Adding More Swap Space
As system configurations change and new software packages are installed, you might need to
add more swap space. The easiest way to add more swap space is
to use the mkfile and swap commands to designate a part of an
existing UFS or NFS file system as a supplementary swap area. These commands,
described in the following sections, enable you to add more swap space without
repartitioning a disk.
Alternative ways to add more swap space are to repartition an existing disk
or to add another disk. For information on how to repartition a
disk, see Chapter 10, Managing Disks (Overview).
Creating a Swap File
The following general steps are involved in creating a swap file:
Creating a swap file by using the mkfile command.
Activating the swap file by using the swap command.
Adding an entry for the swap file in the /etc/vfstab file so that the swap file is activated automatically when the system is booted.
The mkfile command creates a file that is suitable for use as either
an NFS-mounted swap area or a local swap area. The sticky bit is
set, and the file is filled with zeros. You can specify the
size of the swap file in bytes (the default) or in Kbytes, blocks,
or Mbytes by using the k, b, or m suffixes, respectively.
The following table shows the mkfile command options.
Table 21-2 Options to the mkfile Command
Creates an empty file. The
size is noted. However, the disk blocks are not allocated until data is
written to them.
Reports the names and sizes of created files.
Note - Use the -n option only when you create an NFS swap file.
How to Create a Swap File and Make It Available
- Become superuser.
You can create a swap file without root permissions. However, to avoid accidental
overwriting, root should be the owner of the swap file.
- Create a directory for the swap file, if needed.
- Create the swap file.
# mkfile nnn[k|b|m] filename
The swap file of the size nnn (in Kbytes, bytes, or Mbytes) with
the filename you specify is created.
- Activate the swap file.
# /usr/sbin/swap -a /path/filename
You must use the absolute path name to specify the swap file.
The swap file is added and available until the file system is unmounted,
the system is rebooted, or the swap file is removed. Keep in mind
that you cannot unmount a file system while some process or program is
swapping to the swap file.
- Add an entry for the swap file to the /etc/vfstab file that
specifies the full path name of the file, and designates swap as
the file system type.
/path/filename - - swap - no -
- Verify that the swap file is added.
$ /usr/sbin/swap -l
Note - If a swap file does not get activated, make sure that the
following service is running:
# svcs nfs/client
STATE STIME FMRI
enabled 14:14:34 svc:/network/nfs/client:default
Example 21-1 Creating a Swap File and Making It Available
The following examples shows how to create a 100-Mbyte swap file called
# mkdir /files
# mkfile 100m /files/swapfile
# swap -a /files/swapfile
# vi /etc/vfstab
(An entry is added for the swap file):
/files/swapfile - - swap - no -
# swap -l
swapfile dev swaplo blocks free
/dev/dsk/c0t0d0s1 136,1 16 1638608 1600528
/files/swapfile - 16 204784 204784