Re: is dpkg install atomic?
On Tue 26 Oct 2021 at 13:57:13 -0400, Roberto C. Sánchez wrote:
> On Tue, Oct 26, 2021 at 10:31:54AM -0700, Han wrote:
> > Hi,
> > This might be a dumb question: is dpkg installing (or updating) a package
> > using a .deb file atomic in the event of power outage?
> > By atomic, I meant either the new version of the application is fully
> > installed, or not at all. Is this always guaranteed?
> > I read the `man dpkg` doc, but couldn't find a clear answer. I might have
> > missed it though.
> > Thanks,
> > Han
>
> It's not a dumb question. The installation of a package might seem,
> from the user perspective, like it could be atomic, but it is really
> made up of a variety of steps.
Indeed.
> Broadly, the package is downloaded, then unpacked, then any included
> pre-installation script is executed, the unpacked contents are placed in
> their location on the system, and then any included post-installation
> script is executed. A power outage at any point in the process could
> leave the package in a state where is it is not fully installed.
> Though, generally speaking, a situation like that can almost always be
> recovered from by a command like 'apt-get install --reinstall <pkg>'.
> However, there might circumstances where more advanced techniques might
> be required.
Assuming that Ctrl-C while dpkg or apt is running is equivalent to a
power outage, I have found that running the specific command afterwards
is generally successful.
--
Brian.
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