Simon Krenger

So when working with a lot of different namespaces in Kubernetes and you only know the “oc project” command from OpenShift, you start to miss an easy way to change namespaces in Kubernetes.

The official documentation to switch namespaces proposes something like this:

$ kubectl config set-context $(kubectl config current-context) --namespace=<insert-namespace-name-here>

Not something that I want to type regularly. First I tried to create a BASH alias or something, which did not work. So I looked around for BASH functions. I found that Jon Whitcraft proposed a nice BASH function in a GitHub issue. I lightly modified this and placed this in my own .bashrc file:

function kubectlns() {
  ctx=`kubectl config current-context`
  ns=$1

  # verify that the namespace exists
  ns=`kubectl get namespace $1 --no-headers --output=go-template={{.metadata.name}} 2>/dev/null`
  if [ -z "${ns}" ]; then
    echo "Namespace (${1}) not found, using default"
    ns="default"
  fi

  kubectl config set-context ${ctx} --namespace="${ns}"
}

So to change your namespace, use something like this:

$ kubectlns simon
Context "kubernetes-admin@kubernetes" modified.

Nice and short.

For Nagios, many, many Oracle plugins are available for checking database availability and performance. But if you just want to check if the instance is up and running (and not add more complexity), you can use the simple script provided here.

In an earlier post, I showed how to install SQL*Plus on Debian and based on that tutorial, I wrote a little shell script to query a database (I called it check_oracle_dual.sh):

In a script I was working on, the tar command always reported the following error when I tried to extract an archive:

Cannot change ownership to uid 1000 , gid 1000: Permission denied

But I was executing the script as root! The reason for this error to occur turned out to be relatively simple. Hint: It has to do with CIFS.

In a previous post I showed how to install the Windows Management Instrumentation (WMI) client for Linux (wmic). In this post, I wish to show a few ways on how to query a Windows-based host using the WMI client.

Using WQL, we can query almost any aspect of the Operating System. Using the available WMI Classes (for example the WMI Win32 Classes), we can easily query performance indicators such as Memory Usage, Disk Usage or the status of a certain process.

On one of our Debian hosts, we use bash scripts and cron jobs to automate certain tasks. One of these bash scripts downloads files from an FTP server and archives them. After upgrading the host machine to Debian 6.0.4, one of the bash scripts suddenly showed warnings:

/srv/foo/bar.sh: line 146: warning: here-document at line 140 delimited by end-of-file (wanted `EOF')

Whoops, so let’s look into it. The change was probably introduced with the new version of bash:

Well, I was quite busy before the holidays, but here is another post I just keep for my reference.

For each database, I believe it is important to automate database shutdown and database startup. This way, in case of an emergency, a systems administrator can start and stop database services without the need for a database administator. Oracle provides an excellent article on this topic, but the Oracle documentation is quite generic. So I hereby provide a step-by-step guide for Red Hat Enterprise Linux (RHEL).

For a startup script, I needed to start JBoss and start another component as soon as the complete JBoss server was started. When you execute the “run.sh” script that comes with JBoss, it immediately exits and starts JBoss in the background (which is quite nice I think). Unfortunately, when I started the other component using this method, the additional program was unhappy, since JBoss was not ready yet. So I had to come up with a trick to delay the start of the additional program.

So with the help of the internet and my co-worker, we came up with the following script:

Coming from Linux distributions where BASH is usually already set up and configured, I had to find my way around in a UNIX environment first. So here I present the files necessary for a proper installation of BASH under Solaris 10 (yes, I know Solaris 11 Express is out :)).

So after installing the BASH package (see my other post on setting up Solaris), you might find your new shell to be kinda boring. Also, it simply shows up as bash-3.00#, which by itself does not tell you a lot. So lets improve it a bit.