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Thread: Why would the running knoppix partition be mounted rw?

  1. #11
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    Something that might be tried

    I think this might be tried:

    1. On startup, if persistent not empty, copy persistent content to ramdisk, run with ramdisk. Otherwise, swap KNOPPIX.sq and KNOPPIX_b.sq, run from KNOPPIX.sq
    2. During running, use two (script) commands: ramdisk_save and ramdisk_commit. ramdisk_save saves to a overlayfs mount of knoppix-data.img and KNOPPIX.sq, unmounting afterwards.
    3. ramdisk_commit first performs a ramdisk_save, then compresses the overlayfs mount to KNOPPIX_b.sq, unmounts and clears knoppix-data.img.
    4. Unless otherwise requested, KNOPPIX_b.sq will be renamed to KNOPPIX.sq and used at next startup, the old KNOPPIX.sq becoming KNOPPIX_b.sq and usable as a backup until next commit.
    5. Cheatcode revert either aborts the swapping after a commit, or works with the oldest squashfs image available.

    This way, we never use the persistence for daily work, we just save to it. There is not much complexity added to minirt init either: Copying and possibly image swapping, using noimage setup. With the revert cheatcode, KNOPPIX.sq and KNOPPIX_b.sq are swapped, if KNOPPX.sq is not already the oldest.

    With FAT32 limits, this could be done within ca 12GB space if mksquashfs can use a pipe. Otherwise, ca 12 GB extra is needed for filesystem copy. When a 32GB USB3 stick costs about $20, I don't think an extra 16GB is that much to care about. I would guess ca 2GB persistent store would be fine with this setup, and starting from DVD Knoppix slimmed down to ca 3GB (example of purging procedure provided elsewhere), the should be enough workspace for many needs. Even when the least efficient squashfs compression is used.

    And using NTFS or ext3 file system, the 4GB limit does of course not apply.

  2. #12
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    @ Capricorny

    We are about on the same wavelength, but I think for my purposes, that
    I don't need a full re-mastering which I think your last list implies.
    I have in mind a 'partial' re-mastering, which would just be updating
    just one read-only persistence squash file.

    Take Knoppix 7.7 for example. Klaus uses three cloops for his stuff:
    KNOPPIX aka KNOPPIX0 is a full 4 Gb cloop of Knoppix DVD material;
    KNOPPIX1 is a small 'overflow' cloop which currently has only a few
    3d-oriented programs; and
    KNOPPIX2, a really small cloop, just for proprietary flash for the CeBIT crowd.

    I would co-opt the 7.7 KNOPPIX2 cloop as my read-only persistence receptacle,
    doing a re-master with current & future new read-write persistence
    whenever I chose to commit newer r/w persistencee stuff to r/o.

    Re-mastering just KNOPPIX2 with r/w persistence material would take up
    much less real estate to accomplish and the final result would certainly
    be more efficient than strictly r/w persistence alone. I would sacrifice
    the capability to remaster to delete material, but all-r/w persistence
    already does that. I expect my 16 Gb Cruzer LiveUSBs would have room
    to spare doing such a 'partial' re-master.

    As a second act, I am fascinated by the idea that re-mastering might
    be achieved by working with squashed material rather than unsquashed
    material which mergeusb purports to do.

    atb

  3. #13
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    If you never do any huge upgrade or purge, working with incremental changes in overlays is IMHO perfectly fine. But you'll soon get something that takes up more space than necessary, and with a full 4GB squashing taking just a few minutes (3-10 for example), I don't really understand people being so afraid of it. In particular when it can be performed as a background process, as in this case - you don't need to notice it much. You just issue the command ramdisk_commit & in a terminal and continue with whatever you were doing. Also, the image and persistence handling is taken care of by minirt init.

    If mergeusb really works with squashed material all along, it will surely be possible to do the same. But I didn't get that impression. Everything just goes so fast when you are working with small images.

    And I'm still curious as to what forces you to use 16GB sticks in 2016..

  4. #14
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    Resquashing may surely take quite a bit more time with slow sticks - but, then, a small 120GB SSD costs about $50, and yesterday I did full Knoppix remastering in a kvm VM on a 5 year old i5 laptop, using an external SSD drive for copying - still < 30 min, and much of the time and space was used for creating isofs for the new cloop.

  5. #15
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    Quote Originally Posted by Capricorny View Post
    I don't really understand people being so afraid of...(remastering, in essence).
    Looking at mergeusb bash, I interpret that it loop mounts two squash files,
    one ro and one rw initially, and uses overlayfs to produce a merged file
    which it then squashes as a candidate new ro file, then proceeds to reformat
    the now empty rw file. This all takes place on a temporary directory which
    is erased on completion. It does not appear to me on closer inspection
    that the magic is accomplished at the squashed level after all. The main
    difference being that squash files replace cloops and overlayfs replaces aufs.

    This sure sounds like plain old re-mastering to me. At some point in the process,
    there has to be at least temporary storage for a complete un-squashed
    replica of the squashed material, in addition to all the squashed material,
    plus a complete ram-disk operating system.

    It is not fear which repulses me from this situation, it is the mindlessly
    uneconomic use of resources. Bloat is repulsive to me. Two Gb is enough
    resource to accomplish a generous allotment of applications and enough
    persistence to satisfy my additions and tweaks. My 16 Gb USB3 Cruzers cost
    $7. I don't know if you can even buy 2 Gb SanDisk SDHCs anymore, but 2 Gb
    is enough for my computing needs. With 14.48 Gb net to start with, GParted
    says my 7.7 Cruzer still has 9.74 Gb unused. I'd go for some scheme that
    could work some magic with that unused 9.74 Gb.

    Having five Gb devoted to Knoppix's read-only part also repels me, since
    I know it can be done in CD size, but I we haven't found an alternative
    distribution which has Klaus K's magic sauce, so I tolerate its obesity.
    Klaus does provide almost half-a-dozen unused cloop assignments, which he
    himself is now using with an atrocious lack of economy. One whole cloop
    for flash staggers my feeling for economic use of resources.

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