Re: Poor Man's XT doc (pre-releace)
On Wed, Aug 19, 1998 at 06:48:37PM +1000, Brian May wrote:
> >>I am confused... How do you intend to run X as non-root? I think it
> >>might be better just to make mount the NFS partitions as read-only,
> >>for normal use.
> >
> >Normally you have an Xserver that's SUID root (or a SUID root wrapper for it)
> >so that regular users can run it and access the hardware (which currently
> >requires root access). This is not desired on an Xterm as all processes run
> >as root user.
> >If you have the NFS server setup as root_squash then the client computer (the
> >X server) will have read access to all files (give them all world-read
> >access) but no write access apart from /tmp. I believe that Stephen's latest
> >idea of exporting read-only and then using a RAM disk for /tmp is a better
> >idea though.
> >I wouldn't be inclined to skip the ext2 file system though. I believe that
> >ideally an X terminal will use kmod and have a whole range of modules
> >including sound drivers and drivers for all floppy disks. Basically IMHO you
> >want your X server to have drivers for every IO device you're likely to want
> >to connect to it.
>
> Does X allow sharing of floppy disks and audio?????
Thats a good question...and one of mine too
currently with my setup if I run a program that has audio it plays
on the host machine...kinda ugly...
(esp whgen the host is upstairs)
> >>The real problem I see, security wise, is that /etc cannot be read-only
> >>as it contains files that must be writable (I think), like /etc/mtab. This
> >>is really annoying. It also means that the root filesystem cannot
> >>be shared. The root filesystem must contain /etc, /bin, /sbin, so I seperate
> >>copy of all these files must be kept.
> >
> >AFAIK /etc does not need write access. /etc/mtab is not written if you use
> >the -n option of mount (you can have a pre-made version that says that
> >everything's mounted). This is a problem for umounting (there is no -n flag
> >for umount), but you don't REALLY need to umount an NFS partition -
> >especially a read-only one.
>
> Question: Why is /etc/mtab required? Why not just have a symlink
> from /etc/fstab to /proc/mounts? Although on my computer, the entry
> in /proc/mounts for the root partition looks wrong:
> /dev/root / ext2 rw 0 0
Well....
It isn't required...I didn't fool with mtab at ALL.
I mount the entirety of /etc read-only. In fact....I don't even bother
unmounting the read-only nfs partition...just shut the XTerminal off
>
> /etc requires write access in order to allow local-logins (I think),
> as libc6 creates a file called /etc/.pwd.lock (YUCK!). (I am not
> absolutely certain that this is still the case, however I did see
> a bug reported against libc6 that this file is never deleted).
Hmm good :) Local logons on an XTerminal are not only exteremely
discouraged but it was one of the goals of the project to make them
impossible. In fact... inittab was edited to run NO gettys
nor is inetd running. If you were to do a ps on the system
you would find quickly the ONLY programs running
(barring a few I missed) SHOUL Dbe init and the X Server
> >>Of course, it may be possible to remount /etc as another writable
> >>filesystem during boot, but this approach still makes me nervous (any
> >>changes made to /etc will come out as errors before /etc is re-mounted).
> >
> >I've been thinking of this. There are some files such as /etc/hostname which
> >need to be different. I was thinking of having them be sym-links to files
> >under /tmp and then generate the files on /tmp at boot time.
>
> I was thinking a good solution might be to mount a host specific
> configuration directory early during boot, eg in a file
> pointed to by a symlink /etc/rcS.d/S00*. This could do something like
> mount server:/etc/ip-address /etc/local, and
> have symlinks from files in /etc to /etc/local
>
> Note:
> 1. /etc/local could be mounted read-only,
> 2. As /etc/local is mounted early in the boot process, you could
> even have different versions of files like /etc/fstab for each
> computer (this could be important if the computers aren't dedicated
> to diskless Linux).
while that IS true...I think it is more than the XT project needs
> >>Otherwise, it might just be possible to mount the entire root filesystem
> >>as read-only except for /tmp and /var. I have heard of schemes where
> >>the /tmp partition is a local harddisk that is formatted on start-up,
> >>removing any long-term security implications. A seperate copy
> >>of /var would be required for each diskless computer.
> >
> >What do you need /var for? No mail, no squid cache, no logs needed...
>
> In my setup, I have a fully operational Linux computer via NFS-Root
> which requires log files, lock files, etc.
Well for a fully functional system yes :) you do need those.
-Steve
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