Symptoms Networking on the host machine is still functioning properly, but all networking stops working on your KVM virtual machines. You can’t even get dhclient to work in a VM. Even if you manually assign an IP address and default route to a VM, it still can’t ping its gateway. Rebooting the virtual machines does… Read More »
…Even Google does it. I’m talking about load balancing via DNS. If you find yourself in a situation where one server isn’t cutting it anymore and you would like to easily distribute load across several servers with identical configuration answering to the same backend, one way to accomplish it is to use round-robin DNS. It’s even easier… Read More »
Disclaimer: Like some of my other posts here, I’ve shared this snippet on other websites out there. Still, I reserve the right to re-use my own material 😉 OK then. There have been times in the past when it was necessary for me to convert a VirtualBox disk file to a format that I could… Read More »
Typically the w command will show you who is logged in. So do the users and who commands. With the advent of Ubuntu’s unity and the lightdm desktop session manager, these commands don’t tell the whole truth. Moreover, users don’t need to be logged in to a terminal (or pseudo terminal) in order to run… Read More »
Friends, you should encrypt. So, search for a nice tutorial about how to set up GPG for yourself and get to it. If you prefer to start out easily without learning to use gpg from the command line, Ubuntu/Mint/Debian all provide great GUI tools, such as the built in "Passwords And Keys" utility, easily found… Read More »
First, you’ll need to use the visudo utility… sudo visudo This command safely opens up the /etc/sudoers file for you in your default editor. Let’s say you want to allow a user named “joe” to run a given command. You just need to add a line like this below (customize for your needs) joe ALL=(ALL)… Read More »
…Reinstall it! sudo dpkg remove –purge vnc4server && sudo apt-get -y install vnc4server That has always fixed the problem for me when I’ve had such troubles.
Go ahead and skip right to the examples if you’re in a hurry 😉 perl -p -i -e ‘s/change this/to that/g’ file1 file2 file3… Got Regexes? Regular Expressions (also known as regexes, regexen, and regexps) open up a world of new power tools to you when you need to automate text analysis or manipulations such… Read More »
Please feel free to experiment with the following ~/.bash_profile goodness of my own, and save away to yours what tasty morsels that you find useful. Exactly what each line does below is left as an exercise to the reader 😉 but to summarize— these aliases speed up common tasks, keep embedded timestamps in your history,… Read More »
denyhosts is an excellent utility to prevent brute-force SSH attacks against your server. One shortcoming it has is that it is difficult to get a blacklisted IP address back out of the, well, blacklist. Simply removing its entry from /etc/hosts.deny will not keep denyhosts from doing its job of blocking what it deemed to be… Read More »