Using Linux in RAM... - Setup

This is a discussion on Using Linux in RAM... - Setup ; I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially making the disk read-only. Can anyone point me to some instructs for this? Thanks....

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Thread: Using Linux in RAM...

  1. Using Linux in RAM...

    I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially
    making the disk read-only. Can anyone point me to some instructs for this?

    Thanks.

  2. Re: Using Linux in RAM...

    Christian Williamson wrote:
    > I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially
    > making the disk read-only. Can anyone point me to some instructs for this?
    >
    > Thanks.

    well making a ramdisk and using it for swap is not hard..

    I am less sure about other processes that use disk..I guess you could
    have a /tmp in ramdisk as well..and log files..well a patch to syslog to
    make it either junk log files or write them to somewhere else would be
    called for.


    I take it this is for a very stripped down specific application?


  3. Re: Using Linux in RAM...

    Hello,

    The Natural Philosopher a écrit :
    >
    > well making a ramdisk and using it for swap is not hard..


    And is definitely totally useless.

    PS : what does this have to do with networking ?

  4. Re: Using Linux in RAM...

    The Natural Philosopher wrote:
    > Christian Williamson wrote:
    >> I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially
    >> making the disk read-only. Can anyone point me to some instructs for
    >> this?
    >>
    >> Thanks.

    > well making a ramdisk and using it for swap is not hard..
    >
    > I am less sure about other processes that use disk..I guess you could
    > have a /tmp in ramdisk as well..and log files..well a patch to syslog to
    > make it either junk log files or write them to somewhere else would be
    > called for.
    >
    >
    > I take it this is for a very stripped down specific application?


    I haven't stripped it down. I ran a script to see how many files were
    changed from boot, and it ended up being over 34,000 files, 26,000 of
    them in /proc. See
    http://www.mydigitallife.info/2006/0...e-ago-in-unix/
    for the find command.

    I'd like to boot from the disk as if it's read-only, then run everything
    out of ram.

  5. Re: Using Linux in RAM...

    The Natural Philosopher wrote:
    > Christian Williamson wrote:
    >> I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially
    >> making the disk read-only. Can anyone point me to some instructs for
    >> this?
    >>
    >> Thanks.

    > well making a ramdisk and using it for swap is not hard..
    >
    > I am less sure about other processes that use disk..I guess you could
    > have a /tmp in ramdisk as well..and log files..well a patch to syslog to
    > make it either junk log files or write them to somewhere else would be
    > called for.
    >
    >
    > I take it this is for a very stripped down specific application?


    I haven't stripped it down. I ran a script to see how many files were
    changed from boot, and it ended up being over 34,000 files, 26,000 of
    them in /proc. See
    http://www.mydigitallife.info/2006/0...e-ago-in-unix/
    for the find command.

    I'd like to boot from the disk as if it's read-only, then run everything
    out of ram.

  6. Re: Using Linux in RAM...

    Pascal Hambourg wrote:
    > Hello,
    >
    > The Natural Philosopher a écrit :
    >>
    >> well making a ramdisk and using it for swap is not hard..

    >
    > And is definitely totally useless.
    >


    Why? if the OS wants to see swap, give it some..it may be happier that
    way than simply removing swap altogether.


    > PS : what does this have to do with networking ?


    no idea. I fund it in linux group..ah - cross posted.

    Sorry about that.

    I didn;t notice.

  7. Re: Using Linux in RAM...

    Pascal Hambourg wrote:
    > Hello,
    >
    > The Natural Philosopher a écrit :
    >>
    >> well making a ramdisk and using it for swap is not hard..

    >
    > And is definitely totally useless.
    >
    > PS : what does this have to do with networking ?


    I could boot over the network and place everything in ramdisk.

  8. Re: Using Linux in RAM...

    The Natural Philosopher a écrit :
    >>
    >>> well making a ramdisk and using it for swap is not hard..

    >>
    >> And is definitely totally useless.

    >
    > Why? if the OS wants to see swap, give it some..it may be happier that
    > way than simply removing swap altogether.


    Why would the system want to see swap ? Linux does not need swap to
    operate. AFAIK, swap space may be used for two reasons.

    1) Free some RAM for processes or disk cache. Obviously, creating swap
    space in RAM won't free any RAM. On the contrary, it will consume some
    RAM even though swap is not needed.

    2) Suspend-to-disk. Obviously again, swap space in RAM cannot be used
    for this.

  9. Re: Using Linux in RAM...

    Christian Williamson a écrit :
    >
    > I could boot over the network and place everything in ramdisk.


    If you want to boot over the network then say it explicitly because it
    is a specific matter.

    If you want to boot from a local read-only medium, you may want to
    consider UnionFS . It allows to
    merge read-only (local medium) and read-write (ramdisk or tmpfs)
    filesystems into one read-write filesystem. This is used by some Live
    CDs in order to save RAM.

  10. Re: Using Linux in RAM...

    Pascal Hambourg wrote:
    > Christian Williamson a écrit :
    >>
    >> I could boot over the network and place everything in ramdisk.

    >
    > If you want to boot over the network then say it explicitly because it
    > is a specific matter.
    >
    > If you want to boot from a local read-only medium, you may want to
    > consider UnionFS . It allows to
    > merge read-only (local medium) and read-write (ramdisk or tmpfs)
    > filesystems into one read-write filesystem. This is used by some Live
    > CDs in order to save RAM.


    Thanks. BTW, Pascal, which group do you think I should I have posted the
    original in?

  11. Re: Using Linux in RAM...

    "Christian Williamson" wrote
    > The Natural Philosopher wrote:
    >> Christian Williamson wrote:
    >>> I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially
    >>> making the disk read-only. Can anyone point me to some instructs for
    >>> this?
    >>>
    >>> Thanks.

    >> well making a ramdisk and using it for swap is not hard..
    >>
    >> I am less sure about other processes that use disk..I guess you could
    >> have a /tmp in ramdisk as well..and log files..well a patch to syslog to
    >> make it either junk log files or write them to somewhere else would be
    >> called for.
    >>
    >>
    >> I take it this is for a very stripped down specific application?

    >
    > I haven't stripped it down. I ran a script to see how many files were
    > changed from boot, and it ended up being over 34,000 files, 26,000 of
    > them in /proc. See


    Um .... I thought files in /proc were not actually stored on the disk??


  12. Re: Using Linux in RAM...

    Magnate wrote:
    > "Christian Williamson" wrote
    >> The Natural Philosopher wrote:
    >>> Christian Williamson wrote:
    >>>> I've got Fedora 9 on my pc, and I want to run it out of RAM,
    >>>> essentially
    >>>> making the disk read-only. Can anyone point me to some instructs for
    >>>> this?
    >>>>
    >>>> Thanks.
    >>> well making a ramdisk and using it for swap is not hard..
    >>>
    >>> I am less sure about other processes that use disk..I guess you could
    >>> have a /tmp in ramdisk as well..and log files..well a patch to syslog to
    >>> make it either junk log files or write them to somewhere else would be
    >>> called for.
    >>>
    >>>
    >>> I take it this is for a very stripped down specific application?

    >>
    >> I haven't stripped it down. I ran a script to see how many files were
    >> changed from boot, and it ended up being over 34,000 files, 26,000 of
    >> them in /proc. See

    >
    > Um .... I thought files in /proc were not actually stored on the disk??

    I dont think they are..

  13. Re: Using Linux in RAM...

    Pascal Hambourg wrote:
    > The Natural Philosopher a écrit :
    >>>
    >>>> well making a ramdisk and using it for swap is not hard..
    >>>
    >>> And is definitely totally useless.

    >>
    >> Why? if the OS wants to see swap, give it some..it may be happier that
    >> way than simply removing swap altogether.

    >
    > Why would the system want to see swap ? Linux does not need swap to
    > operate. AFAIK, swap space may be used for two reasons.
    >


    Well if it doesn't then of course that is a useless suggestion..I
    thought it needed it there, even if it didn't use it.

  14. Re: Using Linux in RAM...

    On Thu, 18 Sep 2008 10:44:38 +0100, The Natural Philosopher wrote:
    > well making a ramdisk and using it for swap is not hard..


    Using ram for a swap file is insanity. You're basically setting up the
    ram to simulate a block device so that you can use it to simulate ram!

    Just run with enough memory and no swap file. Linux uses shared libraries
    like swap; it'll drop unused pages knowing that it can always return to the
    libraries to reload them.

    The only concern I have is that linux may use too much ram for disk buffering
    and not leave import application pages resident.

  15. Re: Using Linux in RAM...

    On Thu, 18 Sep 2008 08:31:57 +0000, Christian Williamson wrote:

    > I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially
    > making the disk read-only. Can anyone point me to some instructs for this?
    >
    > Thanks.
    >

    This works in theory. Practical limits may be another matter, though.
    Certain rescue environments work in RAM because they are small enough to
    fit while leaving enough free memory for the OS to use as RAM. The problem
    comes with the magnitude of a full install of a modern GNU/Linux. I
    do not use FC 9, but I assume a full install consumes over 4G of hard
    disk space. If that is written to RAM, then it might work (in theory) if
    your box has 5G or more RAM (leaving 1G for the OS itself). In addition to
    the full amount of RAM, you also need a motherboard capable of using
    the RAM, and a PAE enabled kernel (for a 32-bit kernel), or if you have
    compatible hardware then a 64-bit kernel be used.

    Other options...
    1. If you have the RAM, then I guess your initrd can be your root
    filesystem. There will be some delay as the initrd is read into RAM at
    boot. There could also be some size limits for the initrd which I am not
    aware of. I have only used initrd's which were less than 256M.

    2. You can have a root filesystem on tmpfs. IIRC, tmpfs uses half of
    available RAM by default. There is an IBM article written by Robbins on
    the topic.
    http://www.ibm.com/developerworks/library/l-fs3.html

    3. An easier "performance" solution is to get the fastest read media
    available. 8G of flash memory is very affordable now. It has the
    advantage over your method (AIUI) in that the storage is local and does
    not need not be transmitted for each new boot. Only the portions of the
    filesystem which are used are ever placed in memory at all, etc.

    --
    Douglas Mayne


  16. Re: Using Linux in RAM...

    On 2008-09-18, Christian Williamson wrote:

    > I've got Fedora 9 on my pc, and I want to run it out of RAM,
    > essentially making the disk read-only. Can anyone point me to
    > some instructs for this?


    What you're describing is generally referred to as a "livecd".

    If you're interested in building one of your own, then Google
    for "build linux livecd".

    If you just want to download one and run from it, then just go
    to distrowatch and download one.

    --
    Grant Edwards grante Yow! I like the way ONLY
    at their mouths move ... They
    visi.com look like DYING OYSTERS

  17. Re: Using Linux in RAM...

    Christian Williamson writes:

    > I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially
    > making the disk read-only. Can anyone point me to some instructs for this?


    Once I did something similar but with Debian. The machine was a
    diskless box, and it booted over the network. Then it mounted a
    root partition through nfs, created a local filesystem (AFAIR
    it was tmpfs), copied the root to this new fs in ram, pivot
    root, umount nfsroot, etc. It even ran X out of ram.

    The good thing about this is that it is very easy to add a cloned
    machined to the network. (which is very useful in a regulated
    environment). There is no worry about backing up root partitions
    and restoring if a machine/disk fails. The nfs server can be
    a simple default linux install with dhcp/nfs enabled, and all
    you need to worry about is the backup of some config files and
    the exported root directory structure. Very easy to restore in
    case of a disaster.

    The downside is that ram is wasted. However, today ram is
    cheap, and after a good pruning, I cut down the root partition
    to a very reasonable size.

    Another downside is that you will go through a lot of misery,
    and it is not something that somebody can really help you
    from a remote location at the beginning, when help is actually
    needed. The upside is that you will learn a lot.

    Vilmos

  18. Re: Using Linux in RAM...

    "Magnate" writes:

    >
    > Um .... I thought files in /proc were not actually stored on the
    > disk??


    That's correct. Every piece of hardware in UNIX is accessed through a
    filename. In particular, /proc is a special filesystem:

    #
    proc /proc proc defaults 0 0

    See proc(5)

    The proc filesystem is a pseudo-filesystem which is used as an inter-
    face to kernel data structures. It is commonly mounted at /proc. Most
    of it is read-only, but some files allow kernel variables to be
    changed.

  19. Re: Using Linux in RAM...

    On Thu, 18 Sep 2008, Christian Williamson wrote:

    > I've got Fedora 9 on my pc, and I want to run it out of RAM, essentially
    > making the disk read-only. Can anyone point me to some instructs for this?
    >

    Maybe you should be more descriptive about what you want to do,
    because it looks like this thread has gone off on a tangent, though
    who knows.

    Linux always runs out of RAM, the kernel is loaded, which then in
    turn loads some other things and then you get a prompt, from where
    you can load other things.

    Hence it's not clear if you are asking for hints on dealing with
    no writes to the hard drive, or if you are asking about something
    else.

    If you are asking about running Linux normally, then the issue
    becomes turning off things like logging, and other things that
    routinely write to disk, and then figure out how to deal with
    things you need to save when the computer turns off.

    An obvious example of this is the EEEPC, where it runs like
    any Linux, but lacks a hard drive so you want to keep writes
    down to a minimum. So logging is turned off (so I gather) and
    yet when it's time to save a document, it gets written to the
    flash drive that is the stand in for a hard drive.

    I'm sure this sort of thing has been documented, but I can't
    say where.

    Michael


  20. Re: Using Linux in RAM...

    Christian Williamson a écrit :
    >
    > Thanks. BTW, Pascal, which group do you think I should I have posted the
    > original in?


    Sorry, I don't know the comp.os.linux.* hierarchy well enough to answer
    this question.

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