Performance tuning with tuned and tuned-adm in Redhat and CentOS
The tuned is a dynamic adaptive system tuning daemon running on Redhat or CentOS. It can adapt the operating system to perform better under certain workloads by setting a tuning profile.
How to set custom login banner message in linux
SSH banner messages are necessary when you want to display a warning for users when they access a server over SSH.
Wipe signature from a device
wipefs can erase filesystem, raid or partition-table signatures (magic strings) from the specified device to make the signatures invisible for libblkid.
-a, –all
Erase all available signatures. The set of erased signatures can be restricted with the -t list option.
-f, –force
Force erasure, even if the filesystem is mounted. This is required in order to erase the partition table on a block device.
1 | $ wipefs -a /dev/nvme0n1 |
How to upgrade Linux kernel on Ubuntu
Method 1: Use System Update Process (Automatic Procedure)
Update System Packages
1
$ sudo apt update
This command retrieves information about the latest available package versions from the repositories configured on the system.
Run the upgrade
Run the following command to upgrade the installed packages, including the kernel, to the latest versions available in the repositories:
1
$ sudo apt upgrade
How to use kubectl to manage kubernetes cluster contexts
Kubernetes context
A context in kubernetes is used to group access parameters under a convenient name. Each context has three parameters: cluster, namespace, and user. By default, the kubectl command-line tool uses parameters from the current context to communicate with the cluster.
The complete explanation for await, svctm and %util in iostat
iostat is a Linux I/O performance monitoring utility. It’s very commonly used to analyze device utilization.
Understanding EC2 Instance and Storage Volume Types
Does 100% utilization really mean the disk bottleneck?
From man page of iostat in Linux, %util is explained as below.
%util:
Percentage of elapsed time during which I/O requests were issued to the device (bandwidth utilization for the device). Device saturation occurs when this value is close to 100%.
I have seen many cases people misuse this metric when to tell if the system runs into disk I/O bottleneck.