Re: Is there still a point in installing libgcrypt to /lib instead of /usr/lib

[Wouter Verhelst <wouter@grep.be>]

[sorry for the late reply; catching up on email]

On Fri, Feb 21, 2020 at 04:23:15PM -0500, Anthony DeRobertis wrote:
> On 2/21/20 2:00 AM, Wouter Verhelst wrote:
> > Even so, if we want to do so, this can be done correctly by a preinst
> > script in new libc, by way of a script that does the following:
> > 
> > cp -a /lib/<dynamic linker name> /usr/lib/<dynamic linker name>
> > ln -sf /lib/<dynamic linker name> /usr/lib/<dynamic linker name>
> > 
> > The first of the above two creates the new file; the second replaces the
> > old file, atomically, by a symlink.
> 
> Errr, pretty sure you meant to have the ln arguments in the opposite order.
> The link name is the second argument to ln.

Yes. I keep messing that up in production (ln is one of those commands
that I continually need to read the man page of)

> Besides that, you need a sync after the cp. Otherwise (in the event of an
> ill-timed crash) the data may not be written out, and you might wind up with
> /usr/lib/<dynamic linker name> being, e.g., a zero-byte file (with
> /lib/<dynamic linker name> a symlink to it). Possibly you even end up with
> /usr/lib/<dynamic linker name> missing, and /lib/<dynamic linker name> a
> dangling link.

Good point, yes.

My point was mostly though that it's possible to implement this
atomically, not to write a bug free script ;-)

-- 
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