[Libguestfs] Transform and "Lenses xx and xx could be used to load this file"

Hi David, We have a general problem using Augeas in libguestfs and I wonder if you have any advice. The problem is that we often -- as with yesterday's patch -- add new config file paths to lenses. Or we want to parse config files which are not necessarily in the exact paths that Augeas is expecting. Now it's easy enough to parse such files using an arbitrary lens by calling aug_transform, eg: $ ls passwd $ augtool -r `pwd` augtool> transform passwd incl /passwd augtool> load augtool> ls /files/passwd/ abrt/ lightdm/ rjones/ adm/ lirc/ root/ akmods/ lp/ rpc/ # etc As you can see I applied the 'passwd' lens to the /passwd file because it's not in the expected location (/etc/passwd). However if the Augeas lens happens to contain that path already, things go wrong: augtool> transform passwd incl /etc/passwd augtool> load # /etc/passwd is not parsed by the passwd lens augtool> get /augeas/files/etc/passwd/error/message /augeas/files/etc/passwd/error/message = Lenses @Passwd and passwd.lns could be used to load this file This is specifically a problem when libguestfs adds a call to aug_transform to cater for a file that is not covered by an existing lens, but then Augeas adds that file, and then we get the error above until libguestfs removes the call to aug_transform. We cannot control when Augeas and libguestfs are released in different Linux distros. There are workarounds for this involving fishing out the existing transform and working out if it covers the file or not, but that's pretty tedious. It seems to be that Augeas could be cleverer here and could just ignore the case where two identical transforms apply to the same file and DWIM. What do you think? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-top is 'top' for virtual machines. Tiny program with many powerful monitoring features, net stats, disk stats, logging, etc. http://people.redhat.com/~rjones/virt-top