A volume mount CVE was discovered in Kubernetes 1.9 and older which allowed access to node file system using emptyDir volume mount using subpath. The official description goes as follows: In Kubernetes versions 1.3.x, 1.4.x, 1.5.x, 1.6.x and prior to versions 1.7.14, 1.8.9 and 1.9.4 containers using subpath volume mounts with any volume type (including non-privileged pods, subject to file permissions) can access files/directories outside of the volume, including the host’s filesystem. ...

If you are using cobra cmd line library for golang applications and it’s PersistentFlags and if you have a use case where you are adding same kind of flag in multiple places. You might burn your fingers in that case, if you keep adding it in multiple sub-commands without giving it a second thought. To understand what is really happening and why it is happening follow along. All the code referenced here can be found here https://github.com/surajssd/cobrademo. ...

I have this old PC Dell Inspiron 1525 with 2GB RAM and 32 bit dual core processor and I wanted to install fedora on it, but I cam accross few problems which I am documenting for further reference. Wifi device not detected The wifi drivers are not loaded by default, so followed this blog, basically do following: export FIRMWARE_INSTALL_DIR="/lib/firmware" wget http://mirror2.openwrt.org/sources/broadcom-wl-5.100.138.tar.bz2 tar xjf broadcom-wl-5.100.138.tar.bz2 cd broadcom-wl-5.100.138/linux/ sudo b43-fwcutter -w /lib/firmware wl_apsta.o Slow boot problem Since the boot process is very slow so add this line to /etc/default/grub ...

NOTE: There is an updated version of this blog here. Few days back I wrote a blog about adding new node to the cluster using the static token file. The problem with that approach is that you need to restart kube-apiserver providing it the path to the token file. Here we will see how to use the bootstrap token, which is very dynamic in nature and can be controlled by using Kubernetes resources like secrets. ...

I enabled PodSecurityPolicy on a minikube cluster by appending PodSecurityPolicy to the apiserver flag in minikube like this: --extra-config=apiserver.enable-admission-plugins=Initializers,NamespaceLifecycle,\ LimitRanger,ServiceAccount,DefaultStorageClass,DefaultTolerationSeconds,\ NodeRestriction,MutatingAdmissionWebhook,ValidatingAdmissionWebhook,\ ResourceQuota,PodSecurityPolicy Ideally when you have PSP enabled and if you don’t define any PSP and authorize it with right RBAC no pod will start in the cluster. But what I saw was that there were some pods still running in kube-system namespace. $ kubectl -n kube-system get pods NAME READY STATUS RESTARTS AGE coredns-576cbf47c7-g2t8v 1/1 Running 4 5d11h etcd-minikube 1/1 Running 2 5d11h heapster-bn5xp 1/1 Running 2 5d11h influxdb-grafana-qzpv4 2/2 Running 4 5d11h kube-addon-manager-minikube 1/1 Running 2 5d11h kube-controller-manager-minikube 1/1 Running 1 4d20h kube-scheduler-minikube 1/1 Running 2 5d11h kubernetes-dashboard-5bb6f7c8c6-9d564 1/1 Running 8 5d11h storage-provisioner 1/1 Running 7 5d11h Which got me thinking what is wrong with the way PSPs work. So if you look closely only two pods are scheduled by a deployment. ...

I passed CKA exam with 92% marks on 19th October 2018. A lot of folks are curious about how to prepare and what resources to follow. Here is my list of things to do and list of resources that might help you on successful CKA exam. The duration of exam is three hours, which is enough time if you do good practice. The exam is pretty straight forward and tests your Kubernetes hands-on knowledge, so whatever you read please try to do it on a real cluster. ...

I am about to attempt the CKA exam and it has a browser based terminal. And I am used to this terminal shortcut Ctrl + W which deletes a word. But the same shortcut in browser can close a tab. Since this exam is combination of both I am afraid I might close my exam tab while deleting a word in terminal. Now the only solution to this is disabling the shortcut in chrome. But turns out that the shortcut is hard coded in chrome. ...