note that in both cases, if you are aiming to make a snapshot that doesn't wind up with momentary changed files out of sync (like, browser cache/state data is likely to be mangled if it takes ages to get through it), better to remove the '|xz -9` and remove the `.xz` at the end on both and then `xz -9 src.tar` `xz -9 dotfiles.tar` to finish the job.