Sometimes a system requires more swap space. There are
three ways to increase swap space: add a new hard drive,
enable swap over NFS
, or create a swap file
on an existing partition.
For information on how to encrypt swap space, which options exist, and why it should be done, refer to Section 19.15, “Encrypting Swap Space”.
Adding a new hard drive for swap gives better performance than adding a partition on an existing drive. Setting up partitions and hard drives is explained in Section 19.3, “Adding Disks” while Section 12.2, “Initial Configuration” discusses partition layouts and swap partition size considerations.
Use swapon(8) to add a swap partition to the system. For example:
#
swapon /dev/ada1s1b
It is possible to use any partition not currently mounted, even if it already contains data. Using swapon(8) on a partition that contains data will overwrite and destroy that data. Make sure that the partition to be added as swap is really the intended partition before running swapon(8).
To automatically add this swap partition on boot, add an
entry to /etc/fstab
:
/dev/ada1s1b
none swap sw 0 0See fstab(5) for an explanation of the entries in
/etc/fstab
.
Swapping over NFS
is only recommended
when there is no local hard disk to swap to.
NFS
swapping will be limited by the
available network bandwidth and puts an additional burden
on nfsd(8).
To create a swap file, specify its size. The following
example creates a 64MB file named
/usr/swap0
.
The GENERIC
kernel already
includes the memory disk driver (md(4)) required
for this operation. When building a custom kernel,
make sure to include the following line in the custom
configuration file:
For information on building a custom kernel, refer to Chapter 9, Configuring the FreeBSD Kernel.
First, create the swapfile
/usr/swap0
:
#
dd if=/dev/zero of=/usr/swap0 bs=1024k count=64
Then, set proper permissions on
/usr/swap0
:
#
chmod 0600 /usr/swap0
Enable the swap file in
/etc/rc.conf
:
Reboot the machine or, to enable the swap file immediately, type:
#
mdconfig -a -t vnode -f /usr/swap0 -u 0 && swapon /dev/md0
All FreeBSD documents are available for download at http://ftp.FreeBSD.org/pub/FreeBSD/doc/
Questions that are not answered by the
documentation may be
sent to <freebsd-questions@FreeBSD.org>.
Send questions about this document to <freebsd-doc@FreeBSD.org>.