(13-11-2021, 04:56 AM)venam Wrote: Similarly, in the shell, arrow up doesn't show the previous command but
scrolls up. Obviously, there's no tab completion either.
Overall, I'll still need a while to get used to the UI.

9front has a " command that prints the previous command, and a "" that runs it. File completion is done with Ctrl+F.

(13-11-2021, 04:56 AM)venam Wrote: However, it quickly follows with analysis of processes exec layout and
virtual memory. I'm not so sure it's a good logical order, it felt
parachuted for me. At least, if I was writing for beginner students,
I would be surprised if they didn't nag when studying with such
book.

The book was written for the students of the Operating System courses the author is professor of. Since the course is given after the Computer Architecture course, the students should knew about virtual memory beforehand.

(13-11-2021, 06:22 AM)josuah Wrote: The group-based permission system is interesting, and solves the "shared directory" problem, which is a very common one: have one directory in read-write access by anyone in the group.

UNIX has that. Quoting from the APUE book, third edition, section 4.6:

Quote:The user ID of a new file is set to the effective user ID of the process. POSIX.1 allows an implementation to choose one of the following options to determine the group ID of a new file:
1. The group ID of a new file can be the effective group ID of the process.
2. The group ID of a new file can be the group ID of the directory in which the file is being created.

FreeBSD 8.0 and Mac OS X 10.6.8 always copy the new file's group ID from the directory. Several Linux file systems allow the choice between the two options to be selected using a mount(1) command option. The default behavior for Linux 3.2.0 and Solaris 10 is to determine the group ID of a new file depending on whether the set-group-ID bit is set for the directory which the file is created. If this bit is set, the new file's group ID is copied from the directory; otherwise, the new file's group ID is set to the effective group ID of the process.

Using the second option (inheriting the directory's group ID) assures us that all files and directories created in that directory will have the same group ID as the directory. This group ownership of files and directories will then propagate down the hierarchy from that point. This is used in the Linux directory /var/mail, for example.

Edit: More information on that in this Wikipedia article