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Technical Notes

These notes are my personal online notebook of useful commands and "how-to's". You are welcome to make use of them if you find them helpful. They obviously don't come with any warranty! Click on one of the category tags above for the notes in any category.

ubuntu packages can be upgraded. Run apt list --upgradable

apt list --upgradable

Then (if desired) they can be upgraded one at a time with:

apt install --only-upgrade [packagename]

Unsnap Firefox

Five Steps

sudo snap remove firefox

sudo add-apt-repository ppa:mozillateam/ppa

echo '
Package: *
Pin: release o=LP-PPA-mozillateam
Pin-Priority: 1001
' | sudo tee /etc/apt/preferences.d/mozilla-firefox

echo 'Unattended-Upgrade::Allowed-Origins:: "LP-PPA-mozillateam:${distro_codename}";' | sudo tee /etc/apt/apt.conf.d/51unattended-upgrades-firefox

sudo apt install -y --allow-downgrades firefox
sudo dpkg-reconfigure unattended-upgrades    #And answer NO

Repairing grub boot in EFI system running Ubuntu

sudo fdisk -l
#now identify EFI and linux partitions and set them here

sudo apt -y install grub-efi
sudo mkdir /media/root && sudo mount $LIN /media/root
sudo mkdir /media/efi && sudo mount $EFI /media/efi
sudo grub-install --target=x86_64-efi $EFI --efi-directory=/media/efi --boot-directory=/media/root/boot


Preventing false mouse double-clicks under linux

Newer versions of Kubuntu are missing the advanced mouse options which let you debounce the mouse

sudo apt install xserver-xorg-input-evdev
sudo mkdir -p /etc/X11/xorg.conf.d

Then edit /etc/X11/xorg.conf.d/xorg.conf

and append:

Section "InputClass"
    Identifier "evdev-mouse"
    MatchIsPointer "yes"
    Driver "evdev"

You may have to reboot at this point


Fixing a Linux broken boot

If the system has been corrupted, and there is no grub menu, then boot from a live CD, open a terminal and do this:


Compress a folder into a single file for backup

tar -cvjSf filename.tar.bz2 foldername
-c create
-v verboase
-j bzip2
-S Sparse files handled efficiently
-f filename


Wiping a Hard Drive Clean

To securely wipe a hard drive of all data, do:

apt install wipe
shred -vfz -n 2 /dev/sdb
  • Options above are verbose, force, zero out in an extra pass
  • Number of passes: -n 2

An alternative “light” way of doing this is to simply copy random bytes


iptables configuration on a linux server

  • List current tables with line numbers and stats
iptables -L INPUT --line-numbers -v
  • Append another rule
iptables -A INPUT -s -j DROP
  • Delete rule #3
iptables -D INPUT 3
  • The moment you apply IPTABLE rule it immediately becomes active.But it will not survive a reboot.
  • To be able to survive IPTABLES a reboot in your network configuration file /etc/network/interfaces file (referring to a Debian/Ubuntu system) you need to add:


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