This allows us to find out all `live' packages on the system by
doing
nix closure $(cat /nix/var/nix/links/*.hash)
which will print out the activated configurations and all packages
referenced by them. We could then garbage collect unused packages
by deleting the difference between `nix listinst' and the set
returned by `nix closure ...'.
build action for `system' packages (like system.fix) that have
dependencies on all packages we want to activate.
So the command sequence to switch to a new activation configuration
of the system would be:
$ fix -i .../fixdescriptors/system.fix
...
system.fix -> 89cf4713b37cc66989304abeb9ea189f
$ nix-switch 89cf4713b37cc66989304abeb9ea189f
* A nix-profile.sh script that can be included in .bashrc.
