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We are moving!

Roses are red, temps fugit and we are moving! The new blog URL is . Hoping to see you there. Cheers! Advertisements

“Cannot allocate memory” error when starting a Xen guest

When trying to start a Xen guest, having plenty of primary memory I got the following error message: Error starting domain: POST operation failed: xend_post: error from xen daemon: (xend.err “Error creating domain: (12, ‘Cannot allocate memory’)”) In this case it was very useful comparing the assigned memory of the Domain-0 (which “contains” all the […]

Reaching the open files limit of a Qpid server with simple Nmap requests

I recently noticed a curious behavior of Apache Qpid Messaging server 0.20 while performing some simple nmap checks: while true; do   echo “$(date +’%Y/%m/%d-%H:%M:%S’) $(nmap -p 5672 qpid_server | grep ‘^5672\/tcp’)”   sleep 0.5 done Qpid’s log started growing very fast and very soon it was flooded with many (really, many: hundreds of thousands) lines […]

Using sudo with NRPE requests

I want to receive an alert whenever root’s crontab of a machine has been updated. In RHEL (Red Hat Enterprise Linux) 6 the crontab is stored in /var/spool/cron/root and it is only readable/writable for root itself. After installing the required yum packages (examples: nagios-plugins-all, nagios-plugins-nrpe, nrpe) you can begin this implementation by checking if the […]