I expect from that command no more and no less than what is explained in the man page:
Update (and list) only those files in the destination directory /backup which are older (less recent inode change or file modification times) than files with the same name found in the source file tree home: $ pax -r -w -v -Y -Z home /backup While that works as explained when copying to a ffs drive, running the same command again and again to a ext2fs target *all* files are copied again, even those already updated, what suggests me that pax(1) fails to get ext2fs timestamps right. But this is asking to much to OpenBSD, right? Linux don't even support ffs. That's why I didn't put much care in reporting this issue or sending it to bugs@. Besides, in general, to backup my files, I don't trust synchronizing files (for which I use rsync) to foreign file systems, in this case I save a *.tag.gz to the drive. By the way, currently I'm not using OpenBSD in any production system but in my desktop and just for fun. So, most of the time when I post something here I'm not asking for help but trying to contribute to the project. I appreciate your concern about my luck anyways. -- Walter Using my patched version of OpenBSD mail(1). https://en.roquesor.com/Downloads/mail_patches.tar.gz