Linux - Create a service for the new instance - using systemd

How to create a service for the new instance - using systems?

In this example: MySQL service.

1. Create “.service” file
Save in “/lib/systemd/system/” or “/etc/systemd/system”

touch mysql_3307.service
vi mysql_3307.service
 

[Unit]
Description=MySQL 3307 service
After=network.target
 
[Service]
Type=simple
Restart=always
User=mysql
Group=mysql
ExecStart=/etc/mysql/sudo mysqld --defaults-file=/etc/mysql/second_server.cnf
TimeoutSec=600
RuntimeDirectory=mysqld
RuntimeDirectoryMode=755
LimitNOFILE=5000
 
[Install]
WantedBy=multi-user.target

2. Start the service
Sudo systemctl start mysql_3307


3. Checking
systemctl status mysql_3307
 journalctl -xe


* Stop the service (if required)
systemctl stop mysql_3307

Linux: switch user to the root user

 sudo su

Linux – start, stop and check status of a service

Start a service: (in this example, service name is mysql)

Myuser@MyLinuxServer:~$ sudo service mysql start

Myuser@MyLinuxServer:~$

See service status: (in this example, service name is mysql)

Myuser@MyLinuxServer:~$ sudo service mysql status

● mysql.service - MySQL Community Server

   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)

   Active: active (running) since Sun 2020-12-20 15:19:08 UTC; 8s ago

  Process: 8358 ExecStart=/usr/sbin/mysqld --daemonize --pid-file=/run/mysqld/mysqld.pid (code=exited, status=0/SUCCESS)

  Process: 8333 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=0/SUCCESS)

 Main PID: 8360 (mysqld)

    Tasks: 33 (limit: 4915)

   CGroup: /system.slice/mysql.service

           └─8360 /usr/sbin/mysqld --daemonize --pid-file=/run/mysqld/mysqld.pid

Dec 20 15:19:07 MySQL systemd[1]: Starting MySQL Community Server...

Dec 20 15:19:08 MySQL systemd[1]: Started MySQL Community Server.

Myuser@MyLinuxServer:~$

Stop a service: (in this example, service name is mysql)

Myuser@MyLinuxServer:~$ sudo service mysql stop

Myuser@MyLinuxServer:~$

Linux: Create a file

 touch myfile.txt

Linux: The unit file, source configuration file or drop-ins of MYSERVICE.service changed on disk

 An error while trying to start a service:

root@MySQL:/lib/systemd/system# systemctl status MYSERVICE.service

Warning: The unit file, source configuration file or drop-ins of MYSERVICE.service changed on disk. Run 'systemctl daemon-reload' to reload units.

Solution:

As written: run 'systemctl daemon-reload' to reload units.

systemctl daemon-reload

This command is required every time the .service file is changed.

Linux: show enviroment parameter

Show environment parameter <PARAM_NAME> on Linux:

echo $<PARAM_NAME>

example: echo $PATH 

Linux - ubuntu - 'apt-get' is ubuntu 'yum'

 Run: 

sudo yum install openssl

Error:

There are no enabled repos.

 Run "yum repolist all" to see the repos you have.

 You can enable repos with yum-config-manager --enable <repo>

Run successfully:

sudo apt-get install openssl

The usual way to install packages on the command line in Ubuntu is with apt-get.

The usual way to install packages on the command line in Red Hat is with yum.

netstat - network statistics

netstat is a command displays statistics on all network activities.

main options:

-a Displays all active ports

-n Numerical display of addresses and port numbers

-o Displays the process identifiers (PID)

| grep 11753 - displays information only for IP 11753 (or other filter)

netstat -a -n | grep 11753

Stop running command in linux

1. find the PID of the command:
ps -aux | grep -i <PART_OF_THE_COMMAND>

• the second column is the PID

2. kill the command:
kill -TERM <PID>

Linux - make a copy of a file

cp <FILENAME> <path>/<NEWFILENAME>

Connect to isql

isql Uusername Ppassword [Sserver]

(U , P , S - as is and then replace to the user, password, ...)
( Pay attention: names are case-sensitive )

Unix/Linux zip commands

zip file: 
zip FILENAME.ZIP

unzip file: 
unzip FILENAME.ZIP

unzip to a folder: 
unzip FILENAME.ZIP -d FOLDERNAME

instsall zip:
sudo apt install zip

Unix/Linux files commands

remove a file
rm
(rm * - remove all files in the folder)
(-f - force deletion)

find a file in a folder including sub-folders by it's name:
find -name FILENAME
find a file in a folder including sub-folders by part of it's name:
find -name FILEN*

view text of a file
more FILENAME

• Exit by pressing q key

edit a file
vi FILENAME

• To save a file: press Esc key, type :w, Enter
• To save a file and quit: press Esc key, type :x, Enter

grant privilege to a user
chown -R USERNAME: FOLDERNAME
(-R - to recursively operate on all files and directories under the given directory)

Unix/Linux System and enviroment commands

show enviroment parameters
env
show enviroment parameters results match a specified pattern
env | grep STRING

add parameter to env or replace exists value:
export PARAM="VALUE"
concantanete value to exists parameter in env:
export PARAM="VALUE":$PARAM

available and used disk space usage
df
(df -h - more human display)

Unix/Linux basic commands

where I am
pwd

go to FOLDERNAME folder
cd FOLDERNAME

go to parent folder
cd ..

display what is in the folder
ls
(-l all files)
(- la all include hidden)

create a folder
mkdir FOLDERNAME

display an user manual for a command
man COMMAND

switch user
su

run a command like admin (= "as administrator" in windows)
sudo COMMAND ...

desplay results that match a specified pattern
COMMAND | grep STRING

show commands history
history