RedHat – YUM Error: database disk image is malformed

As mentioned in one of my posts RedHat – Rebuild corrupted rpmdb today I have seen different error related to YUM/RPM. Clean the YUM dbcache. Rebuild the rpmdb.

RedHat – Useful YUM and RPM commands

Install the package YUM installs the package if it is not already present and updates it with the latest version available from repo if the package already installed and present. #yum install <package> Check which package (available from repo) provides the binary file/command. #yum provides <binary file/command> Often we want to see what are the …

AWS EC2 Linux Boot Problems – Root Volume

Below are the step by step instructions to recover EC2 instance if the system is not able to boot properly. So far I have seen couple of scenarios where it helped: -          Corrupted latest kernel ( initrd image is missing ) -          Not able to mount File system because of wrong entry in /etc/fstab and …

Docker – Sharing data between containers

Procedure 1: Using Data Containers Step 1 - Create Container Data Containers are containers which sole responsibility to be a place to store/manage data. Like other containers they are managed by the host system. However, they don't run when you perform a docker ps command. To create a Data Container we first create a container with a …

Docker – difference between CMD and ENTRYPOINT

The CMD line in a Dockerfile defines the default command to run when a container is launched. If the command requires arguments then you need to use an array, for example ["cmd", "-a", "arga value", "-b", "argb-value"], which will be combined together and the command cmd -a arga value -b argb-valuewould be run. An alternative approach to CMD is ENTRYPOINT. While …

Kubernetes – Install Master Node

  I have prepared the bash script to execute all the commands necessary to install on Kubernetes master server. Check the last command to switch off swap. I have seen this below error when running the #kubeadm init with swap on. #kubeadm init As mentioned in above screenshot - We need to copy the configuration …

Linux – Users and Groups – Part 2

Part 1 of Linux Users and Groups is here: Linux – Users and Groups – Part 1  where we discussed User accounts. Moving on to Part 2 lets talk about Groups. In Part 1 we have seen creating group and creating user in that group. We could see that from "/etc/passwd" that oracle user id is …

RedHat – Rebuild corrupted rpmdb

The "rpmdb" is broken and not able to run any of the rpm commands. #rpm -qa rpmdb: Thread/process 3392/140287890028448 failed: Thread died in Berkeley DB library error: db3 error(-30974) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery error: cannot open Packages index using db3 -  (-30974) error: cannot open Packages database in /var/lib/rpm rpmdb: Thread/process …

Linux – Users and Groups – Part 1

Ok.. Lets start with creating a group called "dba" and create user "oracle" belongs to "dba" group. We could see that from "/etc/passwd" that oracle user id is 1521 and primary group id is 5000. But we haven't set the password yet for "oracle" user. If we watch closely "/etc/shadow" password the second column is !! which …

AWS Autoscaling – Min Desired Max

As mentioned here : https://stackoverflow.com/questions/36270873/aws-ec2-auto-scaling-groups-i-get-min-and-max-but-whats-desired-instances-lim MIN: This will be the minimum number of instances that can run in your auto scale group. If your scale down CloudWatch alarm is triggered, your auto scale group will never terminate instances below this number. DESIRED: If you trip a CloudWatch alarm for a scale up event, then it …