John Goerzen <jgoerzen <at> complete.org> writes:
>
http://backuppc.sourceforge.net/faq/limitations.html#incremental_backups_might_not_be_accurate
> there is documented a limitation of BackupPC incrementals with tar:
> since it uses timestamps only, it may miss if someone does something
> like unpack a ZIP file that contains files with timestamps in the past.
> It also won't note if files were deleted.
I'm beginning to think that the documentation here is wrong. I will do some
testing tomorrow. I think it is right regarding the deleted files, but wrong
regarding things like recently-unpacked ZIP files with timestamps in the past.
GNU tar's manual says that --newer looks at "files whose data modification or
status change times are newer than the DATE given". In other words, it examines
both mtime and ctime. If my understanding is correct, when something like an
old ZIP file is unpacked, unzip will set the mtime, but in so doing forces the
ctime to be updated to the current time. Therefore, assuming clocks are not
wildly out of sync, this should pose no problem. Right?
I will run some tests to validate this assumption tomorrow.
If it pans out, then it may just make sense for me to use tar instead of rsync
for all local hosts. The deleted files issue is not particularly critical for
me. I am then just left with the bug that doesn't let me restore, using the
CGI, from a backup made on a machine using tar to a machine using rsync. I ran
into the problem at
http://news.gmane.org/find-root.php?group=gmane.comp.sysutils.backup.backuppc.general&article=23890
which sadly had no responses.
-- John
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