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Linux

Terminal-first guides, real shell scripts, and field notes from years of sysadmin work.

140 articlesWritten by Ishan Karunaratne
Linux sysadmin guides on bash, shell scripts, find, grep, ssh, and terminal-first workflows.
Why find scripts break between macOS and Linux: -printf and -regextype are GNU only, regex flavors and stat format strings differ. The portable find subset, the gotchas, and brew install findutils for gfind.
FeaturedLinux

BSD find vs GNU find: Every macOS vs Linux Difference That Matters

macOS ships BSD find; Linux ships GNU find. The two share a name and most of an interface, but -printf, -regextype, and the stat format strings diverge hard enough to break scripts shipped between platforms. The full divergence list, the portable subset that works on both, and how to get GNU find on a Mac.

More in Linux
The grep -o | sort | uniq -c | sort -rn pipeline counts unique matches and ranks them. Why sort comes before uniq, worked log-analysis examples, sort -u, uniq -d, and the awk one-pass alternative.
Linux

How to Count Unique Matches with grep, sort, and uniq

The grep -o 'pattern' file | sort | uniq -c | sort -rn pipeline is the classic log-analysis one-liner. Why sort must come before uniq, how each stage works, worked examples for top IPs and status codes, the awk one-pass alternative for huge files, and the BSD vs GNU notes.

find walks the live filesystem every time; locate and plocate query a prebuilt updatedb database. Compare freshness, speed, permission-awareness, and filtering, plus the mlocate vs plocate split and the macOS mdfind alternative.
Linux

find vs locate vs mlocate: Which File Search Tool to Use

find walks the live filesystem every time it runs: always current, sometimes slow. locate queries a prebuilt database: instant, but stale until the next updatedb. This breaks down the locate family (mlocate, plocate, slocate), the macOS situation, and exactly when to reach for each one.

Use grep 'pattern' file | awk '{print $2}' to filter lines and print a specific column. awk field basics, custom separators with -F, multi-column output, grep -o and cut alternatives, and when awk alone replaces the pipe.
Linux

How to grep and Print a Specific Column (grep + awk)

grep filters lines, awk extracts fields. The classic pipe is grep 'pattern' file | awk '{print $2}'. This covers awk field basics ($1, $NF), custom separators with -F, multi-column output, the cases grep -o and cut cover on their own, and the fact that awk's own pattern match makes the grep half optional.

rsync files modified in the last N days by piping find -print0 into rsync --files-from=- --from0. The relative-path gotcha, the dry run, BSD vs GNU notes, and when rsync filters replace find.
Linux

How to rsync Only the Files find Selected

rsync has no native time filter, so the standard trick is to let find pick the files and feed the list to rsync. The one-liner is find ... -print0 | rsync --files-from=- --from0, and the failure mode is always the same: the paths in the list have to be relative to the rsync source argument. The breakdown, the dry run habit, and when rsync's own filters make find unnecessary.

Archive every file matching a find pattern with tar. The safe find -print0 | tar --null --files-from=- one-liner, the macOS BSD tar -T difference, archiving by modification time, and gzip vs bzip2 vs xz vs zstd.
Linux

How to Archive Files Matching a find Pattern with tar

find locates the files, tar archives them. The safe pairing is find -print0 piped into tar reading a NUL-delimited list from stdin: no breakage on spaces or newlines. The flag breakdown, the macOS BSD tar vs GNU tar difference, the -exec append alternative, archiving by modification time, and the compression choices.

grep is universal and searches everything you point it at; ripgrep (rg) is the fast Rust default that skips .gitignore'd and binary files; ag is the older fast-grep now superseded. Compare speed, defaults, and regex engines.
Linux

grep vs ripgrep vs ag: Which Search Tool to Use

grep is on every system and searches exactly what you point it at. ripgrep (rg) is the fast Rust-based default for code search: it skips .gitignore'd, hidden, and binary files unless told otherwise. ag (the_silver_searcher) was the older fast-grep, now largely superseded by ripgrep. This breaks down speed, defaults, regex engines, and exactly when to reach for each one.

Use xargs -P to run find results in parallel: find ... -print0 | xargs -0 -P 4 -n 1 cmd. Set -P to the core count, why -n 1 matters, CPU-bound vs IO-bound work, and xargs -P vs GNU parallel.
Linux

How to Run find in Parallel with xargs -P

find . -type f -name '*.log' -print0 | xargs -0 -P 4 -n 1 gzip compresses every matched file four at a time. The flags that make it work: -P for parallel workers, -n 1 so each worker gets one job, -0 paired with find's -print0 for safety. When parallelism helps (CPU-bound work) and when it just thrashes the disk.

find -name uses shell globs on the basename; find -regex matches a full regular expression against the whole path. The -regextype flavors, the GNU emacs vs BSD basic default drift, and when each one is the right tool.
Linux

find -regex vs -name: When to Use Regex in find

find -name takes a shell glob and matches the basename; find -regex takes a full regular expression and matches the whole path. That whole-path detail is the number one surprise: -regex '.*\.txt' works but -regex '.txt' matches nothing. The flag reference, -regextype flavors, the GNU vs BSD default-flavor drift, and when -name is the better tool.

Skip node_modules, .git, and build output from grep with --exclude-dir, exclude filename globs with --exclude, and search only matching files with --include. The one-liner, brace expansion, --exclude-from, and the BSD grep fallback.
Linux

How to Exclude Files and Directories from grep

grep does not read .gitignore, so skipping node_modules, .git, and build output is on you. The flags that do it: --exclude for filename globs, --exclude-dir for whole directories, --include for the inverse, --exclude-from to read the list from a file, plus the find -prune fallback for older macOS grep.

Exclude a directory in find with -path './node_modules' -prune -o ... -print. Why the trailing -print is mandatory, the multi-directory form, the slower -not -path alternative, and BSD vs GNU notes.
Linux

How to Exclude a Directory in find (the -prune Pattern Explained)

find -path './node_modules' -prune -o -type f -print skips a directory subtree instead of walking into it. The pattern looks strange because -prune is an action, not a test, and the trailing -print is mandatory once you write an explicit action. The breakdown, the multi-directory form, the slower -not -path alternative, and when each one is the right call.

Use grep -l 'pattern' files to list only the filenames that contain a match. The inverted grep -L, the recursive grep -rl one-liner, the NUL-safe xargs pipeline for find-and-replace, and the macOS BSD vs GNU notes.
Linux

How to List Only Filenames with grep -l

grep -l prints the name of each file that contains a match and stops reading at the first hit, which makes it the fast answer to 'which files contain this string'. The lowercase -l, the inverted -L for files missing a pattern, the grep -rl one-liner, the NUL-safe xargs pipeline for find-and-replace, and the BSD vs GNU notes.

Rank the biggest files on a full disk with find -printf '%s %p' piped to sort -rn. The GNU one-liner, the BSD stat variant for macOS, why -xdev matters, human-readable sizes, and when du or ncdu beats find.
Linux

How to Find the Largest Files on Disk (find, sort, du)

find / -xdev -type f -printf '%s %p\n' | sort -rn | head -20 gives you a ranked list of the biggest files on a full disk. The GNU one-liner, the BSD/macOS stat variant, why -xdev matters, human-readable output with numfmt, when to switch to du or ncdu for per-directory totals, and the mistakes that send a scan into /proc.

grep -E vs grep -P explained: basic regex (BRE) treats + ? | ( ) { } as literal text, extended regex (ERE) makes them metacharacters, and PCRE adds lookaround and \d. Plus why macOS BSD grep has no -P.
Linux

grep Regex: BRE vs ERE vs PCRE Explained

grep has three regex engines and the default one surprises everyone: in basic regex (BRE) the characters + ? | ( ) { } are literal text until you backslash-escape them. -E switches to extended regex (ERE) where they work bare, and -P unlocks Perl-compatible regex with lookaround and \d. The full BRE vs ERE vs PCRE comparison, the same pattern in all three, and why -P does not exist on macOS.

Use find -user, -group, and -perm to locate files by ownership and mode. The -perm -mode vs -perm /mode distinction explained, world-writable and SUID/SGID audit recipes, orphaned-file checks, and the BSD vs GNU find differences on macOS.
Linux

How to Find Files by Owner, Group, or Permission with find

find -user www-data lists every file owned by a user; -group developers filters by group; -perm matches the mode bits. The subtle part is -perm -mode (all of these bits set) versus -perm /mode (any of these bits set). Plus the security-audit recipes for world-writable files and SUID/SGID binaries, the BSD vs GNU divergences, and the orphaned-file checks.

Use grep -w to match a whole word instead of a substring. What grep counts as a word boundary, the \b and \< \> regex equivalents, -x for whole-line match, and BSD vs GNU differences.
Linux

How to Match a Whole Word with grep -w

grep cat also matches category, concatenate, and scatter. grep -w cat matches only the standalone word. The whole-word flag, what grep counts as a word boundary, the regex equivalents with \b and \< \>, the stricter -x whole-line cousin, and the BSD vs GNU differences that bite on macOS.

Use find ... -print0 | xargs -0 grep -l 'PATTERN' to find every file containing a string. When grep -r is enough, when to add find as a pre-filter for performance, multi-pattern matching with -E, and the safe NUL-delimited pipeline.
Linux

How to Find Files Containing Specific Text (find + grep)

find ... -print0 | xargs -0 grep -l 'PATTERN' finds every file containing a piece of text. The combo handles weird filenames, scales to huge trees, and replaces three other common but broken pipelines. When to use grep -r alone, when to add find as a pre-filter, and the BSD vs GNU pitfalls.

Use find -type d -empty to list empty directories and find -type f -empty for empty files. The -depth trap for deleting nested empty trees, the hidden-file gotcha, the safe two-pass cleanup, and BSD vs GNU find notes.
Linux

How to Find (and Delete) Empty Directories and Files

find . -type d -empty lists every empty directory; find . -type f -empty lists every empty file. The catch is what 'empty' means (a hidden file makes a directory not empty) and the -depth trap that lets find -delete collapse whole nested empty trees in one pass. The flag reference, the safe two-pass cleanup, the BSD vs GNU notes, and the mistakes that bite.

Search multiple patterns with grep: grep -e 'A' -e 'B', grep -E 'A|B' alternation, and grep -f patterns.txt. Covers -F fixed strings, AND logic with chained greps and PCRE lookahead, and BSD vs GNU differences on macOS.
Linux

How to Search Multiple Patterns with grep

grep can OR several patterns three ways: -e per pattern, -E with alternation, or -f reading the list from a file. The one-liner is grep -E 'ERROR|WARN|FATAL' file. Here is when to pick each, how -F speeds up literal multi-pattern search, why grep has no single-pass AND, and the BSD vs GNU differences that bite on macOS.

Use grep -C 3 'pattern' file to print 3 lines before and after each match. The -A, -B, -C context flags, the -- group separator, asymmetric context, recursive search, and BSD vs GNU grep differences.
Linux

How to Show Lines Before and After a grep Match (Context)

grep -C 3 'pattern' file prints the matching line plus 3 lines on each side. The three context flags (-A after, -B before, -C both), how the -- group separator works between match blocks, asymmetric context, recursive context search, and the macOS BSD vs GNU differences that bite.

find -exec ... {} + batches arguments into one command (fast). find ... -exec ... {} \; forks per file (slow). xargs adds shell flexibility but needs -0 for safety. The decision matrix and performance comparison.
Linux

find -exec vs xargs: Which to Use (and the {} + Trick That Beats Both)

find -exec ... {} + and find -print0 | xargs -0 are roughly equivalent for batch operations on matched files. find -exec ... {} \; forks once per match and is much slower. The decision matrix: when -exec is enough, when xargs adds value, and the safety rules for filenames with spaces, newlines, and quotes.

grep -c counts matching lines, not occurrences. Use grep -o piped into wc -l for the true count, grep -rc for per-file counts, grep -vc to count non-matching lines, plus the macOS BSD vs GNU differences.
Linux

How to Count Matches with grep -c (and the Line-vs-Occurrence Trap)

grep -c counts matching LINES, not occurrences. A line with three hits still counts as 1. The fix is grep -o piped into wc -l, which puts every match on its own line first. Per-file counts, filtering out the :0 noise, counting non-matching lines, and the BSD vs GNU differences.

Use find -type f -name '*.txt' for one extension, or group -name tests in escaped parens joined by -o for many (.jpg, .png, .gif). Case-insensitive -iname, files with no extension, the -regex shortcut, and BSD vs GNU find differences.
Linux

How to Find Files by Extension (One or Many) with find

find . -type f -name '*.txt' lists every file with one extension. For many extensions you group -name tests with escaped parens and join them with -o. This covers the single one-liner, the multi-extension OR pattern, why the parens are mandatory, case-insensitive -iname, files with no extension at all, the -regex shortcut, and the BSD vs GNU divergence that bites on macOS.

find -delete removes every matched file with no confirmation. The safe -print-first dry-run pattern, depth-first directory deletion, when to use -exec rm vs xargs rm -f, and the BSD vs GNU differences.
Linux

How to Find and Delete Files Safely with find -delete

find -delete removes every matched file with no confirmation and no undo. The safe pattern is to write the command with -print first, eyeball the list, then swap -print for -delete. Plus the directory-depth-first trap, when to use -exec rm instead, and the find -delete vs xargs rm -f tradeoff.

How to grep case-insensitively with grep -i. Combine -i with -r, -w, -v, -c, the locale caveat for non-ASCII case folding, the PCRE (?i) inline flag, and BSD vs GNU grep differences.
Linux

How to grep Case-Insensitively (grep -i)

grep -i 'pattern' file matches regardless of case. The flag pairs with -r, -w, -v, and -c the way you would expect, but -i only folds ASCII case reliably. Non-ASCII case folding (accented characters, the Turkish dotted-i) depends on your locale. The combinations, the locale caveat, the PCRE per-pattern (?i) flag, and the BSD vs GNU differences.

Use find -size +100M to list files larger than 100 megabytes. Unit suffixes (c/k/M/G), +/- sign convention, combine with sort -rn to surface the biggest files on disk, and BSD vs GNU rendering differences.
Linux

How to Find Files Larger Than a Size with find -size

find . -size +100M lists every file larger than 100 megabytes. The unit suffixes (c, k, M, G), the +/- sign convention, how to combine with sort to find the biggest files on disk, the BSD vs GNU divergence for printing sizes, and the wc -c trick for byte-exact thresholds.

Use grep -v 'pattern' file to print every line that does not match. Exclude multiple patterns with -e or -vE, strip comments and blank lines, count with -vc, and avoid the OR-becomes-AND double-negative trap.
Linux

How to Exclude Matches with grep -v (Invert Match)

grep -v 'pattern' file prints every line that does NOT match. The flag reference, how to exclude multiple patterns, the strip-comments-and-blank-lines pipeline, the double-negative trap where -v of an OR becomes an AND of negations, and the macOS BSD vs GNU differences.

Use find -mtime -7 to list files modified in the last 7 days. The off-by-one (-7 means under 7 days, +7 means over 7 days), -mmin for minute resolution, -newer for exact timestamps, and the BSD rounding gotcha on macOS.
Linux

How to Find Files Modified in the Last 7 Days (find -mtime)

find -mtime -7 lists every file modified in the last 7 days. The catch is the off-by-one: -7 means less than 7 days ago, +7 means more than 7 days ago, and exact-7 almost never matches what people expect. The flag reference, worked variations for hours and minutes, the BSD vs GNU rounding difference, and the safe cleanup patterns.

Use grep -r 'pattern' . to search every file in a directory tree. The -r vs -R symlink difference, --include and --exclude-dir filters, -rl and -rn, and the macOS BSD vs GNU grep gaps.
Linux

How to grep Recursively Through a Directory

grep -r 'pattern' . searches every file under a directory tree. The catch is the path argument people forget, the -r vs -R symlink difference, and the unfiltered crawl into node_modules and .git. The flag reference, the --include and --exclude-dir filters, the macOS BSD vs GNU gaps, and when to reach for ripgrep or git grep instead.

Download a Facebook video from the command line with yt-dlp: public watch and fb.watch links work without cookies, private and group videos use Firefox cookies, and you choose the resolution.
Linux

How to Download a Facebook Video with yt-dlp

Download a Facebook video free from the command line with yt-dlp: public watch links and fb.watch shorts need no cookies, private and group videos use --cookies-from-browser firefox, and you pick the resolution yourself.

Download an Instagram Reel or video from the command line with yt-dlp using browser cookies, covering reels, feed videos, IGTV, and audio-only.
Linux

How to Download an Instagram Reel or Video with yt-dlp

Download an Instagram Reel or video free from the command line with yt-dlp. Instagram needs you logged in, so cookies are mandatory: how to pass them, keep them fresh, and grab reels, feed videos, IGTV, or just the audio.

Download all TikTok videos from a user with yt-dlp: point it at the profile URL, pass Firefox cookies for the full listing, and use a download archive for resumable backups.
Linux

Download Every Video From a TikTok Profile with yt-dlp

Download all TikTok videos from a user free with yt-dlp: point it at the profile URL, pass browser cookies (TikTok needs them for the full listing), and use a download archive so re-runs only grab new clips. The natural way to back up your own TikTok.

Download a TikTok video free with yt-dlp from the command line: pull the source MP4, follow short links, extract audio, and use cookies for gated or region-locked clips.
Linux

How to Download a TikTok Video with yt-dlp

Download a TikTok video free from the command line with yt-dlp: no app, no sketchy site. yt-dlp pulls the source MP4 TikTok serves, follows short links, extracts audio, and uses your cookies for gated clips.

Download an entire YouTube playlist or channel free with yt-dlp: use a download archive for incremental re-runs, organize files with output templates, grab item ranges, and rate-limit big channels.
Linux

Download a YouTube Playlist or Entire Channel with yt-dlp

Download a whole YouTube playlist or entire channel free with yt-dlp: point it at a playlist or @handle, use a download archive so re-runs skip what you already have, organize files with output templates, and rate-limit to dodge the bot wall.

duf is a df replacement that prints grouped, color-coded disk usage tables. Install it, filter local devices with --only local, sort by --sort usage, hide mounts with --hide-mp, and emit --json for scripts.
Linux

duf: A Friendlier df for Disk Usage

duf is a df replacement that prints grouped, color-coded disk usage tables instead of df's raw columns. Install it, filter to the devices you care about, sort by usage, and pipe --json into scripts.

Combine animated GIFs into one from the command line with gifsicle: merging is the default mode for sequential playback, set the loop count, match sizes, and work around the 256-color limit.
Linux

How to Combine Animated GIFs Into One With gifsicle

Combine animated GIFs into one from the command line with gifsicle. Merging is the default mode, the loop quirk that makes it look broken, plus matching sizes, the 256-color ceiling, and the ffmpeg alternative.

Normalize MP3 and audio volume from the command line with ffmpeg loudnorm (EBU R128 LUFS) and rsgain ReplayGain tagging across a library.
Linux

How to Normalize Audio Volume From the Command Line

Normalize MP3 and audio volume from the command line: ffmpeg's loudnorm filter for EBU R128 loudness (one-pass and the accurate two-pass), rsgain for ReplayGain tags across a whole library, and why loudness beats peak normalization.

nvtop gpu monitoring on Linux: an htop-style ncurses viewer for NVIDIA, AMD, and Intel GPUs showing live utilization, VRAM, temperature, and a sortable per-process list. Install, key bindings, and -d delay flag.
Linux

nvtop: Monitor NVIDIA, AMD, and Intel GPUs on Linux

nvtop is an htop-style GPU monitor for Linux. One install (sudo apt install nvtop), one command, and you get live per-GPU utilization, memory, temperature, and a sortable per-process list across NVIDIA, AMD, and Intel cards.

Convert a PSD to PNG from the command line with ImageMagick using the [0] composite-layer trick, extract individual layers, batch a folder, and the Maximize Compatibility caveat.
Linux

How to Convert a PSD to PNG From the Command Line

Convert a PSD to PNG from the command line with ImageMagick. The one trick that matters: design.psd[0] selects the flattened composite, so you get one PNG instead of a folder full of separate layers.

Turn Bluetooth on or off from the macOS terminal with blueutil: power toggle, read state, list paired devices, and connect by address.
Linux

How to Turn Bluetooth On or Off From the macOS Command Line

Toggle Bluetooth on or off from the macOS terminal with blueutil: blueutil -p 1 / -p 0 / -p toggle, read the current state, list paired devices, and connect or disconnect by address. The reliable route now that Apple removed the old defaults hacks.

bat is a cat command replacement with syntax highlighting, line numbers, and Git change markers. Install it, alias cat with --paging=never, and use --plain, --style, --paging, and --diff in scripts and pipes.
Linux

bat: A cat Clone With Syntax Highlighting

bat is a cat command replacement that adds syntax highlighting, line numbers, and Git change markers. Install it, alias cat to it carefully, and know the --plain, --style, --paging, and --diff flags that make it behave well in scripts and pipes.

Reverse a video from the command line with ffmpeg: the reverse video filter, the areverse audio filter, and the new-output-file rule that keeps the source intact.
Linux

How to Reverse a Video with ffmpeg

Reverse a video with ffmpeg using the reverse filter for picture and areverse for sound. Why you must write to a new output file, and why you trim before you reverse.

exa and eza are modern ls replacements for the terminal: colorized output, a built-in git status column, tree view with -T, icons, and a long-listing that beats ls -l. eza is the maintained fork to install now that exa is unmaintained.
Linux

exa and eza: A Modern ls Replacement

exa was the modern ls replacement with color, a git column, and a tree view in one binary; it is now unmaintained and eza is the drop-in fork to install instead. The flags, the eza migration, and when plain ls is still the right call.

Convert WebM to MP4 with ffmpeg, re-encode VP9 and Opus into H.264 and AAC, fix the QuickTime black screen with yuv420p, and convert back to WebM with VP9 and Opus.
Linux

How to Convert WebM to MP4 (and Back) with ffmpeg

Convert WebM to MP4 with ffmpeg: why it has to re-encode (VP9/Opus into H.264/AAC, not a stream copy), the yuv420p flag that fixes the QuickTime black screen, and the reverse MP4 to WebM with VP9 and Opus.

Enable TCP BBR congestion control on Linux with net.ipv4.tcp_congestion_control=bbr and net.core.default_qdisc=fq. The kernel version that ships BBR, the fq qdisc it needs, throughput gains on lossy links, and BBR vs CUBIC.
Network

Speed Up a Linux Server With TCP BBR

Switch to TCP BBR congestion control with two sysctl lines and a reboot-safe config file. The throughput it buys you on lossy long-haul links, the fq qdisc it needs, the kernel version that ships it, and when CUBIC is still the right default.

Speed up or slow down a video with ffmpeg using the setpts video filter and the atempo audio filter, including the atempo 0.5 to 100 range and why you still chain it in steps of 2.0 for larger factors.
Linux

How to Speed Up or Slow Down a Video with ffmpeg

Change a video's speed from the command line with ffmpeg: setpts for the video, atempo for the audio, why you still chain atempo in steps of 2.0 even though it now accepts up to 100, and keeping both tracks in sync.

Run sudo iftop -i eth0 to see bandwidth per connection in real time. The interface flag, -n and -P for readable output, the 2s/10s/40s rate columns, BPF filter syntax, and how iftop differs from nload.
Linux

iftop: See Bandwidth by Connection in Real Time

sudo iftop -i eth0 shows a live, per-connection bandwidth table: which host pairs are moving traffic and at what rate. The interface flag people forget, the -n and -P switches that make the output readable, the 2s/10s/40s columns, the filter syntax, and when nload or iftop is the right tool.

ShellCheck tutorial: install the shell script linter, run it on a Bash file, read SC2086 and other SC codes, suppress findings with disable directives, and add it to CI.
Linux

ShellCheck: Catch Bash Bugs Before They Bite

ShellCheck is a static analysis linter for Bash and POSIX sh: install it, run it on a script, read the SC codes, suppress false positives with disable directives, and wire it into CI.

ffmpeg cheat sheet: -c copy stream copy, -ss/-to/-t trim, scale and crop filters, -vn audio extract, palettegen/paletteuse for high-quality GIFs, libx264/libx265/libsvtav1 with -crf and -preset, setpts and atempo speed, concat demuxer, subtitles, and common-error fixes.
Linux

The ffmpeg Command Cheat Sheet

A scannable ffmpeg reference: convert containers, stream-copy without re-encoding, trim and cut, resize and crop, extract or replace audio, high-quality GIFs with palettegen, x264/x265/AV1 quality with -crf and -preset, change speed, concat, subtitles, and the fixes for the errors you actually hit.

Why SSH reports REMOTE HOST IDENTIFICATION HAS CHANGED, when it is safe, and how to clear the stale known_hosts entry with ssh-keygen -R.
Linux

Fix SSH "Host Key Verification Failed"

Why SSH warns that the remote host identification has changed, when it is safe to clear, and the one command that removes the stale known_hosts entry: ssh-keygen -R.

The nload command shows live network bandwidth per interface in the terminal. Install nload, switch interfaces with arrow keys, read In/Out/Avg/Max, plus -m multi-view, -u unit flags, and the refresh interval.
Linux

nload: Watch Live Network Bandwidth in the Terminal

The nload command draws a live graph of incoming and outgoing bandwidth per interface, right in the terminal. Install it, run nload, switch interfaces with the arrow keys, and read the In/Out, Avg, and Max numbers. The -m multi-interface view, the -u/-U unit flags, the refresh interval, and where iftop and nmap fit instead.

Crop a video with ffmpeg using the crop filter: width:height:x:y from the top-left origin, centered and square crops with in_w/in_h, and cropdetect for black bars.
Linux

How to Crop a Video with ffmpeg

Crop a video with ffmpeg's crop filter: crop=w:h:x:y from the top-left origin, centered crops with in_w/in_h expressions, square crops for social, and cropdetect to strip black bars automatically.

Disable direct root login over SSH and the console, lock the root password, and use a normal account plus sudo instead, safely.
Linux

How to Disable Root Login on Linux

Disable direct root login over SSH and on the console, lock the root password, and move everyone to a normal account plus sudo, without locking yourself out.

jpegoptim CLI usage: lossless and lossy modes, --max quality, --strip-all metadata removal, bulk find + xargs -P parallel pipelines, comparisons with mozjpeg, squoosh-cli, and sharp-cli.
Linux

How to Optimize JPEG Images Using jpegoptim

Use jpegoptim to losslessly or lossy-compress JPEGs from the command line, in bulk, and inside CI pipelines. Includes the install path on macOS/Linux/Windows, mozjpeg / squoosh-cli / sharp comparisons, and the parallel xargs pattern for tens of thousands of images.

Verify a file's SHA-256 checksum on macOS with shasum -a 256, check it against a published hash with -c, and pick the right algorithm in 2026.
Linux

How to Verify a File Checksum on macOS (SHA-256)

Verify a file's SHA-256 checksum on macOS from the command line: compute it with shasum -a 256, check it against a published hash with -c, and know why SHA-256 (not MD5 or SHA-1) is the right choice in 2026.

How to schedule a cron job on Linux: edit your crontab, write the five-field cron schedule, and point it at a command to run on a recurring timer.
Linux

How to Schedule a Cron Job on Linux

Schedule a recurring task on Linux with cron: open your crontab, write the five-field schedule, point it at a command, and avoid the environment and day-of-week traps that make jobs run at the wrong time.

Why SSH rejects your key with Permission denied (publickey) and the ordered checklist that fixes it: agent, identity file, server authorized_keys, and permissions.
Linux

Fix SSH "Permission denied (publickey)"

The ordered checklist for SSH Permission denied (publickey): is the key loaded, is it the right key, is the public half on the server, and are the server-side permissions sane.

Create a hardware-backed SSH key on a YubiKey with ssh-keygen -t ed25519-sk. How FIDO2/U2F SSH keys work, ed25519-sk vs ecdsa-sk, resident keys, and the OpenSSH and firmware versions you need.
Security

SSH Keys With a YubiKey (FIDO2 / U2F)

Generate a hardware-backed SSH key on a YubiKey with one ssh-keygen command. How FIDO2/U2F SSH keys work, the difference between ed25519-sk and ecdsa-sk, resident keys, and the firmware and OpenSSH versions you need.

Trim or cut a video from the command line with ffmpeg using -ss and -to or -t, the fast lossless stream-copy way and the frame-accurate re-encode.
Linux

How to Trim or Cut a Video with ffmpeg

Trim or cut a video from the command line with ffmpeg: the fast lossless -c copy way, the keyframe gotcha that makes your cut land early, and the frame-accurate re-encode. With -ss and -to/-t explained.

Bind separate SSH keys to separate hosts in ~/.ssh/config with IdentityFile and IdentitiesOnly so the correct key is offered every time.
Linux

Use Multiple SSH Keys with ~/.ssh/config

Run separate SSH keys for work, personal, and GitHub by binding each to its host in ~/.ssh/config with IdentityFile and IdentitiesOnly, so the right key is always offered.

Extract audio from a video with ffmpeg by copying the stream untouched (fast, lossless) or re-encoding to MP3, AAC, or WAV when you need a different format.
Linux

How to Extract Audio From a Video with ffmpeg

Pull the audio out of a video with ffmpeg: copy the stream untouched when you just want to demux (fast, lossless), or re-encode to MP3, AAC, or WAV when you need a different format. Plus how to check the source codec first and grab a single segment.

which vs type vs command -v compared: which is a non-standard external program, command -v is the POSIX way to resolve a command path in scripts, and type reports aliases, functions, and builtins.
Linux

which vs type vs command -v: Find a Command Path

which vs type vs command -v for finding where a command lives: which is an external program with portability problems, command -v is the POSIX-standard choice for scripts, and type tells you the most.

LUKS disk encryption with cryptsetup on Linux: luksFormat to encrypt a block device, luksOpen to unlock it, then mkfs and mount. Includes header backup and keyslot management.
Security

LUKS Disk Encryption With cryptsetup

Set up LUKS disk encryption with cryptsetup: format a block device, open it, put a filesystem on it, and mount it. The four commands, plus the header backup nobody warns you about.

Bash job control reference: Ctrl-Z to suspend, fg and bg to resume, jobs to list, kill %1 by job spec, and nohup, disown, and setsid to survive logout.
Linux

Bash Job Control: fg, bg, jobs, and nohup

Bash job control reference: suspend with Ctrl-Z, resume in foreground with fg or background with bg, list with jobs, target jobs by %1/%+/%-, and keep a process alive past logout with nohup, disown, or setsid.

Generate an SSH key with ssh-keygen: pick Ed25519 over RSA, decide on a passphrase, and set the ~/.ssh permissions SSH needs. Linux, macOS and Windows.
Linux

How to Create an SSH Key in 2026

Create an SSH key in one ssh-keygen command. Which key type to pick in 2026 (Ed25519 vs RSA), whether to set a passphrase, and the file permissions SSH needs, on Linux, macOS and Windows.

List all Linux users and groups from /etc/passwd and /etc/group with getent, and tell human accounts from system accounts by UID.
Linux

How to List Users and Groups on Linux

List every user and group from /etc/passwd and /etc/group with getent, tell human accounts from system ones by UID, and see which groups a user belongs to.