.TH SWAP 8
.SH NAME
swap \- establish a swap file
.SH SYNOPSIS
.B swap
.I file 
.SH DESCRIPTION
.I Swap
establishes a file or device for the system to swap on.
If
.I file
is a device, the device is used directly; if a directory,
a unique file is created in that directory on which to swap.
The environment variable
.B swap
is set to the full name of the resulting file.
The number of blocks available in the file or device
must be at least the number of swap blocks configured
at system boot time.
.PP
If a swap channel has already been set and no blocks
are currently valid in the file the old file will be
closed and then replaced. If any blocks are valid on
the device an error is returned instead.
.SH SOURCE
.B /sys/src/cmd/swap.c
.SH BUGS
Swapping to a file served by a user-level process, such as
.IR kfs (4),
can lead to deadlock; use raw devices or remote files instead.