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

[Ivan Porro <pivan@xxxxxxxxxxxxx>]

Hi all,

I'm new to the list so I actually doesn't know if my question is so 
dumb/RTFM  that no one is in charge of answering it or...something else 
(I'm not used to fire messages to lists as soon as a problem appears and 
this time I'm going really crazy).
My question is still there, however, the more I go deeper in the 
problem, the more situation appear to be clear:
Known that Xen require udev.
Known that SLC3/RHEL3 and so on use DevFs and not udev
Known that my domU without the line

ramdisk="/boot/initrd-2.6-xen.img"

obviously can't boot to a console but has all of the right permissions 
in /dev/ in place (maintenance consoel)...
I've recompiled xen from source, both using only one -xen kernel and 
both using -xenU / xen0 kernels.
I've tried to "enable" devfs in domU kernel but there are no option 
there for that. Browsing mailing list didn't helped, 'cause it seems to 
me that major revision had been in place form 2.6.12 since 2.6.16 kernels:
Is it correct? What I am missing which is so evident to all but not to 
me? Is it possible to run a devfs based distro with hypervisor kernel 
2.6.16 (xen 3.0.2)? If I look at kernel config files:
# config-2.6.12.6-xen3_12.1_rhel4.1
# Pseudo filesystems
#
CONFIG_PROC_FS=y
CONFIG_PROC_KCORE=y
CONFIG_SYSFS=y
# CONFIG_DEVFS_FS is not set
CONFIG_DEVPTS_FS_XATTR=y
CONFIG_DEVPTS_FS_SECURITY=y
CONFIG_TMPFS=y
CONFIG_TMPFS_XATTR=y
CONFIG_TMPFS_SECURITY=y
# CONFIG_HUGETLBFS is not set
# CONFIG_HUGETLB_PAGE is not set
CONFIG_RAMFS=y


# config-2.6.16-xen3_86.1_rhel4.1
# Pseudo filesystems
#
CONFIG_PROC_FS=y
CONFIG_PROC_KCORE=y
CONFIG_SYSFS=y
CONFIG_TMPFS=y
# CONFIG_HUGETLB_PAGE is not set
CONFIG_RAMFS=y
CONFIG_RELAYFS_FS=m
CONFIG_CONFIGFS_FS=m


hope some one can help or say me I'm an idiot so I can stop trying the 
impossible ;)
thanks in advance,
 ivan


Ivan Porro wrote:
> 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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