Linux notes

Useful commands¶

cat {print file to screen}
head {see start of file}
tail {see end of file}
dmesg {system errors/logs}
sudo dmesg -c {clear logs}
sudo raspi-config {configure pi}
clear {clear terminal screen}
sudo lsusb -v {list attached USB devices}
ls -l {long list, provides filesize, etc.}
rm -r {recursive remove, works for directories that aren't empty}
stat /tmp/checkpoint {full date info on file}
df {check space remaining on file systems}
which [command]
Increase screen resolution:
sudo nano /home/pi/.vnc/config then add -geometry 1600x900
sudo apt install guake (then F12 to show/hide console, Ctrl-Shift-T for new tab, Ctrl-Page Up/Page Down to navigate) - https://github.com/Guake/guake/
tar -xzf [filename.tar.gz]
less {excellent way to view a file, H for help, Q to quit, lowercase-G jump to start, uppercase-G jump to end}
env to print environment variables
watch to run a command at pre-defined intervals - e.g., watch -n 5 ls to print the directory listing every 5s. Can set to exit when change detected, etc.

to find recursively in folders...
find . -name '*.xml'
ip a (list ip addresses)

Split commands over multiple lines using \ at the end of the line, just ensure no space to the right of it

Handy command list - https://gist.github.com/tuxfight3r/60051ac67c5f0445efee

Activating RDP¶

If using a distro that doesn't have screen sharing installed by default (on Debian this can simply be enabled via Settings > System > Desktop sharing) then RDP can be enabled using the below commands.

Connecting to a locked session

By default GNOME screen sharing blocks remote access when the screen is locked.

This can be addressed by using the Allow Locked Remote Desktop extension below.

Note this isn't an issue with xrdp however it doesn't allow simultaneous sessions and also blocks access to elevated UI elements (e.g., to change settings).

Install xrdp

sudo apt update
sudo apt install xrdp xorgxrdp
sudo systemctl enable --now xrdp
sudo systemctl enable --now xrdp-sesman
sudo groupadd rdp
sudo usermod -aG rdp youruser
sudo systemctl restart xrdp

Enabling sound on xrdp

To enable RDP sound run the following commands:

sudo apt update
sudo apt install pipewire-module-xrdp
sudo usermod -a -G audio,pipewire $USER

(then reboot - if using Remmina as a client then ensure sound is enabled by editing the connection profile - under Advanced change the Audio output mode to Local)

If wanting to connect via RDP from Linux then Remmina is an excellent client.

GNOME extensions¶

Here are some of the particularly useful extensions I've found.

Allow Locked Remote Desktop¶

This is to allow remote desktop connections when the screen is locked.

GNOME Extensions | GitHub

Clipboard indicator¶

A reliable and feature-rich clipboard manager.

GNOME Extensions | GitHub

Places Status indicator¶

Adds a link to the top-left bar that allows you to quickly jump to folders and network shares. Officially supported by GNOME.

GNOME Extensions | GitLab

Running Citrix¶

Download the client from https://www.citrix.com/downloads/workspace-app/linux/workspace-app-for-linux-latest.html

Download PEM certificate for "DigiCert Global G2 TLS RSA SHA256 2020 CA1" from https://knowledge.digicert.com/general-information/digicert-trusted-root-authority-certificates (direct link https://cacerts.digicert.com/DigiCertGlobalG2TLSRSASHA2562020CA1-1.crt.pem)

Copy it to the Citrix certificate store:

sudo cp ~/Downloads/DigiCertGlobalG2TLSRSASHA2562020CA1-1.crt.pem opt/Citrix/ICAClient/keystore/cacerts

Re-hash the certificate:

sudo /opt/Citrix/ICAClient/util/ctx_rehash

Should then be able to connect OK.

Terminal colours¶

If terminal reverts to non-coloured then try copying skeleton files back again

Restore skeleton files

cd ~
cp /etc/skel/.profile .profile
cp /etc/skel/.bashrc .bashrc

View logs¶

sudo journalctl -u service-name
last -adF logged in user details sudo lastb -adF failed (bad) logins

Easily view large folders¶

Install duc (http://duc.zevv.nl/) - sudo apt install duc -y
sudo duc index / - to index the entire disk (can change to just a subdirectory, which is quicker) sudo duc ui / - to view in an easily navigable form

Remove large docker elements¶

docker image prune
docker system prune -a
(note will need to recreate the mkdocs-checkforupdates container after that)

Log size¶

Find out how much disk space /var/log/journal is consuming with sudo journalctl --disk-usage

Shrink/Reduce the folder size instantly/immediately (e.g. Delete old log files form /var/log/journal folder, reduce the folder size to 500MB)
sudo journalctl --vacuum-size=500M

Control/Limit the disk space /var/log/journal can use by manually editing the configuration file /etc/systemd/journald.conf
sudo nano /etc/systemd/journald.conf

Uncomment the following line in the configuration file and add the desired sized (e.g., 500MB): SystemMaxUse=500M

tldr¶

Useful alternative to man
Install then run update to cache locally.

sudo apt get install tldr && tldr -u

xdg-open¶

Open current folder in graphical explorer

xdg-open .

Can replace the . with another folder name or a URL.

iperf¶

sudo apt install iperf Run server: iperf -s Connect client: iperf -c <ip_of_server>

Bash tips¶

Ctrl-U clear line
Ctrl-L clear screen
Ctrl-R search command history
cd - to switch between directories

Docker tips¶

Attach to running container docker exec -it [container name] sh

command line startup - either pfetch (v compact) or neofetch (bigger but prettier)¶

wget https://github.com/dylanaraps/pfetch/raw/master/pfetch
chmod +x pfetch
sudo cp pfetch /usr/bin/local

sudo nano ~/.bashrc and add pfetch
sudo nano ~/.config/neofetch/config.conf [to uncomment IP addresses]

btop (formerly bpytop)¶

pre-requisite: sudo apt install bzip2 make
go to https://github.com/aristocratos/btop/releases/latest

wget [latest x64 version for Linode, armv7l for Pi]
tar -xjf [filename].tgz
./install.sh

nano¶

Ctrl-Z to background
fg on terminal to then run again
jobs to list currently running background processes

ncdu¶

shows usage by directory
sudo apt instal ncdu
sudo ncdu -x / (to only show files from root but on local filesystem)

glances¶

pip3 install glances
pip3 install bottle
glances -w
http://192.168.2.138:61208/
can also install as a docker container

if lost bash settings¶

cp /etc/skel/.profile ~/
cp /etc/skel/.bashrc ~/
nano .bashrc and force_color_prompt=yes

Bash history¶

https://www.digitalocean.com/community/tutorials/how-to-use-bash-history-commands-and-expansions-on-a-linux-vps space before command to stop it going into history

Bash debugging¶

Start your bash script with bash -x ./script.sh or add in your script set -x to see debug output. https://unix.stackexchange.com/questions/155551/how-to-debug-a-bash-script

export PuTtY settings & sessions¶

regedit /e "%userprofile%\desktop\putty-registry.reg" HKEY_CURRENT_USER\Software\Simontatham

setup SSH keys¶

ssh-keygen -t rsa -b 4096

This creates: id_rsa [private key - to use as identifier on the client when trying to access the host, is in OpenSSH format]
id_rsa.pub [public key - to go into .ssh/authorized_keys file on the host]

cd ~/.ssh
cat id_rsa.pub >> authorized_keys
then move id_rsa to PC

For PuTTY use:
use puttygen (Conversions > Import key > Save private key) to convert this non-.pub file to PuTTY private key format and point to this in Connection > SSH > Auth. Also add username to Connection > Data
https://thepihut.com/blogs/raspberry-pi-tutorials/securely-logging-into-a-raspberry-pi-without-a-password

SSHFS¶

install sshfs and it allows remote directories to be mounted as local directories

upgrading¶

https://www.raspberrypi.org/documentation/raspbian/updating.md
sudo apt dist-upgrade {upgrade to latest version of Raspbian - beware kills wifi}
sudo apt install rpi-update
sudo rpi-update {updates bleeding edge kernel}
uname -r {check kernel version}
https://marcomc.com/2012/09/how-to-fix-regenerate_ssh_host_keys-failed-on-raspbian-for-raspberrypi/ {what to do if SSH fails}

secure SSH access¶

sudo nano /etc/ssh/sshd_config and add PasswordAuthentication no
sudo systemctl restart sshd

Changing desktop https://raspberrypiuser.co.uk/how-to-install-a-new-desktop-environment-using-raspberry-pi-os

Check current path list echo $PATH

Check installed version of a package dpkg-query -l <packagename>

Check available version of a package apt list <packagename>

tmux¶

Good YT video - https://www.youtube.com/watch?v=B-1wGwvUwm8&t=904s reload config - tmux source-file ~/.tmux.config

Hugo¶

hugo server --bind=YOURLINODEPUBLICIP [or replace with FQDN]
-D to allow drafts

Curl¶

Good documentation site re curl: https://everything.curl.dev/