Top 10 videos from Red Hat Developer

Podman: A Linux tool for working with containers and pods Get started with Podman, an open source, Linux-based tool that builds Docker-compatible container images.

Easily secure your Spring Boot applications with Keycloak Discover how to deploy and configure a Keycloak server and then secure a Spring Boot application.

Learn how to move your existing Java app to Kubernetes—without changing a single line of code Using the free Developer Sandbox for Red Hat OpenShift, we demo how you can take your existing source code or create a new application and easily deploy and manage them as containers.

KBE Insider (E3): Luke Hinds We talk to Luke Hinds, Security Lead for Office of CTO, Red Hat, about his work on the Kubernetes Security Response Team, Sigstore, and the Kubernetes HackerOne Bug Bounty Program.

Local OpenShift environment on Windows with Red Hat CodeReady Containers Brian Tannous walks through getting a local OpenShift environment installed on Windows using Red Hat CodeReady Containers.

Securing apps and services with Keycloak authentication | DevNation Tech Talk See how to easily secure all of your applications and services, regardless of how they’re implemented and hosted, with Keycloak—all with little-to-no code required.

A deep dive into Keycloak | DevNation Tech Talk This tutorial introduces Keycloak, an open source identity and access management solution for modern applications and services.

Secure Spring Boot Microservices with Keycloak | DevNation Tech Talk In this interactive, live-coding session, you’ll explore the Spring Boot adapter provided by Keycloak.

KBE Insider (E5): Savitha Raghunathan We talk to Savitha Raghunathan, Senior Software Engineer at Red Hat, about her work and experience as an open source contributor within the Kubernetes ecosystem.

Apache Kafka + Debezium | DevNation Tech Talk This tutorial explores how to use Apache Kafka and Debezium. Learn how to use change data capture for reliable microservices integration.

Install and Enable EPEL Repository for CentOS 7.x

The EPEL is an acronym for Extra Packages for Enterprise Linux. The EPEL repository used by the following Linux Distributions:

  • Red Hat Enterprise Linux (RHEL)
  • CentOS
  • Oracle Linux

On the Terminal,

Install EPEL Repository

# yum -y install epel-release

Refresh EPEL Repository

# yum repolist

Install Packages from EPEL Repository

# yum install -y htop

Search and install Package (E.g. htop)

# yum --disablerepo="*" --enablerepo="epel" list available | grep 'htop'

CentOS Replacement Rocky Linux Is Now in GA and Under Independent Control

The Rocky Enterprise Software Foundation (RESF) is announcing the general availability of Rocky Linux, release 8.4, designed as a drop-in replacement for the soon-to-be discontinued CentOS. The GA release is launching six-and-a-half months after Red Hat deprecated its support for the widely popular, free CentOS server operating system.

HPC Wire 21-June-2021 ()

For more information, do take a look at CentOS Replacement Rocky Linux is now in GA and Under Independent Control

Do take a look at Rocky Linux site

Finding physical cpus, cores and logical cpus

Number of Active Physical Processors

% grep physical.id /proc/cpuinfo | sort -u | wc -l
8

Number of cores per CPU

% grep cpu.cores /proc/cpuinfo | sort -u
cpu cores       : 26

Therefore the total number of cores is
8×26 = 208 cores

Number of Logical Processors

The number of cores seen by the Linux. Since the Server has switched on Hyperthreading

% grep processor /proc/cpuinfo | wc -l
416

References:

  1. How to find the number of physical cpus, cpu cores, and logical cpus

Understanding Load Average in Linux

Taken from RedHat Article “What is the relation between I/O wait and load average?” I have learned quite a bit on this article.

Linux, unlike traditional UNIX operating systems, computes its load average as the average number of runnable or running processes (R state), and the number of processes in uninterruptable sleep (D state) over the specified interval. On UNIX systems, only the runnable or running processes are taken into account for the load average calculation.

On Linux the load average is a measurement of the amount of “work” being done by the machine (without being specific as to what that work is). This “work” could reflect a CPU intensive application (compiling a program or encrypting a file), or something I/O intensive (copying a file from disk to disk, or doing a database full table scan), or a combination of the two.

In the article, you can determine whether the high load average is the result processes in the running state or uninterruptible state,

I like this script…… that was written in the knowledgebase. The script show the running, blocked and runnin+blocked.

[user@node1 ~]$ while true; do echo; uptime; ps -efl | awk 'BEGIN {running = 0; blocked = 0} $2 ~ /R/ {running++}; $2 ~ /D/ {blocked++} END {print "Number of running/blocked/running+blocked processes: "running"/"blocked"/"running+blocked}'; sleep 5; done

 23:45:52 up 52 days,  7:06, 22 users,  load average: 1.40, 1.26, 1.02
Number of running/blocked/running+blocked processes: 3/1/4

 23:45:57 up 52 days,  7:06, 22 users,  load average: 1.45, 1.27, 1.02
Number of running/blocked/running+blocked processes: 2/0/2

 23:46:02 up 52 days,  7:06, 22 users,  load average: 1.41, 1.27, 1.02
Number of running/blocked/running+blocked processes: 1/1/2

 23:46:07 up 52 days,  7:07, 22 users,  load average: 1.46, 1.28, 1.03
Number of running/blocked/running+blocked processes: 2/0/2

 23:46:12 up 52 days,  7:07, 22 users,  load average: 1.42, 1.27, 1.03
Number of running/blocked/running+blocked processes: 2/0/2

 23:46:17 up 52 days,  7:07, 22 users,  load average: 1.55, 1.30, 1.04
Number of running/blocked/running+blocked processes: 2/0/2

 23:46:22 up 52 days,  7:07, 22 users,  load average: 1.51, 1.30, 1.04
Number of running/blocked/running+blocked processes: 1/1/2

 23:46:27 up 52 days,  7:07, 22 users,  load average: 1.55, 1.31, 1.05
Number of running/blocked/running+blocked processes: 2/0/2

 23:46:32 up 52 days,  7:07, 22 users,  load average: 1.62, 1.33, 1.06
Number of running/blocked/running+blocked processes: 2/1/3

 23:46:38 up 52 days,  7:07, 22 users,  load average: 1.81, 1.38, 1.07
Number of running/blocked/running+blocked processes: 1/1/2

 23:46:43 up 52 days,  7:07, 22 users,  load average: 1.66, 1.35, 1.07
Number of running/blocked/running+blocked processes: 1/0/1

 23:46:48 up 52 days,  7:07, 22 users,  load average: 1.53, 1.33, 1.06
Number of running/blocked/running+blocked processes: 1/0/1

Another useful way to typical top output when the load average is high (filter the idle/sleep status tasks with i). So the high load average is because lots of sendmail tasks are in D status. They may be waiting either for I/O or network.

op - 13:23:21 up 329 days,  8:35,  0 users,  load average: 50.13, 13.22, 6.27
Tasks: 437 total,   1 running, 435 sleeping,   0 stopped,   1 zombie
Cpu(s):  0.1%us,  1.5%sy,  0.0%ni, 93.6%id,  4.5%wa,  0.1%hi,  0.2%si,  0.0%st
Mem:  34970576k total, 24700568k used, 10270008k free,  1166628k buffers
Swap:  2096440k total,        0k used,  2096440k free, 11233868k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND            
11975 root      15   0 13036 1356  820 R  0.7  0.0   0:00.66 top                
15915 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15918 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15920 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15921 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15922 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15923 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15924 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15926 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15928 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15929 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15930 root      17   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           
15931 root      18   0  5312  872   80 D  0.0  0.0   0:00.00 sendmail           

References:

  1. What is the relation between I/O wait and load average?

Error “Too many files open” on CentOS 7

If you are encountering Error messages during login with “Too many open files” and the session gets terminated automatically, it is because the open file limit for a user or system exceeds the default setting and  you may wish to change it

@ System Levels

To see the settings for maximum open files,

# cat /proc/sys/fs/file-max
55494980

This value means that the maximum number of files all processes running on the system can open. By default this number will automatically vary according to the amount of RAM in the system. As a rough guideline it will be about 100,000 files per GB of RAM.

 

To override the system wide maximum open files, as edit the /etc/sysctl.conf

# vim /etc/sysctl.conf
 fs.file-max = 80000000

Activate this change to the live system

# sysctl -p

@ User Level

To see the setting for maximum open files for a user

# su - user1
$ ulimit -n
1024

To change the setting, edit the /etc/security/limits.conf

$ vim /etc/security/limits.conf
user - nofile 2048

To change for all users

* - nofile 2048

This set the maximum open files for ALL users to 2048 files. These settings will require a reboot to activate.

References:

  1. How to correct the error “Too many files open” on Red Hat Enterprise Linux

Tools to Show your System Configuration

Tool 1: Display Information about CPU Architecture

[user1@node1 ~]$ lscpu
Architecture: x86_64
CPU op-mode(s): 32-bit, 64-bit
Byte Order: Little Endian
CPU(s): 32
On-line CPU(s) list: 0-31
Thread(s) per core: 2
Core(s) per socket: 8
Socket(s): 2
NUMA node(s): 2
Vendor ID: GenuineIntel
CPU family: 6
Model: 85
Model name: Intel(R) Xeon(R) Gold 6134 CPU @ 3.20GHz
Stepping: 4
CPU MHz: 3200.000
BogoMIPS: 6400.00
Virtualization: VT-x
L1d cache: 32K
L1i cache: 32K
L2 cache: 1024K
L3 cache: 25344K
NUMA node0 CPU(s): 0-7,16-23
NUMA node1 CPU(s): 8-15,24-31
.....
.....

Tool 2: List all PCI devices

[user1@node1 ~]# lspci -t -vv
-+-[0000:d7]-+-00.0-[d8]--
| +-01.0-[d9]--
| +-02.0-[da]--
| +-03.0-[db]--
| +-05.0 Intel Corporation Device 2034
| +-05.2 Intel Corporation Sky Lake-E RAS Configuration Registers
| +-05.4 Intel Corporation Device 2036
| +-0e.0 Intel Corporation Device 2058
| +-0e.1 Intel Corporation Device 2059
| +-0f.0 Intel Corporation Device 2058
| +-0f.1 Intel Corporation Device 2059
| +-10.0 Intel Corporation Device 2058
| +-10.1 Intel Corporation Device 2059
| +-12.0 Intel Corporation Sky Lake-E M3KTI Registers
| +-12.1 Intel Corporation Sky Lake-E M3KTI Registers
| +-12.2 Intel Corporation Sky Lake-E M3KTI Registers
| +-12.4 Intel Corporation Sky Lake-E M3KTI Registers
| +-12.5 Intel Corporation Sky Lake-E M3KTI Registers
| +-15.0 Intel Corporation Sky Lake-E M2PCI Registers
| +-16.0 Intel Corporation Sky Lake-E M2PCI Registers
| +-16.4 Intel Corporation Sky Lake-E M2PCI Registers
| \-17.0 Intel Corporation Sky Lake-E M2PCI Registers
.....
.....

Tool 3: List all PCI devices

[user@node1 ~]# lsblk
sda 8:0 0 1.1T 0 disk
├─sda1 8:1 0 200M 0 part /boot/efi
├─sda2 8:2 0 1G 0 part /boot
└─sda3 8:3 0 1.1T 0 part
├─centos-root 253:0 0 50G 0 lvm /
├─centos-swap 253:1 0 4G 0 lvm [SWAP]
└─centos-home 253:2 0 1T 0 lvm

Tool 4: See flags kernel booted with

[user@node1 ~]
BOOT_IMAGE=/vmlinuz-3.10.0-693.el7.x86_64 root=/dev/mapper/centos-root ro crashkernel=auto rd.lvm.lv=centos/root rd.lvm.lv=centos/swap rhgb quiet LANG=en_US.UTF-8

Tool 5: Display available network interfaces

[root@hpc-gekko1 ~]# ifconfig -a
eno1: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
ether XX:XX:XX:XX:XX:XX txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
.....
.....
.....

Tool 6 Using dmidecode to find hardware information
See Using dmidecode to find hardware information