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    Require a bit less free memory before checking for upgrades. · 60ee6e88
    Tails developers authored
    The general goal is to avoid displaying "Not enough memory available to check
    for upgrades" too often due to over-cautious memory requirements checked in
    the wrapper.
    
    The specific goal is to avoid having to bump the hardware requirements for
    Tails 1.1 (Wheezy) to >> 1 GiB of RAM, as this would 1. not be very nice for
    users of oldish hardware; and 2. force us to implement #5502 ("Notify user if
    hardware requirements are not met") in time for the 1.1 freeze.
    
    My experiments, documented on #5390, indicate that even lower limits would
    probably work. Let's not be too adventurous to start with, though: my plan is to
    lower the limit to something that is low enough for the wrapper to dare running
    the check for upgrades, but still quite cautious.
    
    Later on, we could try lowering the limits even more, or even drop it entirely:
    this would require a mechanism to detect when the check for upgrades fails due
    to memory exhaustion, which don't have yet.
    
    Note that, if an automatic upgrade is available, Tails Upgrader checks memory
    again, to ensure there's enough free memory to apply the upgrade. This commit
    assumes that Tails Upgrader's own check is cautious enough, and that we were not
    implicitly relying on the check done earlier, in the wrapper, to ensure upgrade
    safety. This assumption might be wrong. My plan is to use the incremental
    upgrade to 1.1~rc1 as a test bench to verify this, as I have no time to fully
    test this fully right now (still, I successfully applied a small — 50 MiB —
    IUK on top of a current build from this very branch, with 126 MiB of free
    memory, and 700 MiB total free memory).
    
    The symptom of a failed upgrade due to lack of memory (and then, of a too low
    $mem_factor value in Frontend.pm) would be to see the upgrader that simply die
    in the middle of the download, or (worse) in the middle of the upgrade. In the
    worst case, the resulting (partially upgraded) system may not boot anymore, but
    no user data will be affected, and the user can still fix their stick by doing
    a full upgrade.
    60ee6e88
tails-upgrade-frontend-wrapper 1.85 KB