Autarchy of the Private Cave

Tiny bits of bioinformatics, [web-]programming etc

    Archive for December, 2016

    How to: enable metadata duplication on an existing btrfs filesystem

    30th December 2016

    Just one command: sudo btrfs balance start -v -mconvert=dup /toplevel/
    where /toplevel/ is your mountpoint of the btrfs root, -v is there for verbosity (not too verbose, don’t worry), and -mconvert=dup literally says act on metadata only, convert data profile to DUP.

    This will duplicate both metadata and btrfs system data.
    Verify with: sudo btrfs fi df /toplevel:

    Data, single: total=10.00GiB, used=3.88GiB
    System, DUP: total=64.00MiB, used=4.00KiB
    Metadata, DUP: total=512.00MiB, used=286.18MiB
    GlobalReserve, single: total=96.00MiB, used=0.00B

    Explanation: on SSDs, mkfs.btrfs creates metadata in single mode (because of widely spread SSD deduplication algorithms negating duplicate entries). However, second copy of metadata increases recovery chances, especially so if your SSD does not deduplicate writes. Hence the desire to add metadata/systemdata duplication after the filesystem is created.

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    Posted in *nix, how-to, Notepad, Software | No Comments »

    Raspberry Pi Colocation service

    29th December 2016

    Exactly what the title says: Raspberry Pi colocation service, yay! At only 30 EUR/year as of this writing.

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    Mail-in-a-box, Sovereign, Modoboa, iRedMail, etc

    28th December 2016

    Preparing to dismantle my physical server (and move different hosted things to one or more VPS),
    I’ve realized that an email server is necessary: to send website-generated emails, and also
    receive a few rare contact requests arriving at the websites.

    My current email server was configured eons ago, it works well,
    but I have no desire to painfully transfer all the configuration…
    Better install something new, shiny and exciting, right? :)

    I had 3 #self-hosted, #mail-server bookmarks:

    (Sovereign, the 4th one, was addded after reading more about Mail-in-a-box.)

    Here are my notes on what seemed important about these 4.
    Read the rest of this entry »

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    Posted in *nix, Comparison, Links, Notepad, Software, Web | 3 Comments »