OK, post-mortem: 1. after reviewing everything, the best hypothesis I have is that the root of the problem was a bug in my backup script: it should have checked that the backup disk was properly mounted before proceeding with the back-up; something may have gone wrong with the mounting of XD after it was reformatted, but this failure went undetected; rsync just created the target directory under /media in HD.
2. it looks like photorec can find a fair bit of recoverable data from the first XD backup, but it's going to be a long slog to sort out the recovered files (400GB's worth); for most of this I have an older backup from 5 months ago; so the problem will be to identify the stuff added since then. I guess this is what learning Debian in the "school of hard knocks" is all about... This one knocked me out cold. kj On 3/12/16, Kynn Jones <kyn...@gmail.com> wrote: > I realize that my last e-mail included too little information. Sorry > about that. Here are some more relevant details. > > It turns out that I backed up the hard disk (HD) to the external drive > (XD) twice. The first backup went well, as far as I can tell. I > spot-checked individual files, etc. Everything looked normal. > > This first backup would have sufficed, but after I had done it I came > across the recommendation that a disk of that size (2TB) should be > formatted for ext4, whereas I had originally formatted it for ext2. I > reformatted the disk for ext4 (fdisk + mkfs.ext4), and then repeated > the backup. This backup procedure was in the form of a shell script, > that I had tested repeatedly. I just re-ran it. My memory is fuzzy > on the subsequent details. Since everything had gone so well up to > that point, I probably did not check everything as obsessively as I > had up to that point, but something must have gone very wrong. > > At any rate, at the moment, my only hopes are that > > 1. something may be recoverable from the first backup in XD; > 2. something may be recoverable from HD. > > The second of these is (I think) less likely, because I changed the > partition scheme for HD, going from a single partition, to separate > partitions for /, /var, /tmp, and swap. In contrast, XD has always > consisted of a single partition. > > Now I'm looking for some data recovery tool (preferably from Debian) > that either is part of some bootable media, or that I can use from a > USB stick after first booting from a Debian Live CD. > > Any recommendations for these would be appreciated. > > Many thanks in advance! > > kj >