Linux Compact Flash Write Filter akin to XPe EWF - Embedded

This is a discussion on Linux Compact Flash Write Filter akin to XPe EWF - Embedded ; Hi, i'm looking for a Linux equivalent of Windows XPe Enhanced Write Filter, which basically will write all system changes to a ram disk which can, if required, be committed to disk by the user via a write utility. If ...

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Thread: Linux Compact Flash Write Filter akin to XPe EWF

  1. Linux Compact Flash Write Filter akin to XPe EWF

    Hi, i'm looking for a Linux equivalent of Windows XPe Enhanced Write
    Filter, which basically will write all system changes to a ram disk
    which can, if required, be committed to disk by the user via a write
    utility. If power is removed and changes not committed to disk all
    changes will be lost.

    The reason i am after this is because i wish to run Linux on compact
    flash. I have been messing around with pfsense firewall but it
    transpires i need something a bit more flexible, a Linux based install
    which can run on compact flash with minimal disk writes to compact
    flash to ensure the CF card doesn't die, but also with the ability to
    update the file system and install custom packages, install from
    source etc.

    It would be ideal to have BSD (ok not linux but dont want to get OT
    here), CentOS or similair running on CF card, i know people talk about
    make the file system Read Only but then that has issues with certain
    packages in the system that need write access, would be nice if these
    changes could be committed one as off writes.

    Have searched for a compact flash enabled distribution but with the
    benefits and flexibility of installing packages via apt-get etc but
    cannot find one, hence my idea that a write filter driver which could
    sit in between the CF card and IDE driver would be great... then i
    would get the benefit of both worlds.

    Any ideas? Any recommendations to a an existing CF based linux distro
    would be great, but as this is for a number of router boxes that need
    to be up and running in a short space of time i dont want to spend too
    much time on the development side of it. Plug and play write filter
    driver would be best.

    Many thanks in advance,

    Chris

  2. Re: Linux Compact Flash Write Filter akin to XPe EWF

    Chris Morley wrote:
    > Hi, i'm looking for a Linux equivalent of Windows XPe Enhanced Write
    > Filter, which basically will write all system changes to a ram disk
    > which can, if required, be committed to disk by the user via a write
    > utility. If power is removed and changes not committed to disk all
    > changes will be lost.
    >
    > The reason i am after this is because i wish to run Linux on compact
    > flash. I have been messing around with pfsense firewall but it
    > transpires i need something a bit more flexible, a Linux based install
    > which can run on compact flash with minimal disk writes to compact
    > flash to ensure the CF card doesn't die, but also with the ability to
    > update the file system and install custom packages, install from
    > source etc.
    >
    > It would be ideal to have BSD (ok not linux but dont want to get OT
    > here), CentOS or similair running on CF card, i know people talk about
    > make the file system Read Only but then that has issues with certain
    > packages in the system that need write access, would be nice if these
    > changes could be committed one as off writes.
    >
    > Have searched for a compact flash enabled distribution but with the
    > benefits and flexibility of installing packages via apt-get etc but
    > cannot find one, hence my idea that a write filter driver which could
    > sit in between the CF card and IDE driver would be great... then i
    > would get the benefit of both worlds.
    >
    > Any ideas? Any recommendations to a an existing CF based linux distro
    > would be great, but as this is for a number of router boxes that need
    > to be up and running in a short space of time i dont want to spend too
    > much time on the development side of it. Plug and play write filter
    > driver would be best.
    >
    > Many thanks in advance,
    >
    > Chris


    If you are looking for firewall/router type distributions, there are a
    number of Linux-based distros (openwrt, SmoothWall, IPCop, etc.).

    I don't expect you will find anything like the EWF you describe for
    Linux - you don't need it. XPe would need something like that because
    it writes all sorts of junk to different places in the file system
    (especially the registry) even while it's doing nothing of interest.
    With Linux, there is a much clearer modularisation in the file system,
    so it is easy to put parts in a ram disk (especially tmpfs) if you don't
    want to write to a flash disk. If you put /tmp, /var/log, and /var/lock
    on tmpfs, there is little that will be written to the disk except what
    you want to write.

  3. Re: Linux Compact Flash Write Filter akin to XPe EWF

    On 6 Mar, 20:38, David Brown
    wrote:
    > Chris Morley wrote:
    > > Hi, i'm looking for a Linux equivalent of Windows XPe Enhanced Write
    > > Filter, which basically will write all system changes to a ram disk
    > > which can, if required, be committed to disk by the user via a write
    > > utility. If power is removed and changes not committed to disk all
    > > changes will be lost.

    >
    > > The reason i am after this is because i wish to run Linux on compact
    > > flash. I have been messing around with pfsense firewall but it
    > > transpires i need something a bit more flexible, a Linux based install
    > > which can run on compact flash with minimal disk writes to compact
    > > flash to ensure the CF card doesn't die, but also with the ability to
    > > update the file system and install custom packages, install from
    > > source etc.

    >
    > > It would be ideal to have BSD (ok not linux but dont want to get OT
    > > here), CentOS or similair running on CF card, i know people talk about
    > > make the file system Read Only but then that has issues with certain
    > > packages in the system that need write access, would be nice if these
    > > changes could be committed one as off writes.

    >
    > > Have searched for a compact flash enabled distribution but with the
    > > benefits and flexibility of installing packages via apt-get etc but
    > > cannot find one, hence my idea that a write filter driver which could
    > > sit in between the CF card and IDE driver would be great... then i
    > > would get the benefit of both worlds.

    >
    > > Any ideas? Any recommendations to a an existing CF based linux distro
    > > would be great, but as this is for a number of router boxes that need
    > > to be up and running in a short space of time i dont want to spend too
    > > much time on the development side of it. Plug and play write filter
    > > driver would be best.

    >
    > > Many thanks in advance,

    >
    > > Chris

    >
    > If you are looking for firewall/router type distributions, there are a
    > number of Linux-based distros (openwrt, SmoothWall, IPCop, etc.).
    >
    > I don't expect you will find anything like the EWF you describe for
    > Linux - you don't need it. *XPe would need something like that because
    > it writes all sorts of junk to different places in the file system
    > (especially the registry) even while it's doing nothing of interest.
    > With Linux, there is a much clearer modularisation in the file system,
    > so it is easy to put parts in a ram disk (especially tmpfs) if you don't
    > want to write to a flash disk. *If you put /tmp, /var/log, and /var/lock
    > on tmpfs, there is little that will be written to the disk except what
    > you want to write.- Hide quoted text -
    >
    > - Show quoted text -


    Thanks for the reply, i have been through them all... i use OpenWRT on
    WRT 54G hardware and its excellent. However its not supported on x86
    as thats beta. I have used Smoothwall, IPCop, M0n0Wall and eventually
    used pfsense which is the most flexible however it seems to have
    issues with site to site OpenVPN and isnt as flexible as i would like.

    I could chuck on a full version of Linux on a real harddisk however i
    would be concerned of reliability issues if the drive died as this is
    for a rotuer. To this end, i have found Voyage Linux, an embedded
    Debian install which has support for apt and committable file system
    thus preserving the file system life. Looks good will check it out.
    Hopefully i can have the best of both worlds!

    Regards,

    Chris

  4. Re: Linux Compact Flash Write Filter akin to XPe EWF

    Chris Morley wrote:

    > Thanks for the reply, i have been through them all... i use OpenWRT on
    > WRT 54G hardware and its excellent. However its not supported on x86
    > as thats beta. I have used Smoothwall, IPCop, M0n0Wall and eventually
    > used pfsense which is the most flexible however it seems to have
    > issues with site to site OpenVPN and isnt as flexible as i would like.
    >
    > I could chuck on a full version of Linux on a real harddisk however i
    > would be concerned of reliability issues if the drive died as this is
    > for a rotuer. To this end, i have found Voyage Linux, an embedded
    > Debian install which has support for apt and committable file system
    > thus preserving the file system life. Looks good will check it out.
    > Hopefully i can have the best of both worlds!
    >


    I haven't tried Voyage Linux myself, although I've read a little about it.

    If you want to avoid hard disk wear for long-term reliability (although
    personally I have very seldom seen hard disk failures, even on machines
    with a decade of hard service), you might consider using one of the
    newer generation of flash disks with standard hard disk interfaces.
    They cost a lot more per GB than normal hard disks, but you don't need a
    large one for a router. Their MTBF is much higher than for rotating
    disks, and you won't meet wear issues unless you specifically
    continuously write huge amounts of data to them.

    Other alternatives include using a distribution with no read-write media
    at all. There are distros aimed at loading all the required software
    from a CD or even a floppy, the loading their configuration from USB or
    floppy, and keeping everything in memory rather than on disk. Obviously
    that's a bit more awkward for configuration changes, and you need to
    store your logs on an external machine, but they are great from a
    security viewpoint - if the machine ever gets compromised, a reboot will
    guaranteed restore the setup.

    For the ultimate in low disk usage (and security), I remember reading an
    article about running a Linux router in halt mode. Even when halted,
    the kernel still passed network packets through the filter and routing
    tables, but no file systems are mounted, and no processes can run (this
    was on an earlier version of Linux - perhaps 2.0 or 2.2, and may not
    work on more modern kernels).

    mvh.,

    David

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