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Re: Corel/Debian Linux Installer

Russell Coker <russell@coker.com.au> writes:

> Opening device files on a read-only file system works well for me.  I've just
> mounted a file system read-only, see this:
> rjc@lyta:/usr/src$touch foo
> touch: foo: Read-only file system
> rjc@lyta:/usr/src$ls -l null
> crw-rw-rw-   1 root     sys        1,   3 Aug  1  1997 null
> rjc@lyta:/usr/src$cat /etc/passwd > null
> rjc@lyta:/usr/src$
> Seems that read-only file systems only apply to real files.  I have only tested
> this with ReiserFS, but I believe that it's all VFS functionality and should

Can you give me a good point to look for docs about ReiserFS?

> work in all file systems.  If it doesn't then that's a kernel bug.
> /dev can be mounted read-only if you don't need/want to change permissions etc.

You are opening another device. The readonly only works for the one
device the filesystem is on. You can mount /home readwrite on a
readonly /. Same thing, just another name.

> For /etc, the fstab file is not a problem.  mtab could be an issue, but it
> could be a sym-link pointing elsewhere (so you re-mount root with the "-n"

Actually it could be removed. I allways wanted mount to use
/proc/mounts or the corresponding kernel call. /etc/mtab can only be
wrong and in case mounting / rw failed and you specified root=<dev>
different to the /etc/fstab entry, you actually have to remount the
wrong device to get the right device readwrite, because mount trusts
/etc/fstab more than the kernel.

> option).  If you use a service such as LDAP for authentication then you only
> need an entry for root in /etc/passwd (and probably other system accounts). 
> User accounts don't need it.  Of course changing the root password would be a
> real PITA!

As installing anything is (if you have /usr readonly also). But its
also a pain if /usr is mounted via net.

> >To append to another message I just sent, I also like /var being by itself
> >for logfiles.  In case all the other partitions fill you aren't left not
> >knowing what's happening (assuming of course you give yourself enough
> >size).
> Alternatively if a daemon goes into an infinite loop writing error messages
> (seen this happen with an old version of cfingerd and also with a commercial
> LDAP server) then you don't want it to remove all space from /home, /database,
> etc...

ypbind does that regulary on an old suse system here. When /var is
full, the system crashes, reboots, compresses the logfiles and goes on
again for a bit shorter. Every 3 Month it becomes critical, because
/var is so full with old logfiles that it gets hardly any uptime.

May the Source be with you.

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