Before dropping a file, git-annex wants to be able to look at other remotes, and verify that they still have a file. After all, it could have been dropped from them too. If the remotes are not mounted/available, you'll see something like this.
# git annex drop important_file other.iso drop important_file (unsafe) Could only verify the existence of 0 out of 1 necessary copies Unable to access these remotes: usbdrive Try making some of these repositories available: 58d84e8a-d9ae-11df-a1aa-ab9aa8c00826 -- portable USB drive ca20064c-dbb5-11df-b2fe-002170d25c55 -- backup SATA drive (Use --force to override this check, or adjust numcopies.) failed drop other.iso (unsafe) Could only verify the existence of 0 out of 1 necessary copies No other repository is known to contain the file. (Use --force to override this check, or adjust numcopies.) failed
Here you might --force it to drop
important_file if you trust your backup.
other.iso looks to have never been copied to anywhere else, so if
it's something you want to hold onto, you'd need to transfer it to
some other repository before dropping it.