Simon Krenger

OpenShift: Add or remove label

So when using NodeSelectors in OpenShift, you’ll also have to set labels on your nodes. You can find more information on labeling nodes in the OpenShift documentation. Here is how you can add or remove a label from a node or pod:

To add a label to a node or pod:

# oc label node node001.krenger.ch mylabel=myvalue
# oc label pod mypod-34-g0f7k mylabel=myvalue

To remove a label (in the example “mylabel”) from a node or pod:

# oc label node node001.krenger.ch mylabel-
# oc label pod mypod-34-g0f7k mylabel-

You can also use oc label -h to see more options for the oc label command.

Release of “MySQL 8 Recipes”

In the past few months, I worked closely with Packt Publishing to create a new video course for MySQL 8. Today, the video course was released into the world. I am pround to present to you the new video course “MySQL 8 Recipes“:

In this video course, I tried to include the most common tasks for database administrators while focussing on the new features of MySQL 8. I included the following main chapters:

  • Install and configure a new MySQL 8 database
  • Upgrade existing databases to MySQL 8
  • Perform typical administration tasks
  • Master the new querying features in MySQL 8
  • Perform performance-tuning tasks
  • Optimize your database
  • Access databases with PHP, Python, or Java

The video course was released under ISBN-13 9781788393638 and is available per now. Of course, since MySQL 8 is still under development, there will hopefully be many other new features in the new release. But I hope you enjoy this video course. Purchase it here.

Oracle example schema for MySQL

Anyone who has worked with Oracle has encountered the Oracle “hr” schema in one way or another. The Oracle example schema provides a few simple tables with example data to test out some queries or learn SQL.

So when working with MySQL, I like to have the same schema as well. Luckily, Andrei Ciobanu feels the same way and he provides a wonderful adaptation of this sample schema for MySQL on his website: HR Schema for MySQL and Maria DB.

The SQL script for the schema can be found on GitHub: nomemory/hr-schema-mysql (or in my fork: simonkrenger/hr-schema-mysql).

Thank you Andrei!

“CrashLoopBackOff” and how to fix it

So in any larger docker installation, be it Kubernetes or OpenShift, you will encounter pods that crash regularly and enter the “CrashLoopBackOff” status.

$ oc get pod --all-namespaces 
NAMESPACE         NAME                       READY     STATUS             RESTARTS   AGE
[..]
my-project-1      helloworld-11-9w3ud        1/1       Running            0          7h
my-project-2      myapp-simon-43-7macd       0/1       CrashLoopBackOff   3774       9h

Note the container that has status “CrashLoopBackOff” and 3774 restarts.

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Workaround for WMI client over IPv6

Some years ago, I wrote some examples for the WMI client on Linux. I still get a lot of queries from people trying to use the WMI client to access Windows hosts and I am often happy to help if there are any problems.

One of the latest problems occurred when trying to access a Windows host over IPv6:

$ wmic -U 'user%password' //FD00:180::0:0:0:0:0 "Select Caption From Win32_OperatingSystem"
[..]
UNKNOWN - The WMI query had problems. The error text from wmic is: [librpc/rpc/dcerpc_util.c:343:dcerpc_parse_binding()] Unknown dcerpc transport 'FD00'
[librpc/rpc/dcerpc_connect.c:337:dcerpc_pipe_connect_ncacn_ip_tcp_recv()] failed NT status (c0000017) in dcerpc_pipe_connect_ncacn_ip_tcp_recv
[librpc/rpc/dcerpc_connect.c:828:dcerpc_pipe_connect_b_recv()] failed NT status (c0000017) in dcerpc_pipe_connect_b_recv
[wmi/wmic.c:196:main()] ERROR: Login to remote object.
NTSTATUS: NT_STATUS_NO_MEMORY - Memory allocation error

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