Backups on non-trusted FTP servers - The H Security: News and Features

FTP bugs

duplicity has well known problems with FTP servers that provide error code 550 when listing empty directories. You can recognise this if the following error message

duplicity.backends.BackendException: 550 *: No such file or directory.

appears during the first backup attempt. One solution in that case is creating an arbitrary (or even empty) file in the backup directory on the FTP server.

Peace of mind

Individual files can be restored from the backup using ftplicity fetch. The command requires three options: file and directory name, target, and age:

ftplicity fetch etc/passwd /root/pw 4D

That example command will restore /etc/passwd in the state from 4 days prior into /root/pw; "now" provides the current state. Details on the time format to be used can be found in duplicity's man page in the TIME FORMATS section.

In the event of a catastrophe, you should first boot your server using the provider's recovery system, then install the ftplicity script and restore the backed-up configuration directory into /root/.ftplicity. ftplicity automatically imports the GPG key stored there. Arrange for the desired partitioning of the hard drive and then start by mounting the new, freshly formatted root partition under /mnt. All further mount points should then be created there and the intended partitions should be mounted there. Keep in mind that you need to set the correct access rights for the tmp directory (chmod 1777 /mnt/tmp) and create the mount points for virtual file systems that were excluded from the backup, generally /dev, /proc and /sys. If your system does not use devfs, then you need to recreate the device files into /mnt/dev as per your distribution's documentation. ftplicity restore /mnt then completely recreates the backup in its last state on the new hard drive. Following restoration of the boot loader, your server will be the same as before. (cr)