#!/bin/bash

## remswap.sh
## version 1.0
## Quickly deactivate and remove a SWAP file.

## Author: Ze'ev Schurmann
## License: GPL3.0 or later
## Git Repo: https://git.zaks.web.za/thisiszeev/linux-server-tools

## Usage:
##
## (as root)
##   ./remswap.sh {/swapfile.0xx}
##
## (with sudo)
##   sudo ./remswap.sh {/swapfile.0xx}
##
## {/swapfile.0xx} is optional. The 0xx extension is a range of numbers from 001 to
## 024. If you leave it out then the last file in the sequence will be removed.
##
## The script will quickly deactivate a SWAP file, removed it and remove it from
## /etc/fstab
##
## It is important that you have addswap.sh and remswap.sh in the same folder and
## set the permissions to 700 and the owner and group to root. Do not try and run
## either script with out root or sudo privelages.
##
## A log file can be found at /var/log/swapmanagement.log

## Why did I make these two scripts?
##
## I use Debian as my daily driver (I've been using Linux in some for or the other
## as my daily driver since 2006). I also us Debian for all my servers. I also
## running a webhosting business (https://www.zaks.web.za) and in my 20+ years in
## the game, I have learned that... 1. VPS's do not come with SWAP, but sometimes
## you need a bit of SWAP to handle heavy load. 2. SWAP files can be added and
## removed on the fly (no reboot required), however a SWAP partition, not so simple.
##
## On my daily driver machine, I also create a lot of digital artwork. I recently
## found myself rendering a finished artfile that was 9.5GB (24000px by 13700px)
## in Gimp, and half way through I started running out of RAM and SWAP. So I
## quickly created the needed SWAP file, and Gimp was able to finish the render
## without crashing.

## Plans for the future:
##
## I am planning to make a configurable service file that can be run in the
## background to automatically create more SWAP files when your server/computer is
## under load, and remove excess SWAP files when the server/computer is no longer
## under load.

## Do you have a script idea?

## If you have an idea for a useful server script for selfhost/homelab environments,
## please start a chat with me on Reddit /u/thisiszeev and share your idea. I might
## just make it a reality, and give you credit in the relevant README.md file.

## Donations
##
## Please consider making me small donation. Even though my scripts are open source
## and free to use, I still need to eat. And the occasional bottle of wine also goes
## down well.
##
##     $5 buys me a cup of coffee
##     $10 buys me a nice burger
##     $20 buys me a bottle of wine
##     Anything above that will be awesome as well.
##
## You can send me a donation via Paypal https://www.paypal.com/paypalme/thisiszeev
##
## Drop me a message on Reddit if you do make a donation. u/thisiszeev
##
## Support is only offered freely to those who donate $20 or more.
##
## Your donation contributes to further development.
##
## If you need a custom script, contact me on Reddit for pricing.

function echolog {
  echo "$1"
  echo "$(date) > remswap > $1" >> /var/log/swapmanagement.log

  if [[ $(wc -l < /var/log/swapmanagement.log) -gt 300 ]]; then

    cat /var/log/swapmanagement.log | tail -n 250 > /var/log/swapmanagement.temp && mv /var/log/swapmanagement.temp /var/log/swapmanagement.log

  fi
}

if [[ -z $1 ]] || [[ $1 == "" ]]; then

  swapfile=$(ls -1 /swapfile.* 2>/dev/null | tail -1)

  if [[ -z "$swapfile" ]]; then

    echolog "No swap files found to remove."
    exit 1

  fi

elif [[ $1 =~ ^/swapfile\.0(0[0-9]|1[0-9]|2[0-4])$ ]] && [[ -f $1 ]]; then

  swapfile="$1"

else

  echolog "Invalid swap file name given or swap file does not exist."
  exit 2

fi

if swapon --show=NAME | grep -qF "$swapfile"; then

  echolog "Turning off $swapfile..."
  swapoff "$swapfile"

else

  echolog "$swapfile is not active."

fi

if grep -Fq "$swapfile" /etc/fstab; then

  echolog "Removing $swapfile entry from /etc/fstab..."
  sed -i "\|$swapfile|d" /etc/fstab

else

  echolog "$swapfile entry not found in /etc/fstab."

fi

echolog "Deleting $swapfile..."
rm -f "$swapfile"

if [[ $? == 0 ]]; then

  echolog "$swapfile successfully removed."
  partitioncount=$(swapon --show | grep "partition" | wc -l)
  filecount=$(swapon --show | grep "file" | wc -l)
  echolog "You now have $partitioncount active swap partitions and $filecount active swap files."
  exit 0

else

  echolog "$swapfile failed to be removed."
  exit 3

fi