Recent Blog Posts

virsh – management user interface

Synopsis virsh [ OPTION ]… [ COMMAND_STRING ] virsh [ OPTION ]… COMMAND [ ARG ]… Description The virsh program is the main interface for managing virsh guest domains. The program can be used to create, pause, and shutdown domains. It can also be used to list current domains. Libvirt is a C toolkit to interact with the virtualization capabilities of recent versions of Linux (and other OSes). It is free software...

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Apache empty semaphores

Apache will not start. Error log contains:- [emerg] (28)No space left on device: Couldn’t create accept lock or [crit] (28)No space left on device: mod_rewrite: could not create rewrite_log_lock Configuration Failed Checking your disk shows that you have plenty of space. The problem is that apache didn’t shut down properly, and it’s left myriads of semaphore-arrays left, owned by my apache-user. Run:- ipcs -s | grep...

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Manual Routes on VLAN’s

Sometimes when you have a subnet accessible from an interface that is not along the default gateway (such as a group of private routed subnets in 10.x.y.z), you need to add a manual route. Say for example vlan 2 is on 10.1.0.0/16 and has a router on 10.1.1.1 that also serves 10.2.0.0/16.  You cant put a GATEWAY=10.1.1.1 in the ifcfg-eth0.2 file, since that will (potentially) override the GATEWAY setting in ifcfg-eth0 that reaches the Internet...

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Bridging over VLAN’s

What? As if you weren’t confused enough already, now let’s combine the two concepts and create a bridge across a VLAN. That would be a bridge between two ethernet interfaces, where one is a real ethernet card in the PC (or a wifi, or some other regular type of ethernet interface), and the other will be a VLAN interface. Why? Let’s say you have a piece of equipment which by itself doesn’t know how to talk VLAN -but you...

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VLAN’s

What is a VLAN? VLAN is short for Virtual LAN (where LAN is short for Local Area Network). The virtual lan is pretty much what is sounds like – a virtual seperate network, but across the same physical network. Confused? Okay, think of it like separate conference rooms. Some computers are plugged into conference room A and can chat, some into conference B and can chat, but A and B can’t hear each other. Now do this in the same room,...

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