Hi,

Have checked my scripts quite thoroughly and run the exact following
without doing anything to the filesystems  except rebooting (yes I
created a /somewhere and /new dir just to double check!):

cd /usr/local/uml/test/
./linux ubda=/somewhere/root_fs_cow,/somewhere/root_fs stderr=1 con=null 
con0=fd:0,fd:1 con1=xterm mem=128MB umlid=myuml

mv /somewhere/root_fs /new/root_fs

./linux ubda=/somewhere/root_fs_cow,/new/root_fs stderr=1 con=null 
con0=fd:0,fd:1 con1=xterm mem=128MB umlid=myuml

same error for second invocation:
------------8<--------------------------
Couldn't stat '/somewhere/root_fs', err = 2
Couldn't stat "/somewhere/root_fs" : err = 2
Failed to get modification time of backing file "/somewhere/root_fs", err = 2
Failed to open '/somewhere/root_fs_cow', errno = 2
VFS: Cannot open root device "98:0" or unknown-block(98,0)
------------8<--------------------------
As you say "What's this?". The /somewhere/root_fs_cow definitely
exists. Just moving the root_fs back (mv /new/rootfs /somewhere)
and it is fine so I guess it is nothing broken its just the UML will
not allow rewriting the COW header?

Any clue where to look for this problem? I guess it must be possible
for me to write some suitable "printf" in some part of the kernel
where the check is made.... 

Also another Q: the "umlid" argument seems to be ignored (wherever I
put it in the argument list) as I just get some random characters for
the socket name, although they do work. Am I using the umlid correctly?

BTW: UML is very cool. I am about to deploy 3 UMLS on 80 student lab
machines so they can do some security tool experiments (hack into the
machines, learn to spot a rootkit and learn how to fix them, use SNORT,
iptables between them etc....). This kind of activity is very difficult to
achieve on multiple machines for large student numbers. I am building
a "uml_manager" in Tcl to start/stop/save COW snapshots etc, does
anyone else know of tools like this?

Regards,

Martin

Blaisorblade writes (edited with a few answers to Qs):
 > On Saturday 24 September 2005 20:12, [EMAIL PROTECTED] wrote:
 > > Hi,
 > 
 > > I cannot successfully move the backing file of a COW file. I am
 > > following the instructions for moving the backing file given at:
-edited-

 > This is what you complain about, but

 > > Failed to get modification time of backing file
 > > "/somewhere/root_fs", err = 2 Failed to open
 > > '/somewhere/root_fs_cow', errno = 2

 > What's this? It doesn't even find the COW file. Would you please
 > double check your configuration (say a startup script broken by the
 > move or anyway some other change)?

Checked all permissions etc no obvious problems, no change to the
system except for a reboot so nothing should be broken

 > Btw:
 > > usermode-utilities-20040406
 > Hope that's the -r1 Gentoo release (which contains a local DoS
 > security fix - an unprivileged user could easily bring down an
 > interface).
Sure is, but thanks for the warning.

Martin
--
Dr. M.J. Reed                               Room:          1NW.5.3G
Dept. Electronic Systems Engineering         Tel:+44 (0)1206 872479
University of Essex, Colchester CO4 3SQ, UK  FAX:+44 (0)1206 872900
Email mjreed (non Essex users should add @essex.ac.uk)
Web: http://esewww.essex.ac.uk/~mjreed


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