Linux on Simplestory

Using g++ and gdb

Fri, 02 Mar 2018 00:00:00 +0000

G++ is the C++ compiler under Unix/Linux, and gdb is a powerful debugging tool under Unix/Linux. Most of the time, the C/C++ code we write does not run on Windows but on a Linux system. Here I record some usage of g++ and gdb in case they are needed.

Using g++

When g++ performs compilation work, it needs 4 steps in total:

Preprocessing, generating a .i file, mainly expanding header files and macro definitions: g++ -E test.cpp -o test.i
Compilation, converting the preprocessed file into assembly language and generating a .s file: g++ -S test.i -o test.s
Assembly, turning the assembly into object code (machine code) and generating a .o file, mainly converting the .s file into a binary file: g++ -c test.s -o test.o
Linking, linking the object code to generate an executable program: g++ test.o -o test

The steps above can also be done with a single command:

Configuring Django on Ubuntu

Mon, 19 Feb 2018 00:00:00 +0000

At the time of the 2018 Spring Festival, heaven knows what I went through, posting a blog article on the fourth day of the new year. Django was actually configured before the New Year; I had just learned some knowledge about developing web applications with python at that time, so I configured it along the way.

Environment used for the configuration

System: Ubuntu16.04 (LTS)
python version: python3.6 (using Anaconda to create a virtual environment)

Preparation

Uninstalling an old version of Django

If you are upgrading from an older version of Django, you need to deal with the old version a little.

Configuring Tensorflow on Linux

Sun, 04 Feb 2018 00:00:00 +0000

Borrowing a line from the TensorFlow Chinese community: TensorFlow, an open-source magic tool for artificial intelligence.

Environment used for the configuration

System: Ubuntu16.04 (LTS)
python version: python3.6 (using Anaconda to create a virtual environment)
Nvidia card: Geforce 920M (if there is no Nvidia card, only the CPU version can be installed)

Installing Tensorflow

tensorflow has two versions, CPU and GPU; I created two python virtual environments and installed these two versions separately. Below I record this painful installation process

Linux Penetration Testing Commands

Sat, 20 Jan 2018 00:00:00 +0000

Below is a penetration testing memo for Linux machines; I came across it on the internet by chance and copied it over here.

Penetration testing a Linux machine

Command	Description
netstat -tulpn	Show network ports in Linux together with the corresponding ID (PID)
watch ss -stplu	Observe TCP and UDP ports in real time through sockets
lsof -i	Show established connections
macchanger -m MACADDR INTR	Change the MAC address on KALI Linux
ifconfig eth0 192.168.2.1/24	Set the IP address in Linux
ifconfig eth0:192.168.2.3/24	Add an IP address to an existing network interface in Linux
ifconfig eth0 hw ether MAC ADDR	Change the address in Linux using ifconfig
ifconfig eth0 mtu 1500	Change the MTU size with ifconfig; change 1500 to the MTU you want
dig -x 192.168.1.1	Perform a reverse lookup on an IP address
host 192.168.1.1	Perform a reverse lookup on an IP address; useful when dig is not installed
dig @192.168.2.2 domain.com -t AXFR	Perform a DNS zone transfer with dig
host -l domain.com nameserver	Perform a DNS zone transfer with host
nbtstat -A x.x.x.x	Obtain the domain name corresponding to an IP address
ip addr add 192.168.2.22/24 dev eth0	Add a hidden IP address that does not show up when running ifconfig
tcpkill -9 host goole.com	Block access to goole.com from the host
echo "1">/proc/sys/net/ipv4/ip_forward	Enable IP forwarding, turning the Linux box into a router — which makes it convenient to control the traffic routed through this box
echo "8.8.8.8">/etc/resolv.conf	Use Goole's DNS

System information commands

Very helpful for local enumeration

MySQL Data File Paths on Linux

Fri, 01 Dec 2017 00:00:00 +0000

Server version: 5.7.20-0ubuntu0.16.04.1 (Ubuntu)

After logging into MySQL, you can use the following command to query where the related files are stored:

show variables like '%dir%';

The output is shown below:

Usually these are:

The default location of the database files is: /usr/share/mysql/ Configuration file: /etc/mysql/my.cnf

Database directory: /var/lib/mysql Configuration directory: /etc/share/mysql (mysql.server command and configuration files) MySQL related commands: /usr/bin Startup scripts: /etc/init.d/

One way to start mysql safely: /usr/bin/mysqld_safe-user=root&

Some Linux Commands

Tue, 07 Nov 2017 00:00:00 +0000

Some little-known Linux commands

Installing OpenCV on Linux

Fri, 20 Oct 2017 00:00:00 +0000

Recently, because a project needed computer vision recognition, I started tinkering with OpenCV. Although the installation process was long and winding, the experience of using it together with Python is actually quite good. Here I record the OpenCV installation and compilation process.

System environment: Ubuntu16.04

Software installed: OpenCV3.3.0+Python2.7.12

Updating the system packages:

$ sudo apt update
$ sudo apt upgrade

Installing some developer tools:

$ sudo apt-get install build-essential cmake pkg-config

The pkg-config package is very likely already installed by default, but just in case, add it in as well. The cmake program is used later to compile OpenCV.