File level recovery of Linux assets from incremental backups may fail

SUMMARY

File level recovery of Linux assets from incremental backups may fail.when files contain hardlinks

ISSUE

File level recovery of Linux assets from incremental backups may fail, though recovery from the full backup is typically successful. This issue has primarily been observed in CentOS 5 but may also be encountered under CentOS 6 appliances, and is related to how hardlinks in a Linux OS may be cataloged and recovered.  

RESOLUTION

To resolve this issue, upgrade to release 10.1. 

The last release for CentOS 5 based appliances was 9.1.1.  If your appliance is still on CentOS 5, it will require upgrading the OS if possible or replacement with a CentOS 6 system first. CentOS 5 was depreciated by Unitrends on Aug 31, 2017 and customers were asked to complete their migration to CentOS 6 between Feb 2015 and Aug 2016.  You may contact Unitrends Support to see if your appliance may still be able to upgrade to CentOS 6 even past this deadline.  

CAUSE

The issue related is with hardlinks associated to the file failing to recover when the original file is modified in an incremental and the newer version of the hardlinked original file is recovered prior to the linked object which may be from a different backup version. This can occur if rsync or other tool moved one or both ends of the link between 2 backups.  We have adapted code to handle this very rare scenario successfully.  

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