linux swap memory limits – reference guide

Table 1: Recommended system swap space in Fedora 28 documentation

Amount of system RAMRecommended swap spaceRecommended swap with hibernation
less than 2 GB2 times the amount of RAM3 times the amount of RAM
2 GB – 8 GBEqual to the amount of RAM2 times
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How to use HiDPI(4K) resolution in Linux for all applications

HiDPI (High Dots Per Inch) displays, also known by Apple’s “Retina Display” marketing name, are screens with a high resolution in a relatively small format. They are mostly found in high-end laptops and monitors.

update this

~/.Xresources

Xft.dpi: 240

reboot or re-login to system

*240 dpi is suitable for 3840x2160 
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How To Redirect www to non-www OR non-www to www with Apache

1. Configure DNS Records

In order to set up the desired redirect, www.example.com to example.com or vice versa, you must have an A record for each name.

2. Enable the mod_rewrite module

 a2enmod rewrite

3.1 Update site.conf or .htaccess file ( www to non-www)

RewriteEngine on
RewriteCond %{HTTP_HOST} ^www.yoursite.com 
RewriteRule 
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Testing IPSEC VPN Systems with ike-scan

ike-scan is a command-line tool for discovering, fingerprinting and testing IPsec VPN systems. It constructs and sends IKE Phase-1 packets to the specified hosts, and displays any responses that are received.

ike-scan does two things:

  1. Discovery: Determine which hosts are running IKE. This is done by displaying those hosts which
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iptables explained

iptables

Iptables is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel. Several different tables may be defined. Each table contains a number of built-in chains and may also contain user-defined chains.

Each chain is a list of rules which can match … Read more

The new architecture for the Windows Subsystem for Linux: WSL 2!

wsl2

Changes in this new architecture will allow for: dramatic file system performance increases, and full system call compatibility, meaning you can run more Linux apps in WSL 2 such as Docker.

WSL 2 is a new version of the architecture that powers the Windows Subsystem for Linux to run ELF64 … Read more