We’ve had a problem with some of our KVM Virtual machines where the network connection just disappears. The vm is still running but essentially it’s unreachable over the network (just like if you have pulled out the network cable of real computer). Until, I found the fix, I had to connect to the VM using … Read more
The key to blocking a specific IP address with UFW is to make sure that the rule which blocks the ipaddress is applied before any allow rules. Because the firewalls rules are run in order – the block will no come into affect if it appears at the bottom. For example on most webserver you … Read more
I generally setup binary logs on a MySQL server where the data isn’t being replicated and I’m using daily mysql-dumps to backup the data. This allows me to recover the database to a specific point in time. However sometimes the binary logs can become very large if there are lots of changes occuring to the … Read more
When you are trying to analyse disk usage there are a limited set of command line tools on Linux. Most people use either of ‘find’ or ‘du’. However using these tools it can be a lot of work to get an overall picture and drill down into directories to find the problems. Enter ncdu (short … Read more
I tried upgrading one of our servers from Apache 2.2 -> Apache 2.4. It didn’t work so I purged the PPA but the configurations needed rolling back too (which ppa-purge command didn’t do). So, to completely remove Apache2 configuration files and reinstall them use the following command: and then had to also reinstall php5: Hope … Read more
There isn’t a simple command to rename a mysql database. You just need to create a new database and then rename all the tables like so: There is also an alternative method by dumping the old database and importing it again like so: I have found the second option to be alot faster both in … Read more
If you have a wildcard certificate (for example *.randomhacks.co.uk) you might need to install it on multiple servers which host the different subdomains. Basically, don’t rekey the certificate for each server just copy the same keys and certificate files across all the servers. If you rekey the certificate each time then you will invalidate any … Read more
I’ve just installed an Ubuntu apt-cache server on our local network to speed up downloading packages each time we install or upgrade an Ubuntu computer. However, changing all the /etc/apt/sources.list file for every computer in the office is a real pain. Here is a simple command using sed which does this automatically for you: The … Read more
I usually make the hard drives on my virtual machines as small as possible to save disk space on the host. I do this because it is reasonably easy to resize them at a later date (especially if you using LVM). Anyhow here is a quick guide to resizing a qcow2 disk image. 1 – … Read more
I’ve been getting an error when I type “sudo su”. It says: This was caused by the shell for root was incorrectly set. To fix it, I edit the passwd: Then I edited the line for root from: to