Linux Tricks Cheatsheet

Password Generators

$ brew install pwgen     # MacOS
$ sudo dnf install pwgen # Fedora
$ pwgen 12
sei9AhPiokai jaezooThahn4 yahghooCh5ha uquiCh7soog0 Pahthe0fe5Ku owaht4xooPhu
eet2eijeeT6E Chie8oz1Enee Piemu7pi1uqu TheebohNg8se eil2AhNeiF2s WueGh8guoxie

$ sudo dnf install apg   # Fedora
$ apg -n 3 -m 12 -M SNCL
|OgFeOcVask6
Aw*SwuKalap7
Nagnec8swif?

$ brew install gpg       # MacOS
$ sudo dnf install gpg   # Fedora
$ gpg --gen-random --armor 1 14
spdhuOS2il2JjhOq2ZU=

`tree` Directory Viewer

nixCraft tree
OSTechNix tree
GeeksForGeeks tree
hier - description of the file system hierarchy

$ brew install tree # MacOS $ sudo dnf install tree # Fedora

$ tree $ tree /path/to/directory $ tree [options] $ tree [options] /path/to/directory

`dnf` Useful Commands

Fedora package installer DNF

$ sudo dnf install httpd                            # install httpd
$ sudo dnf install httpd-manual -y                  # assume yes
$ sudo dnf dnf check-update                         # check for available updates
$ sudo dnf update                                   # updateb installed packages
$ sudo dnf install unbound-1.4.20-28.el7.x86_64.rpm # install local package
$ sudo dnf remove httpd                             # remove package
$ sudo dnf reinstall httpd -y                       # reinstall package
$ sudo dnf search php                               # search for a package
$ sudo dnf provides /etc/httpd/conf/httpd.conf      # which package provides the file
$ sudo dnf info httpd                               #
$ sudo dnf repoquery --list httpd                   # list the files installed
$ sudo dnf history                                  # installation history
$ sudo dnf history info 13                          # what did install 13 do
$ sudo dnf history undo 13 -y                       # undo install 13
$ sudo dnf history redo 13 -y
$ sudo dnf list installed
$ sudo dnf grouplist                                # list which groups are available, installed, not-installed.
$ sudo dnf groupinfo "Web Server"                   # what is installed by this group

Terminal Pagers

Stolen from the Fedora Magazine: 5 cool terminal pages post.

$ more --help                   # trusty original with limited features
$ more <file>                   #
$ more <file1> <file2> <file3>  # ':n' next file, ':p' previous file

$ less --help                   # many features
$ less <file>                   #
$ less <file1> <file2> <file3>  # ':n' next file, ':p' previous file, ':e' new file

$ most --help                   # good for 'wide' files
$ most <file>                   # screens: 'ctl-x 2' split, 'ctl-x 1' close , 'ctl-x o' switch
$ most <file1> <file2> <file3>  # split-screen and ':n' next file, ':p' previous file

$ pspg --help                   # table friendly pager
$ cat t.csv
a;b;c;d;e
1;2;3;4;5
$ cat t.csv | pspg --csv

mysql> pager pspg;              # replace less or more as pager
$ export PAGER=pspg; mycli ...  # MySQL CLI example
$ export PAGER=pspg; pgcli ...  # PostygreSQL CLI example

Cat File Tricks

$ cat -n <filename>                      # adds line number prefix
$ cat -e <filename>                      # shows crlf ending (Unix, DOS, MacOS)
$ cat -n <filename> | head -5            # (beginning) first 5 lines
$ cat -n <filename> | tail -5            # (ending) last 5 lines
$ cat -n <filename> | tail -10 | head -5 # (middle) first 5 of last 10 lines

Grep File Tricks

$ cat flintstones.yaml
---
family: flintstones
members:
  - Name: Fred
    Age: 35
    Gender: male
  - Name: Wilma
    Age: 25
    Gender: female
  - Name: Pebbles
    Age: 1
    Gender: female
  - Name: Dino
    Age: 5
    Gender: male

$ grep Fred flintstones.yaml
  - Name: Fred

$ grep Name flintstones.yaml
  - Name: Fred
  - Name: Wilma
  - Name: Pebbles
  - Name: Dino

$ grep "Name|Age" flintstones.yaml    # no output
$ grep -E "Name|Age" flintstones.yaml # Extended (a.k.a egrep)
  - Name: Fred
    Age: 35
  - Name: Wilma
    Age: 25
  - Name: Pebbles
    Age: 1
  - Name: Dino
    Age: 5

$ grep Age flintstones.yaml -A 1     # one line After match
    Age: 35
    Gender: male
--
    Age: 25
    Gender: female
--
    Age: 1
    Gender: female
--
    Age: 5
    Gender: male

$ grep Age flintstones.yaml -B 1     # one line Before match
  - Name: Fred
    Age: 35
--
  - Name: Wilma
    Age: 25
--
  - Name: Pebbles
    Age: 1
--
  - Name: Dino
    Age: 5

$ grep Age flintstones.yaml -C 1     # one line Context (before/after) match
  - Name: Fred
    Age: 35
    Gender: male
  - Name: Wilma
    Age: 25
    Gender: female
  - Name: Pebbles
    Age: 1
    Gender: female
  - Name: Dino
    Age: 5
    Gender: male

JSON File Tricks

jq is a lightweight command-line JSON processor, similar to sed.
yq is a Python command-line (jq wrapper) YAML/XML/TOML processor.

$ sudo dnf install jq # Fedora
$ brew install jq     # MacOS
$ pip install yq      # Python

# Command Line examples
$ echo '{"fruit":{"name":"apple","color":"green","price":1.20}}' | jq '.' # pretty-print
$ curl http://api.open-notify.org/iss-now.json | jq '.' # pretty-print HTTP response

# Simple JSON file example
$ jq '.' fruit.json
{
    "fruit": {
    "name": "apple",
    "color": "green",
    "price": 1.2
    }
}
$ jq '.' fruit.json                         # pretty-print file
$ jq '.fruit.color' fruit.json              # extract colors
$ jq '.fruit.color,.fruit.price' fruit.json # extract colors and price
$ jq '.fruit | keys' fruit.json             # keys

# JSON array example
$ jq '.' fruits.json
[
  {
    "name": "apple",
    "color": "green",
    "price": 1.2
  },
  {
    "name": "banana",
    "color": "yellow",
    "price": 0.5
  },
  {
    "name": "kiwi",
    "color": "green",
    "price": 1.25
  }
]

$ jq '.' fruits.json           # pretty-print
$ jq '.[] | .name' fruits.json # list all fruits in the array
$ jq '.[].name' fruits.json    # list all fruits in the array
$ jq '.[1]' fruits.json        # array element 1

Gnome Desktop Custom Launcher

Using PyCharm Community Edition as an example, download the PyCharm Community Edition and unpack the tar.gz file into $HOME/Applications

Create the com.jetbrains.pycharm.community.desktop file, modify it as necessary, and then copy it to $HOME/.local/share/applications

$ cat com.jetbrains.pycharm.community.desktop
[Desktop Entry]
Encoding=UTF-8
Name=PyCharm
Exec=/home/<user>/Applications//bin/pycharm.sh
Icon=/home/<user>/Applications/pycharm-community/bin/pycharm.png
Type=Application
Version=2022.2.2
Terminal=false
Categories=Development;

$ cp ./com.jetbrains.pycharm.community.desktop $HOME/.local/share/applications

WSL2 on Windows

Read the prerequisites in, Install Linux on Windows with WSL

Installation can now be done via the Microsoft Store

First enable Windows optional features to run WSL, so the sequence is as follows.

Windows -> Settings -> Optional Features -> More Windows Features
    - [x] Virtual Machine Platform
    - [x] Windows Subsystem for Linux
Reboot
Install WSL from Microsoft Store
Reboot
Install Ubuntu (20.04.6 LTS) from Microsoft Store

Linux Network Tools

Command	Description
ping, ping6	Send ICMP ECHO_REQUEST to network hosts
hping3	TCP/IP equivalent of ping
curl, wget, HTTPie	Access URL meta-data or content
tc	Show / manipulate traffic control settings
dig, nslookup, host, whois	DNS lookup utilities
ssh, scp sftp	Secure client connection and copy
telnet, ftp,	Insecure client connection and copy
rsync	Sophisticated remote/local file-copying
tcpdump, wireshark, tshark	Dump and analyze network traffic
ngrep	Network grep
ifconfig, route, ethtool, ip	Show/manipulate ip routing, devices, and tunnels
iw, iwconfig	Configure a wireless network interface
nmap, zenmap	Network exploration tool and security/port scanner
p0f	Identify remote systems passively
openvpn, wireguard stunnel	Secure VPN tunnels
nc, socat	Arbitrary TCP and UDP connections and listeners
netstat, ss, lsof, fuser	Troubleshoot connections, processes, file usage
iptables, ip6tables, nftables	Firewall, TCP/IP packet filtering and NAT
arp, arptables,	Manipulate the system ARP cache
traceroute, mtr, tcptraceroute	Troubleshoot connections, processes, file usage
iptraf, nethogs, iftop, ntop	Troubleshoot network bandwidth issues
ab, nload, iperf	Benchmarking tools
ipcalc	Simple manipulation of IP addresses
nsenter	Enter container process’s namespace
Python HTTP modules	HTTP serve files in CWD, `python -m http.server`

Brendan Gregg’s Homepage

G’Day. I use this site to share and bookmark various things, mostly my work with computers. While I currently work on large scale cloud computing performance at Intel (previously Netflix), this site reflects my own opinions and work from over the years. I have a personal blog, and I’m also on twitter.

This page lists everything: Documentation, Videos, Software, Misc. For a short selection of most popular content, see my Overview page.

Managing `.rc` files

Managing dotfiles with rcm on Fedora

By default, rcm uses ~/.dotfiles for storing all the dotfiles it manages.

A managed dotfile is actually stored inside ~/.dotfiles, and a symlinked.

For example, if ~/.bashrc is tracked by rcm, a long listing would look like this.

$ ls -l ~/.bashrc
lrwxrwxrwx. 1 link link 27 Dec 16 05:19 .bashrc -> /home/geoff/.dotfiles/bashrc

rcm consists of 4 commands:

mkrc – convert a file into a dotfile managed by rcm
lsrc – list files managed by rcm
rcup – synchronize dotfiles managed by rcm
rcdn – remove all the symlinks managed by rcm

Fedora 36 Live CD install

Of course backup everything you want to keep because you are going to reformat the HDD or SSD!

The live installation is process is well documented and robust so simply follow:

Next add the RPM Fusion repositories, by installing and configuring them as described in RPMFusion Configuration

Finally consult Fedora Quick Docs especially the Adding and managing software section.

Some of the perennial audio and video playback issues are still there, so follow these instructions.

Installing plugins for playing movies and music

$ sudo dnf install gstreamer1-plugins-{bad-\*,good-\*,base} gstreamer1-plugin-openh264 gstreamer1-libav --exclude=gstreamer1-plugins-bad-free-devel
$ sudo dnf install lame\* --exclude=lame-devel
$ sudo dnf group upgrade --with-optional Multimedia