Erik Sjölund's questions

I tried to convert a VMDK image found in a OVA file to the QCOW2 format with the qemu-img command but it failed with the error message qemu-img: error while reading sector 131072: Invalid argument

user@ubuntu:/tmp$ wget ftp://ftp.sanger.ac.uk/pub/databases/Pfam/vm/PfamWeb_20120124.ova
user@ubuntu:/tmp$ tar xfv PfamWeb_20120124.ova
PfamWeb_20120124_2.ovf
PfamWeb_20120124_2.mf
PfamWeb_20120124_2-disk1.vmdk
user@ubuntu:/tmp$ qemu-img convert -O qcow2 PfamWeb_20120124_2-disk1.vmdk PfamWeb_20120124_2.qcow2
qemu-img: error while reading sector 131072: Invalid argument
user@ubuntu:/tmp$ qemu-img --version | grep "qemu-img version" 
qemu-img version 1.0, Copyright (c) 2004-2008 Fabrice Bellard
user@ubuntu:/tmp$ dpkg-query -f='${Version}\n' --show  qemu-utils
1.0+noroms-0ubuntu14.1
user@ubuntu:/tmp$ cat /etc/issue
Ubuntu 12.04.1 LTS \n \l

How do I avoid the error?

The AFS volume quota is almost exceeded for one of our computer users. Running fs listquota or fs lq gives him a warning:

olifri@ubuntu:~$ fs listquota ~
Volume Name                    Quota       Used %Used   Partition
H.olifri                      500000     492787   99%<<       38% <<WARNING

I would like to share with him a shell script that would detect which of his directories consume most of his AFS volume quota. He would then have a better idea of where to start deleting files.

Note that in the AFS filesystem a user can mount other AFS volumes inside an AFS volume. This means that a recursion with /usr/bin/find might enter other AFS volumes that we are not interested in.

Our AFS client software is Openafs 1.6.1 and it runs on Ubuntu 12.04 computers. We have no admin rights on the AFS file servers as they are administrated by another department.

The command /usr/bin/du seems to be unaware of the concept of AFS volumes. The best idea I have right now is to write a script that for each subdirectory will test if the directory is a mount point for an AFS volume. For instance the command fs lsmount could be used for that. For a normal directory fs lsmount produces this result

esjolund@ubuntu:~$ mkdir ~/testdir
esjolund@ubuntu:~$ fs lsmount ~/testdir
'/afs/pdc.kth.se/home/e/esjolund/testdir' is not a mount point.

and for an AFS mount point fs lsmount produces this result

esjolund@ubuntu:~$ fs mkmount -dir ~/testmount -vol prj.sbc.esjolund00
esjolund@ubuntu:~$ fs lsmount ~/testmount
'/afs/pdc.kth.se/home/e/esjolund/testmount' is a mount point for volume '#prj.sbc.esjolund00'

Before starting to write the shell script, I would like to hear if you have any better ideas of how to solve the problem?

Is it allowed in DNS to have a CNAME record that points to another CNAME record?

The reason we need this is that we have a hostname that we want to be looked up to the IP address of our web server computer. We also have another web server computer stand by that could be activated in case the first one would die. In such a case we would quickly need to point the hostname to the IP address of the stand by web server computer.

Unfortunately the hostname resides in a DNS domain where any change would take long time due to manual operation dependent on other sysadmins. But we have another DNS domain where we can perform the changes ourselves quickly. Having CNAME to CNAME chain seems like a possible solution. But is it allowed? Will web browsers understand it?

I have a 64-bit CentOS 6.0 Linux computer with an Areca 1880i RAID card. The RAID card has its own ethernet port but it is right now not connected to anything. Instead of using that ethernet port for email notifications, I would like to send the email notifications from an ethernet port on the motherboard. I suppose that connecting the ethernet port on the RAID card directly to the internet is a bad idea security-wise because it runs its own firmware-based web server.

On this Areca web page:

http://www.areca.com.tw/support/s_linux/linux.htm

there is download link to the archttp software

http://www.areca.us/support/s_linux/http/x86_64/archttp64.zip

[root@server ~]# wget --quiet http://www.areca.us/support/s_linux/http/x86_64/archttp64.zip
[root@server ~]# unzip archttp64.zip 
Archive:  archttp64.zip
  inflating: archttp64       
[root@server ~]# chmod 755 archttp64 
[root@server ~]# ./archttp64  -h
Usage:

archttp32 [TCP Port#]
To Terminate the archttp: Press CTRL-C 
Command for reconfiguring the archttp: kill -sHUP <archttp's pid>
[root@server ~]# 

Here I notice that an empty configuration file was created when I ran ./archttp64 -h

[root@server ~]#  ls -l archttpsrv.conf 
-rw-r--r-- 1 root root 0 2011-08-25 15:56 archttpsrv.conf

I managed to start the web server software

[root@server ~]# ./archttp64 80
Copyright (c) 2004-2009 Areca, Inc. All Rights Reserved.
Areca HTTP proxy server, Version: V1.84, Arclib: 290, Date: Nov  2 2009

Starting HTTP Proxy Server...Please wait(MAX = 5 minutes)
Controller(s) list
-------------------------------------------------------
Controller[1](PCI) : Listen to port[80].
Cfg Assistant : Listen to port[81].
Binding IP: [0.0.0.0]
Note: IP[0.0.0.0] stands for any ip bound to this host.
-------------------------------------------------------

##############################
Press CTRL-C to exit program!!
##############################

I then accessed the web interface provided by archttp64 from my desktop computer by first creating a ssh tunnel

[user@desktop ~]$ ssh -N -L 8080:localhost:80 [email protected]

and then open the URL http://localhost:8080 in a Chromium web browser.

In the web interface I configured the fields for SMTP server and email addresses and chose Information notification as the event level, but no email was sent when I clicked Generate Test Event in the web interface.

How can I get the email notifications to work?

I created a KVM guest from the command line with virt-install where I used the command line options --disk pool=vg0,size=20 and --name virt1.example.com.

How can I delete this KVM guest from the command line? I don't need it anymore.

Just for the record the whole command line was

virt-install --debug --hvm --vnc --name virt1.example.com --os-type=linux --os-variant=rhel6 --pxe --network network=default,model=e1000,mac=02:54:00:13:be:e4 --disk pool=vg0,size=20 --ram 1024 --vcpus=1 

and here is some extra information

[root@server ~]# virsh vol-list vg0
Name                 Path                                    
-----------------------------------------
lv0                  /dev/vg0/lv0                            
lv_swap              /dev/vg0/lv_swap                        
virt1.example.com.img /dev/vg0/virt1.example.com.img  

[root@server ~]# virsh list
 Id Name                 State
----------------------------------
  3 virt1.example.com running

Update

Running these three commands seems to remove the installed KVM

virsh destroy virt1.example.com
virsh undefine virt1.example.com
virsh vol-delete --pool vg0 virt1.example.com.img

For more details see the terminal session:

[root@server ~]# virsh list --all
 Id Name                 State
----------------------------------
 3 virt1.example.com running

[root@server ~]# virsh undefine virt1.example.com
error: Failed to undefine domain virt1.example.com
error: Requested operation is not valid: cannot delete active domain

[root@server ~]# virsh destroy virt1.example.com
Domain virt1.example.com destroyed

[root@server ~]# virsh list --all
 Id Name                 State
----------------------------------
  - virt1.example.com shut off

[root@server ~]# virsh undefine virt1.example.com
Domain virt1.example.com has been undefined

[root@server ~]# virsh list --all
 Id Name                 State
----------------------------------

[root@server ~]# virsh vol-list --pool vg0
Name                 Path                                    
-----------------------------------------
lv0                  /dev/vg0/lv0                            
lv_swap              /dev/vg0/lv_swap                        
virt1.example.com.img /dev/vg0/virt1.example.com.img  

[root@server ~]# virsh vol-delete --pool vg0 virt1.example.com.img
Vol virt1.example.com.img deleted

[root@server ~]# virsh vol-list --pool vg0
Name                 Path                                    
-----------------------------------------
lv0                  /dev/vg0/lv0                            
lv_swap              /dev/vg0/lv_swap                        

[root@server ~]# cat /etc/issue
CentOS Linux release 6.0 (Final)
Kernel \r on an \m

[root@server ~]# virsh --version
0.8.1

How do I generate a random MAC address from the Linux command line?

I search for a solution that only requires standard tools commonly found on the Linux command line.

The MAC address will be used for a guest KVM.

The host server (running CentOS 6.0) only has one public IP address and will be hosting many KVM guests so it needs to use a virtual network switch configuration in NAT mode.

I have previously used pxelinux for automated installation of physical machines and would like to continue to use pxelinux for installation of KVM-guests. The reason for this is that I already have written some scripts that generate pxelinux configuration files and I would like to reuse them.

Could someone provide a step-by-step instruction of how to install a CentOS 6.0 KVM guest on a CentOS 6.0 host server?

I would like to use the command line as much as possible so I prefer virt-install to virt-manager.

The host server has only one LVM volume group: vg0

[root@server ~]# vgs
  VG   #PV #LV #SN Attr   VSize VFree 
  vg0    1   3   0 wz--n- 8.18t 97.90g

I have a server with this hardware

• two Intel Xeon E5620 CPUs
• Areca 1880i 8-port SAS RAID PCIe 512MB cache
• Areca Battery Backup Module
• 5 pcs Hitachi Deskstar 7K3000 HDS723030ALA640 64MB 3TB

and have created one RAID 6 volume that makes use of all the 5 hard drives.

Unfortunately there is no support for the Areca 1880i RAID card in the Linux kernel on the CentOS 6.0 installation image. There is though an updated kernel module available on the Areca web site (both as a precompiled binary for RHEL 6.0 and as source code).

How do I write a kickstart script to automate the installation of CentOS 6.0 on the server?

Update: Good news! CentOS 6.2 has support for Areca 1880i. When I upgraded to CentOS 6.2 by doing "yum -y update", the new kernel had native support for Areca 1880i. I haven't tested a CentOS 6.2 kickstart installation though, but I guess that should work too.

During a kickstart installation (Centos 6.0) of a server having this hardware:

• Areca 1880i 8-port SAS RAID PCIe 512MB cache
• Areca Battery Backup Module
• 6 Hitachi Deskstar 7K3000 HDS723030ALA640 64MB 3TB

I pressed ctrl+alt+del because I wanted to restart the kickstart installation. Restarting the kickstart installation in this way had worked before so I was surprised that the initialization of the Areca 1880i card failed at the next boot startup. First the computer showed this message for a few seconds

AMIBIOS(C)2009 American Megatrends, Inc.
Supermicro X8DTN+-F BIOS Date: 03/17/11 16:42:32 Ver 2.1
CPU : Intel(R) Xeon(R) CPU           E5620  @ 2.40GHz
 Speed : 2.40 GHz    Count : 2

Press DEL to run Setup (F4 on Remote Keyboard)
Press F12 if you want to boot from the network
Press F11 for BBS POPUP  (F3 on Remote Keyboard)

Initializing IPMI module, please wait. Done

Initializing USB Controllers .. Done.
System Fan Control function has been enabled, FAN#1,2,3 will be monitored.

Then it showed

Waiting for F/W to become ready. 003/300 seconds elapsed..

where the time counter was incremented up each second. After 300 seconds a short message stated that it had timed out and after that a new reboot started.

Trying to solve the problem I unplugged the 2 power cables (the computer has 2 PSU) and plugged them in again. That didn't help as the computer timed out once again with the same message when I started it again.

How can I fix this?