Tips Linux

Linux, DevOps and Security

Author: matthieu

Elegant way to pass arguments to a bash script

 

When I started to write bash scripts, I found that it was really convenient to use the basic way to pass arguments with $1 $2 and so on.

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Root password Linux reset in 1 minute

This little trick recently saved me from a critical situation and shows one more time the weakness of every system with unencrypted disks.

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Reverse shell on firewalled server

Sometimes, it may be useful to keep a connection to a server (let’s call it SERVER_1) that is not reachable from the internet because of iptables ingress rules or simply because it doesn’t have a public IP.  You can reach it from another server (let’s name it SERVER_2) that is accessible.

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Simple python random

Recently, I had to chose randomly 4 people for a thankless task. It was the perfect occasion to code a simple script using the Python random module:
#!/usr/bin/python
# -*- coding: utf-8 -*-
#export PYTHONIOENCODING=utf8
import random
people_initials = ['ML','WD','ME','BH','FS','AQ','SB','FR','KB','LL','FP','MG','AH','FJ']
rand_people = random.sample(people_initials, 4)
print rand_people

 

Don’t name your script random.py or it won’t work.

Vim – Find and replace strings

Vim can be hard to use at the beginning, but when you’re used to it and know a few tricks, it’s impossible to go back to nano, also known as ‘the text editor for kids’.

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Shell script to add keys to ssh config file

When you have many servers with different usernames, keys etc, it’s easier to manage the server with the .ssh/config file.

A very basic script that I wrote long time ago to easily add an host to my ~/.ssh/config file.

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How to resume a stalled scp transfer

SCP is the perfect command line tool to transfer huge files from a server to another one but if the connection drops, the transfer become “stalled” and seems impossible to resume. Don’t panic, rsync allow us to resume a failed scp transfer :

 

rsync --partial --progress --rsh=ssh user@server:path/my_file /home/my_file

 

A quick and dirty method to launch one or more scripts as daemon with nohup

A quick and dirty method to launch one or more scripts as daemons with nohup :
nohup python3 myscript.py

You can safely close the terminal and your script will continue to operate in background.

IP extraction

Regex are useful to cope with basic unix / linux administration tasks.
To extract IP from file, this simple command do the trick :
grep -o '[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}\.[0-9]\{1,3\}' /var/log/auth.log 15-08-27 - 16:17:00
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
188.216.199.96
188.216.199.96
188.216.199.96
188.216.199.96
188.216.199.96
188.216.199.96
188.216.199.96
188.216.199.96
188.216.199.96
188.216.199.96
188.216.199.96
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142
11.213.54.142

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