Cheat sheet
/dev/null, /dev/zero and /dev/urandom cheat sheet
What Linux's special files do and how to use them: discard output, make test and swap files, wipe disks, generate random data and secrets, and test disk speed.
// cheat sheet
Cheat sheets
Compact, regularly updated references for the tools I use every day.
Cheat sheet
Ansible cheat sheet
Ad-hoc commands, inventories, playbook flags, check and diff mode, tags, limits and Vault: the Ansible commands I run every day.
Cheat sheet
apt vs dnf cheat sheet
The same package tasks side by side on Debian/Ubuntu (apt, dpkg) and RHEL, Rocky and Fedora (dnf, rpm): install, search, hold, history and repos.
Cheat sheet
awk cheat sheet
Split, filter, sum and reformat columns with awk: fields, separators, conditions and the one-liners I use on logs and command output.
Cheat sheet
Bash scripting cheat sheet
Write Bash scripts that fail loudly and clean up after themselves: strict mode, quoting, tests, loops, arrays, functions, traps and getopts.
Cheat sheet
cron cheat sheet
Schedule jobs with cron: the five-field syntax, special strings, where crontabs live, the environment trap, logging, locking and one-off jobs with at.
Cheat sheet
crontab and /etc/cron.* cheat sheet
Where cron jobs live on Linux: user crontabs, /etc/crontab, /etc/cron.d and the cron.hourly, daily, weekly and monthly folders, run-parts naming rules and anacron.
Cheat sheet
curl cheat sheet
HTTP from the terminal with curl: headers, methods, JSON APIs, auth, downloads, TLS checks and timing a request phase by phase.
Cheat sheet
Disk full cheat sheet
Why a Linux disk says it's full and how to fix it: find what uses the space, free space held by deleted files that are still open, and fix running out of inodes.
Cheat sheet
find cheat sheet
Find files by name, type, size, age and permissions, and act on them safely with -exec, -delete and xargs.
Cheat sheet
grep cheat sheet
Search text and logs with grep: the flags for context, recursion, regular expressions and counting, plus when to reach for ripgrep.
Cheat sheet
head and tail cheat sheet
Show the first or last lines or bytes of a file, follow logs that rotate, skip headers and cut out a range of lines with head and tail.
