Bug#982461: apt: Please provide a configuration option for disabling fsync()-s
On Wed, Feb 10, 2021 at 03:10:45PM +0100, Balint Reczey wrote:
> Source: apt
> Version:
> Severity: wishlist
>
> Hi,
>
> I run eatmydata apt ... frequently and it is used widely by others
> when there is no need to fsync()-s during package installations or
> removals, but it is nice to save time and wear off SSDs later.
>
> Using fsync() is unlikely to bring any benefit when a system is very
> unlikely to crash or it is cheap to recreate in case of an
> installation failure like it is the case for provisioning containers.
> Also using fsync is fairly pointless when apt-btrfs-snapshot is
> installed and a snapshot is taken after the apt operation anyway.
>
> Ideally dpkg would provide a command line option for skipping fsync,
> but it is not yet the case: #923423.
>
> On APT's side I'd like to propose a config option which when set would
> prefix dpkg calls with eatmydata until dpkg has a better interface for
> disabling fsyncs.
dpkg already has --force-unsafe-io to avoid syncs, it's what I use. I
don't want to have an option for eatmydata inside apt, it also affects a
lot of other stuff down the line like services outside on sysvinit
systems and all stuff happening in maintainer scripts; but then it only
works on the native architecture, not for foreign ones, and scripts
might be unsetting LD_PRELOAD. Heck APT probably should unset
LD_PRELOAD like it cleans up PATH.
I considered adding a seccomp filter to apt that would block fsync() and
friends, which is more persuasive than eatmydata. But force-unsafe-io is
usually enough.
Lastly, you can also just create a dpkg -> eatmydata symlink somewhere,
and then specify that as your Dir::Bin::dpkg, and that would work too.
eatmydata could ship some symlinks in /usr/libexec/eatmydata, similar to
what ccache does.
I do not believe that adding such a hack to apt is the right approach.
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