[Xen-users] login, SSH, and other issues due to permission on /dev changed after reboot

[Ivan Porro <pivan@xxxxxxxxxxxxx>]

Hi all,

I've a small setup of Xen 3 with scientific linux cern 4.3 dom0 and 
scientific linux cern 3.06 and 4.3 on few domUs
Kernel used is 2.6.16-xen3_86.1_rhel4.1.   I've domU images on files on 
a partition of dom0. This partition is also exported with NFS (another 
dom0 for domain migration is plannes, and if I'm not wrong,  the only 
option there is to have domU partitions stored on files)
Everything is apparently fine, except the problem of wrong permissions 
on /dev entries. This happens only on Scientifc Linux 3.06 (RHEL3) 
domUs. I've "upgraded" them to kernel26 following CERN instructions 
(http://linux.web.cern.ch/linux/scientific3/docs/kernel26.shtml) so 
modutils are ok. After some testing I've found
that devices are in place with wrong permissions.

I don't know if these are relate issues, but in the past I was not able 
to install an Oracle10 XE on a 3.0.6 domU and actually, an Apache 
1.3/PHP 5.1.2 server seems to crash randomly while connecting via Oracle 
instant client (OCI8 APIs) to a Oracle server.  I can only guess that my 
setups are influenced by a mad /dev configuration, so I'm trying to 
investigate that before going deep into application issues.
Wrong permission on /dev broke for sure other things, becuase SSH from 
domU to other hosts doesn't work (permissions on /dev/random and 
/dev/urandom, on /dev/zero... )
Making right permissions on /dev is off course a solution but after a 
reboot the permissions are wrong again:
# su - myuser
bash: /dev/null: Permission denied
...
[myuser]$

# chmod a+rw /dev/*
# su - myuser
[myuser]$

... reboot ...

# date
Thu Aug 24 11:33:01 CEST 2006
# ll /dev/null
crw-------    1 root     root       1,   3 Aug 24 11:32 /dev/null

my config file for domU is:

kernel = "/boot/vmlinuz-2.6-xen"
ramdisk="/boot/initrd-2.6-xen.img"
memory = 512
name   = "myhost"
extra  = "nousb selinux=0  3"
vif    = [ 'mac=00:16:3e:00:10:11, bridge=xenbr0' ]
disk   = ['file:/export/virtual_disks/myhost/root.img,hda1,w'
        ,'file:/export/virtual_disks/myhost/data.img,hda2,w'
        ,'file:/export/virtual_disks/myhost/swap.img,hda3,w'
        ]
root   = "/dev/hda1 ro"

fstab look like:

/dev/hda1                /                       ext3    defaults        1 1
/dev/hda2                /opt                       ext3    
defaults        1 1
none                    /proc                   proc    defaults        0 0
none                    /dev/shm                tmpfs   defaults        0 0
none                    /dev/pts                devpts  
gid=5,mode=620        0 0
/dev/sys                /sys                    sysfs   defaults        0 0
/dev/hda3         swap                    swap    defaults        0 0
dom0_IP_address:/scratch   /scratch                nfs     
rw              0 0
Mounted filesystems are apparently ok:

$ mount
/dev/hda1 on / type ext3 (rw)
none on /proc type proc (rw)
none on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/hda2 on /opt type ext3 (rw)
none on /dev/shm type tmpfs (rw)
/dev/sys on /sys type sysfs (rw)
dom0_IP_address:/scratch on /scratch type nfs (rw,addr=130.251.10.160)


Thank you in advance,

 Ivan



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