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VMware VCA certfications: FREE voucher
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5 months, 4 weeks ago

If you are interested in VMware VCA Certifications for Cloud, Datacenter Virtualization and Workforce Mobility, take a look at Josh Odgers website, there's a free voucher (until January 2014) to take all the 3 exams that is waiting for you!

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Relocating Cagliari Language Network
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9 months, 3 weeks ago

I've just finished moving the Cagliari Language Network website from Openshift to a dedicated machine on the Aruba Cloud. It has been running on Openshift for 1 year almost without any problem, but recently it started being very slow and some users were complaining about that.

Now, even if it is running on a small (1 CPU, 1GB ram, 10GB storage) and cheap CentOS 6 Hyper-V VM, performances seem to be a lot better than before.

The migration started almost 2 weeks ago, but I decided to switch the DNS records only today because I was testing Varnish in front of our Apache.
During the tests I noticed that cache hits were very high and I didn't find any particular problem on our setup, so today I decided it was time to complete the migration and try it on production.

The other big news is that I've started working on a new CLN website. The new one won't be based on Wordpress anymore but it will be a custom Django application. The idea is to make language feeds available through REST API so in the future we can build mobile applications on top of them.

If you have any suggestion or if you notice any problem about the website feel free to contact me or one of our admins.

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RHEL6 asymmetric routing
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12 months ago

If you have tried configuring your Red Hat Enterprise Linux 6 with 2 different IPs of the same network using different network interfaces you probabily noticed that it doesn't work very well. Or it doesn't work at all!

That's because, by default, RHEL6 (unlike RHEL5) drops packets when the route for outbound traffic differs from the route of incoming traffic.

At this point you have 2 solutions. The first one is to accept asymmetrically routed packets setting

net.ipv4.conf.default.rp_filter = 2

on /etc/sysctl.conf.

But the best solution is to configure a source based routing.
For an explanation and practical examples you can read (and you should) this article or, if you are just impatience, you can run the following commands (assuming that you have 2 interfaces, eth0 and eth1, with 192.168.16.20 and 192.168.16.21 respectively and gateway 192.168.16.1):

# echo "default via 192.168.16.1 dev eth0 table 20" > /etc/sysconfig/network-scripts/route-eth0
# echo "from 192.168.16.20 table 20" > /etc/sysconfig/network-scripts/rule-eth0
# echo "default via 192.168.16.1 dev eth1 table 21" > /etc/sysconfig/network-scripts/route-eth1
# echo "from 192.168.16.21 table 21" > /etc/sysconfig/network-scripts/rule-eth1

and then restart your interfaces:

# service network restart

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Arabic A1 Certification
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1 year, 1 month ago

After 100 hours of Arabic A1 lessons attended at the Centro Linguistico d'Ateneo I've passed the final exam with a score of 52/60.
It hasn't been easy studying and attending all the lessons while working, but it was definitely worth it!

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VCenter 5.1 services start-up order
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1 year, 6 months ago

With the release of VMware vSphere 5.1 some additional components are required when deploying a vCenter server: the vCenter Single Sign On and the vCenter Inventory Service.

If you decide to install everything, database included, in one Windows system you should fix the services start-up order or, sooner or later, your vCenter won't automatically start after a reboot because of a race condition.

Previous VMware instructions must be a little bit modified to include the new components. The right start-up order is the same as the installation order:

  1. SQL Database (MSSQLSERVER)
  2. vCenter Single Sign On (ssotomcat)
  3. vCenter Inventory Service (vimQueryService)
  4. vCenter Server (vpxd)

To achieve that on Windows 2003 (but it is probably the same on newer Windows versions) you need to modify the windows registry.

Using regedit go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ssotomcat, create a new Multi-String Value called DependOnService and add MSSQLSERVER (or the name of your MSSQL Server instance) as a value data. This ensure that the vCenter SSO service will start after the MSSQL instance.

For the vCenter Inventory Service go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\vimQueryService and add ssotomcat as a service dependence.

For the vCenter Server itself go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\vpxd and ensure that the DependOnService key contains the following entries:

ProtectedStorage
lanmanworkstation
MSSQLSERVER
ADAM_VMwareVCMSDS
ssotomcat
vimQueryService

Additionally, if you have the "VMware USB Arbitration Service service hung on starting" error go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\VMUSBArbService and add the MSSQLSERVER string to the DependOnService key.

To verify that the dependencies were added go to the services.msc snap-in, click on the corresponding service and check the dependencies tab.

This should be enough to fix the dependencies problem of the vCenter 5.1 until VMware will release a patch for that.

By the way, if you are wondering why the start-up is so slow read vCenter Server 5.1 start up may take longer than previous versions.

References: VMware KB 2035933, VMware KB 1007669, VMware KB 2034975