2arunpmohan

A systemd component called journald collects and manages journal entries from all parts of the system. This is basically log information from applications and the kernel.

**1. To see all log entries, starting at the oldest entry**

`journalctl`

**2. journal entries from the current boot**

`journalctl -b`

2arunpmohan

**1. start a service**

`sudo systemctl start nginx.service`

**2. Stop a service**

`sudo systemctl stop nginx.service`

**3.Restart a service**

2arunpmohan

the below command will open up the 9100 port.

sudo iptables -I INPUT -p tcp --dport 9100 -jACCEPT

This wont work with AWS

2arunpmohan

create dump files

mysqldump -u root -p test_arun > /home/user/Desktop/test_arun_dump.sql

Restore dump files

mysql -u root -p test_arun_restored < test_arun_dump.sql

for this, we need to create the database "test_arun_restored" prior to to the ececution of the command

2arunpmohan

Size of all the directories, files etc in the current directory in human-readable format.

du -sh *

command to know the free space in the disk:

df -h .

https://unix.stackexchange.com/a/185777

2arunpmohan

Kibana Script usage

How to show the data on Y-axis in percentage

Use case example.

What we want to achieve?
Suppose we want to show the usage statistics of a process in Kibana.
The Y axis -  being the usage of the RAM
and the x-axis - the date/time

2arunpmohan

For that first get the process id (pid) from the below command

        ps aux | grep logstash

After the collection of pid (suppose the pid = 6666) from above, use that like below to get the start time

        ps -eo pid,cmd,lstart | grep 6666

2arunpmohan

#!/bin/bash

if [ -z $1 ] ; then
    echo "Please enter hostname"
    exit
fi

hostname=$1

curl -XDELETE "http://$hostname:9200/suggest-simple"

2arunpmohan

#!/bin/bash

if [ -z $1 ] ; then
    echo "Please enter hostname"
    exit
fi

hostname=$1

curl -XDELETE "http://$hostname:9175/pdf-attachment-04"

2arunpmohan

#To know the ports and process utilisations																									
sudo netstat -ntlp