Results 1 to 10 of 10
  1. #1

    second swap aprtition initilization

    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.

    so, how can i get this new swap inititialized ?


  2. #2
    Join Date
    Jul 2001
    Troy, Missouri USA


    Swapon should work;

    swapon, swapoff - enable/disable devices and files for
    paging and swapping

    /sbin/swapon [-h -V]
    /sbin/swapon -a [-v] [-e]
    /sbin/swapon [-v] [-p priority] specialfile ...
    /sbin/swapon [-s]
    /sbin/swapoff [-h -V]
    /sbin/swapoff -a
    /sbin/swapoff specialfile ...

    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
    and files.

    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.

    -p priority
    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.

  3. #3
    Thanks for reply,

    i did:
    /sbin/swapon -a

    got error message:
    swapon: /dev/hdd3: Invalid argument

    i then did /sbin/swapon -s and got:
    Filename Type Size Used Priority
    /dev/hda8 partition 265032 0 0

    fstab shows:

    /dev/hda8 swap swap defaults,pri=0 0 0
    /dev/hdd3 swap swap defaults,pri=0 0 0

    any ideas


  4. #4
    Join Date
    Jul 2002
    The Big Easy -New Orleans
    Did you do a mkswap?
    Lagniappe Internet L.L.C. - Wholesale Reseller and VPS Hosting.
    Lagniappe (lan-yap) - An extra or unexpected gift or benefit.
    HostEntrepreneur - Hosting news, reviews, tips, tricks, help and the occassional rant

  5. #5

    so do i do

    mkswap /dev/hdd3


    /sbin/swapon -a

  6. #6
    Join Date
    Jul 2001
    Troy, Missouri USA
    mkswap [-c] [-vN] [-f] [-p PSZ] device [size]

    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
    kernel memory.

    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.

  7. #7


    Thanks for your very in depth reply, but i am no wiser

    I will come back in few hours and re-read this, might become clearer.

  8. #8
    Join Date
    Jul 2002
    The Big Easy -New Orleans
    Sorry I was in a bit of a rush before...

    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.

    That should do you.

  9. #9
    cheers dude, worked a treat

    will it now do it automatically if i have to reboot or will i have to go through process again?

  10. #10
    Join Date
    Jul 2002
    The Big Easy -New Orleans
    Glad it worked for you.

    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.

    defaults includes:
    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

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts