Lab 13.1: swapon on ubuntu 14.04 didn't say anything about "recommended" perms

Different Linux distributions have different tastes. 600 means only root can read/write to it which makes sense. apparently ubuntu doesn't care, although it should.

There are other examples; some distros are finicky about permissions of /etc/sudoers and files in /etc/sudoers.d . Just the way things are. 600 is a good practice whether
Ubuntu cares or not.

In practice, most systems use a swap device or partition, as it is less prone to
corruption if you have filesystem problems for example, and is also likely to
be contiguous in extent. Furthermore, on SCSI systems it is faster to spread
I/O on separate "spindles" (disks) as they can proceed in parallel, so putting
swap on a different disk is useful. I tend to put a swap partition on an old
fashioned rotational hard drive, while using faster SSD for most of active I/O.