Hello, i had a second hard installed on my server a month or so ago, on it i was created a second swap partiton of 256mb. This swap partition has never initialized, not much o f a problem as my swap usgae was low. However i got up this morning to find all my swap used.
Swapon is used to specify devices on which paging and
swapping are to take place. Calls to swapon normally
occur in the system multi-user initialization file /etc/rc
making all swap devices available, so that the paging and
swapping activity is interleaved across several devices
Normally, the first form is used:
-h Provide help
-V Display version
-s Display swap usage summary by device. This option
is only available if /proc/swaps exists (probably
not before kernel 2.1.25).
-a All devices marked as ``sw'' swap devices in
/etc/fstab are made available. Devices that are
already running as swap are silently skipped.
-e When -a is used with swapon, -e makes swapon
silently skip devices that do not exist.
Specify priority for swapon. This option is only
available if swapon was compiled under and is used
under a 1.3.2 or later kernel. priority is a value
between 0 and 32767. See swapon(2) for a full
description of swap priorities. Add pri=value to
the option field of /etc/fstab for use with swapon
Swapoff disables swapping on the specified devices and
files, or on all swap entries in /etc/fstab when the -a
flag is given.
After creating the swap area, you need the swapon command to start using it. Usually swap areas are listed in /etc/fstab so that they can be taken into use at boot timeby a swapon -a command in some boot script.
The device argument will usually be a disk partition
(something like /dev/hda4 or /dev/sdb7) but can also be a
file. The Linux kernel does not look at partition Id's,
but many installation scripts will assume that partitions
of hex type 82 (LINUX_SWAP) are meant to be swap parti*
tions. (Warning: Solaris also uses this type. Be careful
not to kill your Solaris partitions.)
The size parameter is superfluous but retained for back*
wards compatibility. (It specifies the desired size of
the swap area in 1024-byte blocks. mkswap will use the
entire partition or file if it is omitted. Specifying it
is unwise - a typo may destroy your disk.)
The PSZ parameter specifies the page size to use. It is
almost always unnecessary (even unwise) to specify it, but
certain old libc versions lie about the page size, so it
is possible that mkswap gets it wrong. The symptom is that
a subsequent swapon fails because no swap signature is
found. Typical values for PSZ are 4096 or 8192.
Linux knows about two styles of swap areas, old style and
new style. The last 10 bytes of the first page of the
swap area distinguishes them: old style has `SWAP_SPACE',
new style has `SWAPSPACE2' as signature.
In the old style, the rest of this first page was a bit
map, with a 1 bit for each usable page of the swap area.
Since the first page holds this bit map, the first bit is
0. Also, the last 10 bytes hold the signature. So, if the
page size is S, an old style swap area can describe at
most 8*(S-10)-1 pages used for swapping. With S=4096 (as
on i386), the useful area is at most 133890048 bytes
(almost 128 MiB), and the rest is wasted. On an alpha and
sparc64, with S=8192, the useful area is at most 535560992
bytes (almost 512 MiB).
The old setup wastes most of this bitmap page, because
zero bits denote bad blocks or blocks past the end of the
swap space, and a simple integer suffices to indicate the
size of the swap space, while the bad blocks, if any, can
simply be listed. Nobody wants to use a swap space with
hundreds of bad blocks. (I would not even use a swap space
with 1 bad block.) In the new style swap area this is
precisely what is done. The maximum useful size of a swap
area now depends on the architecture. It is roughly 2GiB
on i386, PPC, m68k, ARM, 1GiB on sparc, 512MiB on mips,
128GiB on alpha and 3TiB on sparc64.
Note that before 2.1.117 the kernel allocated one byte for
each page, while it now allocates two bytes, so that tak*
ing a swap area of 2 GiB in use might require 2 MiB of
Presently, Linux allows 8 swap areas. The areas in use can
be seen in the file /proc/swaps (since 2.1.25).
mkswap refuses areas smaller than 10 pages.
If you don't know the page size that your machine uses,
you may be able to look it up with "cat /proc/cpuinfo" (or
you may not - the contents of this file depend on archi*
tecture and kernel version).
To setup a swap file, it is necessary to create that file
before initializing it with mkswap , e.g. using a command
# dd if=/dev/zero of=swapfile bs=1024 count=65536
Note that a swap file must not contain any holes (so,
using cp(1) to create the file is not acceptable).
-c Check the device (if it is a block device) for bad
blocks before creating the swap area. If any are
found, the count is printed.
-f Force - go ahead even if the command is stupid.
This allows the creation of a swap area larger than
the file or partition it resides on. On SPARC,
force creation of the swap area. Without this
option mkswap will refuse to create a v0 swap on a
device with a valid SPARC superblock, as that prob*
ably means one is going to erase the partition
-p PSZ Specify the page size to use.
-v0 Create an old style swap area.
-v1 Create a new style swap area.
If no -v option is given, mkswap will default to new
style, but use old style if the current kernel is older
than 2.1.117 (and also if PAGE_SIZE is less than 2048).
The new style header does not touch the first block, so
may be preferable, in case you have a boot loader or disk
label there. If you need to use both 2.0 and 2.2 kernels,
use the -v0 option when creating the swapspace.
Don't worry about the above so much that's the man page for mkswap, it's more info than you need. You'll get there...
I assume when you said that you created another swap partition in the original message that you did give it a linux swap type - 82(in hex), correct? If not you'll need to change it. You created it, so I'm going to assume you'd know how to change the partition type.
If so, then yes go ahead and do the mkswap on your new swap partition. Don't worry about the comandline options. mkswap itself will take care of that for you. Once it's initialized, you can activate it with swapon. Be careful to use the correct /dev/hd??? device. mkswap is like a format in a way. You can lose data if you use the wrong one.
It should mount automatically on boot. In the /etc/fstab entry you showed above, you included "defaults" for the options parameter. One of the things included with defaults option is "auto" which mounts it on boot.
auto - auto mount on boot
rw - read and write
suid - user/group ownership bits
exec - permit executables
dev - interpret block or character devices
async - asynchronous i/o
(think that's it - did I forget any???)
Edit - yes I did...
nouser - only root can mount fs