cloudware: purge pkg cache after installation

[zlei]

release/tools/vmimage.subr

144

# man 5 pkg.conf
...
     AUTOCLEAN: boolean
                      Automatically cleanout the content of PKG_CACHEDIR after
                      each non dry-run call to pkg-install(8) or
                      pkg-upgrade(8).

A cleanout on each iteration looks heavy-weighted.

Shall we batch installing and finally do the cleaning out ? i.e.,

/usr/sbin/pkg install -y ${p1} ${p2} ${p3} ...

[dch]

release/tools/vmimage.subr

144

in what way is this "heavy", in context of the overall build?

The intent is to reduce as much as possible overall image size,
as even the temporary writes use blocks that aren't truly freed,
from the perspective of a compressed raw image format.

The ever-increasing python install for cloudinit images makes a
big impact.

I would actually prefer to mount a tmpfs in /var/cache/pkg, or
move the pkg dir out completely during the install to avoid this
entirely, but I don't think that's possible.

[zlei]

release/tools/vmimage.subr

144

Sorry, for "heavy" I meant /usr/sbin/pkg install may re-download dependencies those are shared by packages.

I would actually prefer to mount a tmpfs in /var/cache/pkg, or
move the pkg dir out completely during the install to avoid this
entirely, but I don't think that's possible.

Why not ? I think nullfs can help.

[dch]

release/tools/vmimage.subr

144

I checked and it doesn't re-fetch dependencies its already installed.
I am not sure if the CLOUDWARE built images are always done as root.
If they are, we can use tmpfs overlay to avoid all writes, which is
even better. If not, this is better than the default.