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Re: [Xen-users] login, SSH, and other issues due to permission on /dev c

To: xen-users@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-users] login, SSH, and other issues due to permission on /dev changed after reboot
From: Ivan Porro <pivan@xxxxxxxxxxxxx>
Date: Fri, 25 Aug 2006 11:44:10 +0200
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Well, I answer to myswlf.

SLC3 is RHEL3, a 2.4 kernel based distribution, and use  devfs
SLC4 is RHEL4, a 2.6 kernel based distribution, and use  udev

Now the question is: what is the better solution?

a) unique kernel compiled by hand with both udev/devfs support
b) two distinct dom0 and domU kernels
c) others ?

Is this a Xen 3.0.2  "problem" only?

thank you in advance,
ivan

Ivan Porro wrote:
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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