Start a simple http server using python3

This is very simple, because python3 already has a built in module for http server, called http.server. To use this module, run:

$ python3 -m http.server 8000

whereby 8000 is the port you want the http server to run on. To use privileged ports (under 1024) , just append sudo to the above command, like below:

$ sudo python3 -m http.server 80

Once the command run, you can access the current directory via web, like below:



Once done, press Ctrl-c to terminate the server.

Generating ssh key (public and private)

1. Open terminal
2. Run ssh-keygen command
3. When prompted for filename to save, press enter for default location
4. When prompted for passphrase, you can either put in a passphrase (highly recommended), or just leave it empty (not recommended)
5. Your public key is /home/username/.ssh/id_rsa.pub, and your private key is /home/username/.ssh/id_rsa 

Using yum via socks proxy using proxychains

This is useful when you have a CentOS/Redhat server that needs to be updated, but does not have internet connection to get app from the repo. The only requirement is that the server need to be able to ssh into another server that have internet connection. Let's begin.

Download source for proxychain. You can use the server that have internet connection to do this
# wget -c https://github.com/rofl0r/proxychains-ng/archive/master.zip

Transfer the downloaded file into the server without internet, and unzip the file into /usr/local/src
# unzip master.zip -d /usr/local/src

Change directory to /usr/local/src/proxychains-ng-master
# cd /usr/local/src/proxychains-ng-master

Compile, configure and make
# ./configure && make && make install && make install-config

Setup a dynamic socks proxy on port 8888 by ssh'ing into the server that has internet connection:
# ssh foo@server.with.internet -D 8888

Set proxychains to use the dynamic tunnel, by changing the last line of /usr/local/etc/proxychains.conf to "socks4 127.0.0.1 8888"
# tail -1 /usr/local/etc/proxychains.conf 
socks4  127.0.0.1 8888

Open a new terminal, and run yum command with proxychains. You can see that your yum is tunneled via localhost port 8888:
# proxychains4 yum update
[proxychains] config file found: /usr/local/etc/proxychains.conf
[proxychains] preloading /usr/local/lib/libproxychains4.so
[proxychains] DLL init: proxychains-ng 4.12
...

Set up automated mysql/mariadb backup

We are going to use mysqldump for this automated backup exercise.

Create a read only user in mysql to do the backup, in this case, backupuser

# mysql -uroot -p

mysql> grant lock tables, select on *.* to 'backupuser'@'%' identified by 'password_of_your_choice';

Test doing mysqldump using the new user

# mysqldump -ubackupuser -p --all-databases > /tmp/mysql_all_db.sql

If everything is fine, and the mysql_all_db.sql is created successfully, proceed on giving the backupuser passwordless access to mysql. Add below lines to /root/.my.cnf

[mysqldump]

user = backupuser

host = localhost

password = "password_of_your_choice"

Test whether you can still do mysqldump without the -u and -p options

# mysqldump --all-databases > /tmp/mysql_all_db.sql

If everything is running fine, now is the time to add to crontab

# crontab -e

Put below lines to run the mysqldump command at 11 PM every Saturday, and the filename will be datestamped as well

* 23 * * * Sat /usr/bin/mysqldump --all-databases > /backup/mysql_all_db-$(date +%Y-%m-%d).sql

How to install phpmyadmin on Linux Centos 7

ssh into your centos 7 box, using root (assuming your centos box ip is 10.0.0.100)

# ssh root@10.0.0.100

Install apache web server (httpd)

# yum install httpd

Install php, and php-mysql

# yum install php php-myqsl

Start apache webserver

# systemctl start httpd

Install mariadb-server

# yum install mariadb-server

Start mariadb-server

# systemctl start mariadb

Secure mariadb-server installation (will set root password, and secure mariadb-server installation)

# mysql_secure_installation 

Install epel repo (epel stands for extra package for enterprise linux) 

# yum install epel-release 

Install phpmyadmin
# yum install phpmyadmin

Set phpmyadmin to allow ip from local lan (in this case, the local lan ip segment is 10.0.0.0/24), by changing below lines in /etc/httpd/conf.d/phpMyAdmin.conf
# diff -u phpMyAdmin.conf /etc/httpd/conf.d/phpMyAdmin.conf 
--- phpMyAdmin.conf     2017-07-13 19:24:52.310000000 +0800
+++ /etc/httpd/conf.d/phpMyAdmin.conf   2017-07-13 19:15:50.366000000 +0800
@@ -14,7 +14,7 @@
    
      # Apache 2.4
      
-       Require ip 127.0.0.1
+       Require ip 10.0.0
        Require ip ::1
      
    
@@ -22,7 +22,7 @@
      # Apache 2.2
      Order Deny,Allow
      Deny from All
-     Allow from 127.0.0.1
+     Allow from 10.0.0
      Allow from ::1

@@ -31,7 +31,7 @@
    
      # Apache 2.4
      
-       Require ip 127.0.0.1
+       Require ip 10.0.0
        Require ip ::1
      
    
@@ -39,7 +39,7 @@
      # Apache 2.2
      Order Deny,Allow
      Deny from All
-     Allow from 127.0.0.1
+     Allow from 10.0.0
      Allow from ::

Restart httpd

# systemctl restart httpd 

Using your favorite browser, browse to http://10.0.0.100/phpmyadmin, assuming your server ip address is 10.0.0.100 

Login using your mysql root and password, that has been set in mysql_secure_installation step

Done