# June 24, 2017: assertion when using rdiff-backup to backup a directory on an external hard drive

The error obtained is
  File "/usr/lib/python2.7/dist-packages/rdiff_backup/regress.py", line 233, in set_regress_inc
assert len(newer_incs) <= 1, "Too many recent increments"
AssertionError: Too many recent increments

It is difficult to find a solution on the web. See in particular here. I do not want to remove my backup and start a new one (almost 1 To to backup and many files: it is about one night long!), but I do not care in previous increment backups, only the previous one is enough. The solution is thus to do:
\$ rdiff-backup --remove-older-than 1s BACKUP_DIRECTORY

where BACKUP_DIRECTORY is the rdiff-backup directory root on the external hard drive. After that the assertion "Too many recent increments" disappears.