Now and again, there is a need to override certain DNS lookups. For individual systems you could make changes in the hosts file, but this does not scale well and is easily forgotten. Establishing the override through DNS, one could either use split-view DNS or the old-school strategy of creating a stub zone for that exact hostname (or domain, if you were lucky), but this does not scale very well either and is, let’s admit it, rather ugly.
That said, ... [continue reading]
I tend to dislike scattering my file-systems with non-packaged script modules, be it Python, Perl, or Ruby. So I wrap rpm packages for my systems. But packing is such a bother, you might say. That might be true, but luckily, we have good tools to help us.
To build this website, we used Jekyll, an excellent small ruby HTTP server for static content. Jekyll is available as a standard Ruby gem, but not as rpms ... [continue reading]
Migrating disk volumes to new storage solutions can be a bit of a chore. Cloning file systems are usually done after taking your system offline in order to preserve consistency. But every so often you simply can’t afford to have your data or system unavailable for that period of time. So what to do?
We had invested in new SAN storage solution and had to move the disk volumes for our virtual machines from the old SAN ... [continue reading]
pv is a nice little tool that will take stdin and make a nice little progress bar and displaying time elapsed, percentage completed (if size is known) current throughput rate and the total data transferred and with an ETA.
So if you have a tool that can output it’s result on standard output or read from standard input, one can get a progress bar!
It’s nice to know that “data is flowing”.
... [continue reading]
I come back to a specific problem every once in a while: Changing a program’s file descriptor while the same program is running.
From time to time, we do stupid things, like running a very important shell command, and adding debug output to see that it works, then realizing that it will take hours to finish, and spitting gigabytes of debug to an xterm through SSH does not help. The dream is of course to ... [continue reading]
Rsync is a versatile tool for copying files or whole directory trees locally or over the network to another computer. rsync -a will copy files and ensure most of attributes, ownership and permissions are carried over. Rsync over network is trivial, with SSH as the default network protocol (Rsync can also run in daemon mode).
Often I need to do a rsync -a between hosts on directories I’m not the ... [continue reading]
So, you are stuck in a shell, debugging some random problem. And you have to navigate between two directories, iterating through a debug session - say between a configuration directory like /etc/apache/sites-available and a log directory like /var/log/apache.
Any sane person would open another shell, but in this case you can’t. Or just couldn´t be bothered. So you are stuck in that shell typing in cd /var/log/apache, checking the log-file, then typing in ... [continue reading]
Have you ever had the need to take a rear-view mirror look at your network traffic, for instance for finding out which of your servers were contacted by some remote IP address a week ago? Or to establish whether or not a recently compromised server was able to further distribute its malware? Perhaps you need to find out which single IP address congested your network yesterday evening? How about finding each day’s bandwidth usage for the VoIP telephone system? Has ... [continue reading]
Welcome to our new techblog. This microsite will contain tech-related entries which interests the techies (and other employees) at Redpill Linpro.
We hope you enjoy the articles!
