[pacman-dev] [RFC] adding a --sysroot option

[Allan McRae]

On 19/12/16 00:53, Andrew Gregory wrote:
> On 11/29/16 at 10:58am, Andrew Gregory wrote:
>> pacman's --root option is regularly (mis)used to use pacman to manage
>> a mounted guest system, typically one whose pacman installation is
>> currently broken.  We have a few configuration defaults in place to
>> make this sort of work, but support is incomplete.  Those defaults
>> only actually take effect if the settings haven't been set in
>> a configuration file, several options still default to the host system
>> resources, and using the guest's pacman configuration requires
>> updating all configured paths to the new mounted location.
>>
>> Adding a --sysroot/--chroot option would allow pacman to properly
>> operate in a mounted guest system.  At the moment, there are two ways
>> we could accomplish this:  prefix all paths with the sysroot or just
>> call chroot(2).  Obviously, the problem with chroot(2) is that it
>> requires special privileges.  Unfortunately, I think my symbolic
>> user/group patch (https://patchwork.archlinux.org/patch/3694/) will
>> require chroot to work properly as I can't find any other way to look
>> up users/groups in a mounted guest.  So, we may have to implement both
>> approaches so that regular users can perform queries but privileged
>> users can perform transactions with proper symbolic name support.
> 
> How should --sysroot handle user-provided paths on the command-line?
> Should they be treated as relative to --sysroot or the current root?
> Assuming that at some point this will be implemented using chroot(2)
> in at least some instances, all paths, including any package files
> given to -U, *must* exist under --sysroot.  So, even though I think
> interpreting paths relative to the current root is more intuitive, it
> means extra work for us to determine if the path is accessible under
> --sysroot.
> 

My opinion with --sysroot, is that everything should be relative to the
sysroot.   As far as I can tell, that would be consistent with chroot,
systemd-nspawn, etc.

A