Month: April 2012

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Grub Fallback: Boot good kernel if new one crashes

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grub featured

It’s hard to believe but I didn’t know about Grub fallback feature. So every time when I needed to reboot remote server into a new kernel I had to test it on local server to make sure it won’t panic on remote unit. And if kernel panic still happened I had to ask somebody who has physical access to the server to reboot the hardware choose proper kernel in Grub. It’s all boring and not healthful – it’s much better to use Grub’s native fallback feature. … Read more

Home » 2012 » April

Why Mosh is better than SSH?

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command line

Mosh (stands for Mobile Shell) is replacement of SSH for remote connections to Unix/Linux systems. It brings a few noticeable advantages over well known SSH connections. In brief, it’s faster and more responsive, especially on long delay and/or unreliable links. Key benefits of Mosh Stays connected if your IP is changed. Roaming feature of Mosh allows you to move between Internet connections and keep Mosh session online. For example, if your wifi connection changes IP you don’t need to reconnect. Keeps session after loosing connection. … Read more

Home » 2012 » April

Attach ISO image stored in XenServer local storage

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xen server featured

Citrix XenServer is powerful hypervisor that is based on Linux (Redhat/Centos/Fedora family) and competes with Vmware ESXi and offer wide range of virtualization features for data centers. In general you can do a bare-metal installation of XenServer to your hardware server and create multiple virtual machines (VMs) inside XenServer host. Obviously you’ll need to have the possibility to boot VM from DVD-Rom to start installation of, let’s say, Linux Mint. You can do it using hardware DVD-Rom of the host XenServer or attach ISO image and … Read more

Home » 2012 » April

Track Cisco BGP peers using Nagios

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Nagios (featured logo)

Few will deny that monitoring of Cisco devices is essential part of sysadmin’s job. I personally use Nagios to track states of BGP neighbors on Cisco routers so if one of peers goes down I’ll receive a phone call from Nagios. You may have redundant network topology but it still makes sense to know when peer goes offline, how often it happens and how fast failover router (if any) pick-ups the traffic from failed peer. There are a few plugins for Nagios to monitoring BGP … Read more

Home » 2012 » April

Top Open Source IP Address Management Software

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ipplan feat

In this post you will find top open source software for IP address management (IPAM). If you are sysadmin at organization that holds pool of IP addresses and allocates its parts to clients then you must use IP address management tools to track used, reserved, allocated or free IP addresses. It usually prevents an overhead and allows to have clear picture of IP addresses resources usage within an organization on the whole. For example, it may be useful to know how many free IP networks are … Read more