Linux notes

Linux Notes.md

Authorized keys

mkdir -m 700 /root/.ssh
echo "my public key" > /root/.ssh/authorized_keys
chmod 600 /root/.ssh/authorized_keys
restorecon -r /root/.ssh

source: https://www.centos.org/forums/viewtopic.php?t=2480

Create an HTTP proxy over SSH

# Create a socks proxy to remote server
ssh -D 1080 -C -q -N <remote>
# Create an http proxy over socks
polipo socksParentProxy=localhost:1080
# Test the HTTP proxy
http_proxy=localhost:8123 curl http://ifconfig.co

As a result, we've two proxy servers running on localhost:

SOCKS 5 proxy localhost:1080

HTTP proxy localhost:8123

convert between SSH2 and OpenSSH

Needs OpenSSH to be installed on the system

SSH2 to OpenSSH

ssh-keygen -i -f /path/to/Identity.pub > ~/.ssh/id_rsa.pub

OpenSSH to SSH2

ssh-keygen -e -f /path/to/id_rsa.pub > /path/to/Identity.pub

sudoers

Allow <user> to run a bash script as "root" without password

<user>	ALL=(root) NOPASSWD: /path/to/script

pay attention to <tab> after <user>

Swap

# List configured swap files
swapon -s

# Disable all swapfiles
swapoff -a

# Create a 1GB empty file
dd if=/dev/zero of=/swapfile bs=1M count=1024

# Make that empty file a swapfile
mkswap /swapfile

# Enable swapfile for system to use
swapon /swapfile

Random Password

LC_CTYPE=C tr -dc A-Za-z0-9 < /dev/urandom | head -c${1:-32};echo

Create User

useradd -d /home/user -m -s /bin/bash user
passwd user

Disable or change user shell

# disable
chsh -s /bin/false user
# change
chsh -s /bin/zsh user

Set defult locale

printf \
"export LANGUAGE=en_US.UTF-8\n\
export LANG=en_US.UTF-8\n\
export LC_ALL=en_US.UTF-8\n" \
>> /etc/environment

~/.ssh/config

Host vagrant
	HostName vagrant.local
	User ubuntu
	Port 2222
	IdentityFile /Users/refik/Sites/vagrant/xenial/.vagrant/machines/web/virtualbox/private_key
  

simple-nodejs-nginx.conf

upstream app {
    server 127.0.0.1:3001;
    keepalive 8;
}


server {
  
	  listen 80 default_server;
	  listen [::]:80 default_server;
  
    server_name _;
  
    server_tokens off;

    location / {
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header Host $http_host;
        proxy_set_header X-NginX-Proxy true;

        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";

        proxy_pass http://app/;
        proxy_redirect off;
    }
}