Tuesday, 27 August 2019

Ansible Commands Book

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-> valid syntax of the playbook $ ansible-playbook -i myhosts example.yml -v  -- syntax-check -> show elapsed time of the playbook $ ...

How to drop database/user on logical replicated database?

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1st step on 2nd node: $ echo "DROP SUBSCRIPTION exampledb_node_2" | psql on 1st node: $ echo "DROP PUBLICATION exampledb...
Saturday, 29 June 2019

Kubernetes label usage

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e.g. namespace; kube-system -> List labels # kubectl get pods --all-namespaces --show-labels # kubectl get pods -n kube-system -...
Sunday, 19 May 2019

Examples of "escape sequences" usage on echo command

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To use interpretation of backslash escapes, just need to put " -e " parameters afterward echo command. Info: " -e " me...
Friday, 22 February 2019

Linux Terminal Commands Book

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*  chage (manage user password settings) *  hostnamectl   (show hostname settings) *  date  (manage system date and time) * rpm   (means ...
Thursday, 3 January 2019

How to fix "connection refused" error?

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Error e.g. The connection to the server 10.10.10.10:6443 was refused - did you specify the right host or port? Solution On kubernetes ...
Wednesday, 19 December 2018

What are the differences of su/ su -/ sudo / sudo su in linux system?

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Info:  su means, switch user or substitute user sudo means, super user do to use sudo command, related user must be defined in sudoers fi...
Thursday, 1 November 2018

How to change timezone?

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-> Determine your timezone # cd /usr/share/zoneinfo # tzselect e.g. Europe/Istanbul -> Remove current localtime soft link # rm ...
Wednesday, 31 October 2018

How to connect into local VM via SSH?

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* Set a new Port Forwarding Rule in Network Settings Step 1: Settings -> Network -> Adapter 1 -> Advanced -> Adapter Type -...

WSREP "Failed to open channel" solution

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Error ERROR WSREP "Failed to open channel 'my_mariadb_cluster'" Detailed Error WSREP: gcs/src/gcs.cpp:gcs_open():1458:...
Monday, 8 October 2018

How to find/follow postgresql server logs?

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-> Check log level from config file # cat /var/lib/pgsql/data/postgresql.conf e.g. log_min_messages= 'ERROR' (default value) ...
Thursday, 4 October 2018

How to setup/configure/use mailx for Office365 account?

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-> Update the OS # yum -y update or (y -> yes) # yum update -> Install mailx # yum install -y mailx -> Define soft link ...

How to solve "restarting/pending pod repeatedly" problem?

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-> Check the pods status e.g. # kubectl get pods --all-namespaces NAMESPACE     NAME                            READY     STATUS kube...
Tuesday, 2 October 2018

How to enable Hyper-V in Windows 10?

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Press Windows key -> Type "Turn Windows features on or off" then click it -> Select " Hyper-V" check box then c...
Tuesday, 18 September 2018

How to install/configure/enable NTP service?

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-> Install ntp service # yum install ntp -> Once NTP server  pool zones are taking e.g. check from  https://www.pool.ntp.org/zone...
Thursday, 9 August 2018

How to check linux operating system info?

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-> show kernel version and other info # uname -a -> show machine info #  hostnamectl -> show specific release version # rpm -...

How to check available yum packages?

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e.g. install/update ansible by yum -> Go to repo path # cd /etc/yum.repos.d/ -> Add source paths into repo file to be able to ins...

How to install/configure/run ansible?

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-> Set hostname # hostnamectl set-hostname ansible_host -> Add remote hosts into /etc/hosts file # vi /etc/hosts 10.10.10.2 remo...
Tuesday, 7 August 2018

usage of "run_once: true" option

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If you want to run only once a specific task during all playbook execution, you may add " run_once: true " option into your task t...
Monday, 30 July 2018

How to know last login info on the system?

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-> show all records $ last -> show all records page by page $ last | more -> show first 10 records $ last | head -> sho...