swapon - Implement encrypted swap
[dragonfly.git] / sbin / swapon / swapon.8
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28.\" @(#)swapon.8 8.1 (Berkeley) 6/5/93
29.\" $FreeBSD: src/sbin/swapon/swapon.8,v 1.15.2.2 2001/12/14 15:17:56 ru Exp $
30.\"
9f3543c6 31.Dd September 7, 2010
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32.Dt SWAPON 8
33.Os
34.Sh NAME
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35.Nm swapon , swapoff , swapctl
36.Nd "specify devices for paging and swapping"
984263bc 37.Sh SYNOPSIS
58b7380e 38.Nm swapon Fl aceiq | Ar
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39.Nm swapoff Fl aq | Ar
40.Nm swapctl
e0fb398b 41.Op Fl AeghklmsU
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42.Oo
43.Fl a Ar
44|
45.Fl d Ar
46.Oc
984263bc 47.Sh DESCRIPTION
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48The
49.Nm swapon , swapoff
50and
51.Nm swapctl
52utilities are used to control swap devices in the system.
53At boot time all swap entries in
54.Pa /etc/fstab
55are added automatically when the system goes multi-user.
56Swap devices use a fixed interleave; the maximum number of devices
57is specified by the kernel configuration option
58.Dv NSWAPDEV ,
59which is typically set to 4.
60There is no priority mechanism.
984263bc 61.Pp
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62The
63.Nm swapon
64utility adds the specified swap devices to the system.
65If the
66.Fl a
67option is used, all swap devices in
984263bc 68.Pa /etc/fstab
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69will be added.
70The following options are supported:
71.Bl -tag -width indent
72.It Dq noauto
73The device is ignored and will not be added or removed with this option.
74.It Dq crypt
75Swap will be encrpted with a random key using a /dev/mapper name of
76swap-<device> ,
77for example 'swap-da0s1b'.
78This will also load the dm_target_crypt module if necessary.
79.It Dq trim
80Swap will be TRIMed if the device supports it, otherwise this option
81will be ignored.
82.El
83.Pp
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84If the
85.Fl q
86option is used informational messages will not be
87written to standard output when a swap device is added.
e0fb398b 88If the
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89.Fl c
90option is used, the device will be encrypted with a random
91key.
92If the
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93.Fl e
94option is used, the device will be trimmed if
95it supports trim and the trim_enabled sysctl is on.
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96The
97.Fl i
98option asks user confirmation before adding a swap device.
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99.Pp
100The
101.Nm swapoff
102utility removes the specified swap devices from the system.
103If the
104.Fl a
105option is used, all swap devices in
106.Pa /etc/fstab
107will be removed, unless their
108.Dq noauto
109option is also set.
110If the
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111.Fl c
112option is used the device is mapped to the appropriate crypto device
113and the crypto device is removed as well.
114If this option is specified in
115.Nm swapon
116then it should also be specified in
117.Nm swapoff .
118If the
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119.Fl q
120option is used informational messages will not be
121written to standard output when a swap device is removed.
122Note that
123.Nm swapoff
124will fail and refuse to remove a swap device if there is insufficient
125VM (memory + remaining swap devices) to run the system.
126The
127.Nm swapoff
128utility
129must move swapped pages out of the device being removed which could
130lead to high system loads for a period of time, depending on how
131much data has been swapped out to that device.
984263bc 132.Pp
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133The
134.Nm swapctl
135utility exists primarily for those familiar with other
136.Bx Ns s
137and may be
138used to add, remove, or list swap devices.
139Note that the
140.Fl a
141option is used differently in
142.Nm swapctl
143and indicates that a specific list of devices should be added.
144The
145.Fl d
146option indicates that a specific list should be removed.
147The
148.Fl A
149and
150.Fl U
151options to
152.Nm swapctl
153operate on all swap entries in
154.Pa /etc/fstab
155which do not have their
156.Dq noauto
157option set.
158.Pp
159Swap information can be generated using the
160.Xr swapinfo 8
161utility,
162.Nm pstat
163.Fl s ,
164or
165.Nm swapctl
166.Fl l .
167The
168.Nm swapctl
169utility has the following options for listing swap:
170.Bl -tag -width indent
171.It Fl h
172Output values in human-readable form.
173.It Fl g
174Output values in gigabytes.
175.It Fl k
176Output values in kilobytes.
177.It Fl m
178Output values in megabytes.
179.It Fl l
180List the devices making up system swap.
181.It Fl s
182Print a summary line for system swap.
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183.If Fl c
184The swap is or should be crypted.
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185.It Fl e
186Attempts to Trim the device if -[Aa] is used.
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187.It Fl i
188Asks user confirmation when -a is used.
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189.It Fl q
190Less noisy output.
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191.Pp
192The
193.Ev BLOCKSIZE
194environment variable is used if not specifically
195overridden.
1961K blocks are used by default.
197.El
984263bc 198.Sh FILES
9f3543c6 199.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact
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200.It Pa /dev/{ad,da}?s?b
201standard paging devices
f5ba7fbd 202.It Pa /dev/vn?s?b
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203vnode disk paging device
204.It Pa /etc/fstab
205ASCII filesystem description table
206.It Pa /etc/vntab
207ASCII vnode file table
208.El
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209.Sh DIAGNOSTICS
210These utilities may fail for the reasons described in
211.Xr swapon 2 .
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212.Sh SEE ALSO
213.Xr swapon 2 ,
214.Xr fstab 5 ,
215.Xr init 8 ,
216.Xr pstat 8 ,
217.Xr rc 8 ,
218.Xr vnconfig 8
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219.Sh HISTORY
220The
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221.Nm swapon
222utility appeared in
984263bc 223.Bx 4.0 .
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224The
225.Nm swapoff
226and
227.Nm swapctl
228utilities appeared in
229.Fx 5.1
230and were later ported to
231.Dx 2.7 .