Cobbler reposync failed

I run daily cobbler reposync crons and it appears sometimes the process fails with the following error :

 Exception occured: <class 'cobbler.cexceptions.CX'>  
 Exception value: 'cobbler reposync failed'  
 Exception Info:  
  File "/usr/lib/python2.6/site-packages/cobbler/utils.py", line 126, in die  
   raise CX(msg)  
   
 Exception occured: <class 'cobbler.cexceptions.CX'>  
 Exception value: 'cobbler reposync failed'  
 Exception Info:  
  File "/usr/lib/python2.6/site-packages/cobbler/action_reposync.py", line 125, in run  
   self.sync(repo)  
   File "/usr/lib/python2.6/site-packages/cobbler/action_reposync.py", line 169, in sync  
   return self.yum_sync(repo)  
   File "/usr/lib/python2.6/site-packages/cobbler/action_reposync.py", line 402, in yum_sync  
   utils.die(self.logger,"cobbler reposync failed")  
   File "/usr/lib/python2.6/site-packages/cobbler/utils.py", line 134, in die  
   raise CX(msg)  
...
!!! TASK FAILED !!!

I don't really have an explanation for this but it seems that the reposync process doesn't really fail as if I run the reposync command manually the process goes fine.

The createrepo command line is shown when you execute "cobbler reposync", for example :

 hello, reposync  
 run, reposync, run!  
 creating: /var/www/cobbler/repo_mirror/Dell-CentOS5/.origin/Dell-CentOS5.repo  
 running: /usr/bin/reposync -l -m -d --config=/var/www/cobbler/repo_mirror/Dell-CentOS5/.origin/Dell-CentOS5.repo --repoid=Dell-CentOS5 --download_path=/var/www/cobbler/repo_mirror  

In this case the command line is :

reposync -l -m -d --config=/var/www/cobbler/repo_mirror/Dell-CentOS5/.origin/Dell-CentOS5.repo --repoid=Dell-CentOS5 --download_path=/var/www/cobbler/repo_mirror  

The process should go fine, however the return value $? is '1' which can explain why the cobbler commands fails.

Emulate bad or WAN network performances from a particular IP on a Gigabit LAN network

If you're developing Web or mobile applications, you'll certainly be confronted to poor network conditions.

The problem now is "how can I test my application under bad network conditions". Well you could rent a forein internet connection or use tools that reports performance from various remote countries however this is not a good debugging environment.

The solution is to use TC and NetEM on your front development server (typically Web or reverse proxy server), then use filters so only one client station (the debugging station) is impacted.
Don't forget to use filter otherwise all your clients will be impacted.

Below an example on how to emulate a network with :

• 1Mbps bandwidth
• 400ms delay
• 5% packet loss
• 1% Corrupted packet
• 1% Duplicate packet

The debugging client IP is 192.168.0.42  (i.e the IP impacted by the bad network performance);
The following commands need to be executed on the front developement server, please set the appropriate NIC for you environment (eth0 used below) :

 # Clean up rules  
   
 tc qdisc del dev eth0 root  
   
 # root htb init 1:  
   
 tc qdisc add dev eth0 handle 1: root htb  
   
 # Create class 1:42 with 1Mbps bandwidth  
   
 tc class add dev eth0 parent 1:1 classid 1:42 htb rate 1Mbps  
   
 # Set network degradations on class 1:42  
   
 tc qdisc add dev eth0 parent 1:42 handle 30: netem loss 5% delay 400ms duplicate 1% corrupt 1%  
   
 # Filter class 1:42 to 192.168.0.42 only (match destination IP)  
   
 tc filter add dev eth0 protocol ip prio 1 u32 match ip dst 192.168.0.42 flowid 1:42  
   
 # Filter class 1:42 to 192.168.0.42 only (match source IP)  
   
 tc filter add dev eth0 protocol ip prio 1 u32 match ip src 192.168.0.42 flowid 1:42  

To check that the rules are properly set use the following commands :

 tc qdisc show dev eth0  
 tc class show dev eth0  
 tc filter show dev eth0  

Once you're done with the testing, cleanup the rules with the command :

 tc qdisc del dev eth0 root   

There is many other options you can use (correlation, distribution, packet reordering, etc), please check the documentation available at :

http://www.linuxfoundation.org/collaborate/workgroups/networking/netem

If this setup fits your requirements, I advice you to create a shell script so you can start/stop the rules with custom values. Be aware that you can also make filters based on source/destination ports, etc.

If you have more complex requirements, you can try WANem, which is a live Linux Distribution with a graphical interface on top of NetEM. Please be aware that this requires route modifications on your client and server (or any other routing tricks).

http://wanem.sourceforge.net/
http://sourceforge.net/projects/wanem/files/Documents/WANemv11-Setup-Guide.pdf

I didn't had the opportunity to try it, please let me know if you have any feedback.

Dell DRAC Console/KVM with Chrome or Firefox

Here is a really simple trick to access to your DRAC remote console (i.e virtual KVM) with Chrome or firefox.
This trick has been tested with DRAC 5,6 and 7 only.

Requirement : You need to have a working JRE

• Log in to your DRAC Web interface, go to "System -> Console Media"
• Clic on "Launch Virtual Console"
• The browser will ask you to open or save a file, save it on your Hard Drive
• The downloaded file has the form "viewer.jnlp(x.x.x.x@x@idrac-xxxxxxx,+xxxxxxxxx,+User-xxxxx@xxxxxxxxx)"
• Rename the file "viewer.jnlp" (i.e remove the garbage data after the extension)
• Double clic on the file and you're done.

Really easy but so handy !

Hope that helps

omreport : failed to load external entity "/opt/dell/srvadmin/var/lib/openmanage/xslroot//oma/cli/about.xsl"

If you're having the following error when executing omreport :

 I/O warning : failed to load external entity "/opt/dell/srvadmin/var/lib/openmanage/xslroot//oma/cli/about.xsl"  
 error  
 xsltParseStylesheetFile : cannot parse /opt/dell/srvadmin/var/lib/openmanage/xslroot//oma/cli/about.xsl  
 Error! XML Transformation failed  

Then install srvadmin-omcommon package :

 # yum install srvadmin-omcommon  

DRAC Firmware update failed : Error: 30001 Method httpCgiErrorPage()

Have tried to update an old DRAC4 Firmware from firmware 1.5 to 1.75 via Linux binary and came to an unplaisant surprise :

 Dell Remote Access Controller 4/P  
 The version of this Update Package is newer than the currently installed version.  
 Software application name: Dell Remote Access Controller 4/P Firmware  
 Package version: 1.75  
 Installed version: 1.50  
 Continue? Y/N:Y  
 Executing update...  
 WARNING: DO NOT STOP THIS PROCESS OR INSTALL OTHER DELL PRODUCTS WHILE UPDATE IS IN PROGRESS.  
 THESE ACTIONS MAY CAUSE YOUR SYSTEM TO BECOME UNSTABLE!  
 ......................................................................................
 /tmp/duptmp.xml:6: parser error : Extra content at the end of the document  
 <SVMExecution lang = "en">  
 ^  
 /tmp/.dellSP-XmlResult12908-32487.M19124:6: parser error : Extra content at the end of the document  
 <SVMExecution lang = "en">  
 ^  
 unable to parse /tmp/.dellSP-XmlResult12908-32487.M19124  
 /tmp/.dellSP-XmlResult12908-32487.M19124:6: parser error : Extra content at the end of the document  
 <SVMExecution lang = "en">  
 ^  
 unable to parse /tmp/.dellSP-XmlResult12908-32487.M19124  

Doesn't look good and of course if I try to access the DRAC via HTTPs, I've got a nice CGI error :

 Error: 30001 Method httpCgiErrorPage()  

Looked on the web and somebody (who contacted Dell Support) advises to shutdown the server, unplug the DRAC card for a while and plug it in back... Well explain to your CTO that you need to shutdown a production server, unrack it, unplug a card just because a DRAC update failed o_O
Reference: http://lists.us.dell.com/pipermail/linux-poweredge/2008-January/034556.html

The solution that worked for me was to install the racadm Dell tool on my bastion and reset the firmware remotely.

• First install racadm :

 # yum install srvadmin-racadm4.x86_64  

Note : This is for DRAC4, didn't had the issue with newer DRAC.
Note 2 : You need to have the Dell OSMA repository installed on your server:
http://www.openfusion.net/linux/dell_omsa

•  Then run the following command :

 # racadm -rDRAC_IP -i racreset  

Note : Change DRAC_IP with your DRAC IP.
Note 2 : This operation will NOT erase your DRAC configuration.

•  Wait a while, pray, and if you're lucky as me you should be back on line (with the original firmware version of course).

Final word, I stopped being lazy and updated the firmware via the Web GUI which is a long and annoying process. Of course I used Internet Explorer as I felt like Murphy's law was around this day ^^

Hope that helps !

Yum stuck/hangs at "Running Transaction Test"

If yum is stuck at the "Running Transaction Test" step, double check that you don't have a stalled network mount (NFS,SMB,etc) somewhere.

Umount it and retry your yum/rpm command.

More info on how to umount a stalled NFS share :
http://sysnet-adventures.blogspot.fr/2013/05/umount-stalledfrozen-nfs-mount-point.html

Umount a stalled/frozen NFS mount point

NFS is known to be a little nasty when it comes to umount stalled shares.

Most of the time a simple umount doesn't work, which is a bit frustrating specially when it comes to production servers; The process just hangs and there is no way to interrupt...

Below two procedures to umount stalled  NFS shares. You should try method one before method two as it requires some network "hacks".

Method 1 :

Use a forced lazy umount, this method works 90% of the time :

 # umount -f -l /mnt/nfs_share
Note : Don't use bash auto-completion !!!  

Method 2:

This method is to be used only if method one failed.

The trick is to temporarily steal the NFS server IP adress on the NFS client (the one with stalled mount) so this client thinks that the NFS server is still alive.

Warning : Use method 1 above if your NFS server is still reachable from the NFS client. Otherwise you'll have an IP conflit and trust me you really don't want that to happen.

Let's assume the NFS server IP is 192.168.0.1

1. Double check that the NFS server is down with ping or nmap.
2. If your NFS client has very restrictive IPTables rules shut them down temporarily
3. On the NFS client, set the NFS server IP as secondary address

 # ifconfig eth0:0 192.168.0.1  
 Note : Adjust interface to your own needs  

4. Umount the NFS with a forced lzay umount

 # umount -f -l /mnt/nfs_share  
 Note : Don't use bash auto-completion !!! 

5.  Check that the NFS mount is gone
6. Remove secondary interface
   

    # ifconfig eth0:0 down  
    Note : Adjust interface to your own needs  

7. Restart IPTables if needed
8. Be happy
9. Go to sleep, it's been a long day (or night)

 If you have multiple NFS clients stalled, you can set the secondary IP on one client only.

• Client 1 : Step 1 to 5

• Client 2 to n : Step 4 and 5

• Client 1 : Step 6 to 9

This will only work if your NFS client can communicate between each others (watch for IPTables or any other filtering softwares/devices).

Hope that helps ! (that helped me a lot :)