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--configure package...|-a|--pending
Reconfigure an unpacked package. If -a or --pending is given
instead of package, all unpacked but unconfigured packages are
configured.
Configuring consists of the following steps:
1. Unpack the conffiles, and at the same time back up the old
conffiles, so that they can be restored if something goes wrong.
2. Run postinst script, if provided by the package.