
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181.Sh DIAGNOSTICS
182These utilities may fail for the reasons described in
183.Xr swapon 2 .
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184.Sh SEE ALSO
185.Xr swapon 2 ,
186.Xr fstab 5 ,
187.Xr init 8 ,
188.Xr pstat 8 ,
189.Xr rc 8 ,
190.Xr vnconfig 8
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191.Sh HISTORY
192The
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193.Nm swapon
194utility appeared in
984263bc 195.Bx 4.0 .
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196The
197.Nm swapoff
198and
199.Nm swapctl
200utilities appeared in
201.Fx 5.1
202and were later ported to
203.Dx 2.7 .