Yuol-DevOps-Linux

This a Devops system for Linux Servers of Yangtze University Online, I'm the Author of this System.

This system is based on bash.

Following is note of this repo.

1. My meaning is that the scripts can automatically run in bash with Service crond.

2. There will be help of crond & permissions.

3. And all of the code you can modify & use them as you wish.

4. Following are my plans:

• backup som important files & folders
• Run a check to check the Performance of your servers or vitrual machines
• Create a trash bin on the linux
• ~~etc...~~~

5. Some help of Permissions...

You should give the Permission X to scripts before using them.

As well konwn, everything is file in the linux, and all of files have three basic permissions, there is the list of them.

Read -> r -> 4

Write -> w -> 2

Excution -> x -> 1

In fact, these numbers are Octal, so we can write them as (0421)_o or (0421)₈.

How to view the permissions of files?

In the linux, we can run command ls -l in the bash, and we can see Following Output.

ls -l

-rw-r--r-- 1 user usergroup 0 Mar 22 23:05 example.txt

You can see the infomation of this file called example.txt, and the beginning of the output line is permission of this file. That means the Root user can read & write this file, but the Root UserGroup and the others only can read it, and no one can run it.

if we replace the letters to numbers, it should be -42-4--4--(the first "-" is not useful for us now, we get the permission from the second letter), but we still have a simple way to express it.

these are numbers, so we can add up them, and this permission can be expressed as 644, the rule is as Following:

above all, the command ls -l tell us the owner and the owner group are whom.

if the owner has this permission, the sum = 0 + permission1 + permission2 + permission3, if owner has permission as rwx, the sum = 4 + 2 + 1 =7, other calculating is similar to owner.

so the permission of example.txt can be 644.

But How to Change the Permission?

Run command chmod.

for example, if we want to Change permission,we can run these command.

If you want to change permission to -rwxr-xr-x,you can use chmod 755 files.

we use 755 for files and 644 for folders, if you want to change permission of folder and files in it, you can use this command chmod 755 -R folder .

If you think these ways aren't useful for you, you can use Google or Baidu to search with keyword "change permission".

This help is over.

6. Some help of Crond...

if your server had installed the service crond, look at Following Information
In the bash, you can exec some commands to view, modify even delete the crontab tasks, following are the Commands

crontab -l is to list all crantab tasks
crontab -u root -l is to view tasks of User root. If you want to modify and delete tasks, use this command crontab -e or crontab -u root -e
After using this command, you will get a interface that is alike to Vim, in fact, This is Vim, you can use it to modify your tasks.
You can get some information like following.

* * * * * Some Commands...

The first * is meaning minutes, and following is help of it.

you can use it as a number(0<*<59), that means a firm minute in an hour
you can also use it as (*/15), that means executing Command once every 15 minutes.

as well as, other * have same usage.

and from left to right, they mean that minutes, hours, days, months and weeks.
This is an example. */15 * 25 * * Exec command...

That means every 15 minutes exec minutes run command in 25th every months Help is over, if you need more help, please use Google or Baidu.
https://www.google.com
https://www.baidu.com

Copyright © 2017 Yangtze University Online Stark-Zhang All Rights Reserved

About Author: Stark Zhang, a member of YUOL in 2015, in charge of the Linux servers of Yangtze University yicheng2623825899@gmail.com