Backup disks from my Linux system turned out not to be
readable on Win10 systems.
They are external disks formatted as NTFS, then with a
VeraCrypt container file with an ext4 filesystem inside. I was able to decrypt the
container with VeraCrypt on Win10 to make local disk N: appear. But then neither
on Win10 would recognize the decrypted (ext4) volume presented by VeraCrypt.
Filed a bug report with Linux Reader, and within two days they had fixed the issue with their application !
Looks like I should use exFAT inside (and maybe outside too).
Linux kernel 5.4 is first version to officially support exFAT, with additional
support coming in 5.6 or 5.7. I'm using 5.4.
"sudo apt install exfat-fuse exfat-utils"
To change my backup drive to exFAT , I had to attach it to my Linux system,
copy the data to elsewhere (took an hour or more),
unmount the drive in file-explorer,
use GParted to make one big unformatted partition on the drive,
then use Ubuntu "Disks" (AKA gnome-disks) to format the partition to exFAT
(edit partition type to set to "NTFS/exFAT/HPFS (0x07)" and Format Partition to Type "Other" and then exFAT).
That went quickly. As usual the drive shows up as 1 TB raw and 931 GiB usable (which is 976 GB).
Copied some files (VeraCrypt apps for Win10 and Linux) to the partition.
Then I used VeraCrypt to make an encrypted container filling the rest
of the partition's space, formatted as exFAT (specified no files bigger than 4 GB,
portable to multiple OS's). That took over 12 hours !
Decided I was making things needlessly complex; started over.
Used GParted to leave the drive with no partitions at all.
Used VeraCrypt to make an encrypted volume (on the drive /dev/sdb,
not a partition /dev/sdb1), formatted as exFAT (specified no files bigger than 4 GB,
portable to multiple OS's). Able to select "Quick Format", which means it was
created in a matter of seconds. Mounted it through VeraCrypt.
Copied my backup data onto the drive, finding that some of my node.js development
libraries have symlinks in them, had to "skip all" those. Also ext4 allows chars ':"?*' in
filenames but exFAT doesn't, had to fix those.
And ext4 supports symlinks, exFAT doesn't.
Someone says exFAT doesn't support Linux file permissions, but I don't see how that could be.
("sudo blkid" is the best way to see what type a filesystem is. In output of blkid,
exFAT displays as 'SEC_TYPE="msdos" TYPE="vfat"'; NTFS displays as 'TYPE="ntfs" PTTYPE="dos"'.)
Also, in VeraCrypt click the
"Volume Tools ..." button and select "Backup Volume Header ..." and
save the backup to somewhere else, with a decent name.