Suddenly, on Jan 6, 2001 between 06:28:14 GMT and 06:28:15 GMT (i.e. in only one second!) 236MB of /dos/d (which is totally 253MB in size => almost all of /dos/d !) changed its modification time! Look at the following output :
bacchus:~ # /bin/gtar --create --directory /dos/d --incremental --newer-mtime "2001-01-06 06:28:14 GMT" --sparse --one-file-system --ignore-failed-read --totals --file /dev/null . Total bytes written: 247214080 (236MB, 39MB/s) |
bacchus:~ # /bin/gtar --create --directory /dos/d --incremental --newer-mtime "2001-01-06 06:28:15 GMT" --sparse --one-file-system --ignore-failed-read --totals --file /dev/null . Total bytes written: 286720 (280kB, 93kB/s) |
Of course, AMANDA has correctly backed up a level 1 of 236+ MB...But why should this one filesystem change mtime almost as a whole in just one second? Probably, somehow the directory entry of /dos/d changed, causing tar to dump everything beneath it. But I could swear I didn't touch /dos/d...
Here are some words of caution from the tar info file:
*Please Note:* `--after-date=DATE' (`--newer=DATE', `-N DATE') and `--newer-mtime=DATE' should not be used for incremental backups. Some files (such as those in renamed directories) are not selected properly by these options.
I use the described solution for almost a year without having experienced any other surprises. It works for me. I hope it will work for you too.