htop – A Comprehensive User‑Guide

1. What is htop?

htop is an interactive, colour‑enhanced alternative to the classic top command. It provides a real‑time view of system processes, CPU/memory usage, and load averages, while allowing mouse interaction and on‑the‑fly configuration changes.

Key benefits over top:

2. Installation

htop is available in the repositories of virtually every Linux distribution. Choose the method that matches your OS.

2.1 Debian / Ubuntu / derivatives

sudo apt update
sudo apt install htop

Tip: On Ubuntu 22.04+ the package name is still htop. No extra repos required.

2.2 Red Hat / CentOS / Fedora

# RHEL / CentOS 7 (EPEL repo)
sudo yum install epel-release
sudo yum install htop

# RHEL / CentOS 8 / Rocky / AlmaLinux (dnf)
sudo dnf install htop

# Fedora (latest)
sudo dnf install htop

2.3 Arch Linux & Manjaro

sudo pacman -Syu htop

2.4 macOS (Homebrew)

brew install htop
# On macOS you may need to grant permissions for htop to read process info:
sudo chmod +s $(which htop)   # optional, see the caveats printed by brew

2.5 Building from source

If you need the absolute latest version or want to compile with custom options:

# Prerequisites
sudo apt install libncursesw5-dev build-essential git   # Debian/Ubuntu
# Or: sudo dnf install ncurses-devel gcc make git

# Clone repo
git clone https://github.com/htop-dev/htop.git
cd htop

# Build
./autogen.sh && ./configure && make

# Install (optional, requires root)
sudo make install

The binary will be installed as /usr/local/bin/htop.

3. Starting htop

htop

• Run as normal user – you’ll see only processes you’re allowed to see.
• Run as root (sudo htop) – you get a full system view, and you can send signals to any process.

Additional command‑line options (see man htop for the complete list):

Example:

htop -d 0.5 -u root -s PERCENT_CPU

4. Understanding the Interface

When htop launches, the screen is divided into three main areas.

4.1 Header (Meters)

  1  [||||||||||||||||||||||||||||||||||||||||||||||||||||||||]  0.0%
  2  [||||||||||||||||||||||||||||||||||||||||||||||||||||||||]  0.0%
  3  [||||||||||||||||||||||||||||||||||||||||||||||||||||||||]  0.0%
  4  [||||||||||||||||||||||||||||||||||||||||||||||||||||||||]  0.0%
  Mem[|||||||||||||||||||||||||||||||||||||||]  2.31/7.79 GiB
  Swp[|||||||||||||]  0.00/2.00 GiB
  Load average: 0.15 0.07 0.03

• CPU meters: one per core (or combined if you select “CPU” as a single meter).
• Memory / Swap: visual bars with absolute usage shown.
• Load average: 1‑, 5‑, 15‑minute system load.

You can toggle which meters appear via F2 → Setup.

4.2 Process List (Columns)

You can add or remove columns in the Setup menu (F2 → Columns) or via the F keys (see below).

4.3 Footer (Key hints)

At the bottom you’ll see a concise list of the most used keys, for example:

F1 Help  F2 Setup  F3 Search  F4 Filter  F5 Tree  F6 SortBy  F7 Nice-  F8 Nice+  F9 Kill  F10 Quit

These are always available, no matter which screen you are on.

5. Basic Navigation & Keyboard Shortcuts

Most of these keys work with the mouse as well: clicking column headers sorts, clicking a process selects it, right‑click opens a context menu (if compiled with mouse support).

6. Customising the Display

htop is designed to be tweaked on the fly without editing configuration files manually. All changes are persisted in ~/.config/htop/htoprc.

6.1 Adding/Removing Columns

1. Press F2 → Columns.
2. Use ← / → to move columns between Available and Active lists.
3. Use ↑ / ↓ within the Active list to reorder.
4. Press Enter to confirm, then Esc to exit.

Common useful columns:

6.2 Changing Meters & Layout

1. F2 → Setup.

Choose a layout: Left (vertical), Right, Top, Bottom, or Compact.

1. Add/remove individual meters (CPU, Memory, Swap, Load, Uptime, Network, etc.).
2. Drag them up/down to change order.

Example:

• Move Swap to the top‑right, hide Uptime, and enable Network (if you have ifstat support).

6.3 Color Schemes & Themes

htop ships with several built‑in color palettes (e.g., default, monochrome, solarized).

• F2 → Appearance → Color Scheme – pick one.
• You can also edit ~/.config/htop/htoprc manually to set custom RGB values (advanced).

6.4 Tree View & User‑Defined Filters

• Tree view (F5 or t) shows parent‑child relationships, making it easy to see which processes belong to a given service.
• Filters (F4) hide everything that does not match a regular expression. Example: F4 → type ssh → only ssh‑related processes stay visible.
• Tagging (Space) multiple processes lets you send a signal to all of them at once (F9 → choose signal).

7. Advanced Interaction

7.1 Searching & Filtering

• Search (F3): incremental, case‑insensitive by default. Press Enter to jump to the next match, Esc to abort.
• Filter (F4): works like a permanent search; you can clear it with F4 again and an empty pattern.

Both accept regular expressions, so you can do sophisticated matches, e.g.:

F4 → ^(postgres|mysqld)

Shows only PostgreSQL or MySQL processes.

7.2 Killing, Renicing, and Tracing

Batch kill example:

1. Tag several processes with Space.
2. Press F9, select SIGTERM → all tagged processes receive the signal.

7.3 Monitoring Specific PIDs / Groups

• Use the “Follow” mode (Shift+F) while a process is selected to keep it centered as it moves up/down the list.
• Group by user: Press u, type a username, and htop will only show that user’s processes.

Start htop with -p to limit view:

htop -p 1234,5678

7.4 Using the “Setup” Menu (F2)

The Setup menu contains four tabs:

All changes are saved automatically when you leave the menu (Esc or F10).

8. Running htop in Batch Mode

Batch mode (-b) is non‑interactive and prints a snapshot (or a series of snapshots) to STDOUT. It is handy for scripts, monitoring tools, or logging.

# Single snapshot (default refresh interval = 1 sec)
htop -b -n -d 2 > /tmp/htop_snapshot.txt

• -b → batch mode.
• -n → no colour (easier to parse).
• -d <seconds> → delay between snapshots (if you use -C for continuous output).

Continuous logging example (10 snapshots, 5 s apart):

for i in {1..10}; do
    htop -b -n -d 5 >> /var/log/htop.log
    sleep 5
done

The output is a plain‑text table similar to top -b. You can pipe it to awk, grep, or sed for further analysis.

9. Saving & Loading Configurations

htop writes its configuration to:

$XDG_CONFIG_HOME/htop/htoprc
# or, if XDG not set:
~/.config/htop/htoprc

Exporting a configuration

cp ~/.config/htop/htoprc ~/my_htop_config.rc

Importing on another machine

mkdir -p ~/.config/htop
cp ~/my_htop_config.rc ~/.config/htop/htoprc
htop  # will start with the imported settings

If you maintain multiple profiles, you can keep several htoprc files and symlink the one you want before launching:

ln -sf ~/profiles/htop_server.rc ~/.config/htop/htoprc
htop

10. Common Issues & Troubleshooting

10. Quick Reference Cheat‑Sheet

F1  Help                F2  Setup
F3  Search              F4  Filter
F5  Tree view           F6  SortBy
F7  Decrease nice       F8  Increase nice
F9  Kill                F10 Quit
Space  Tag              s  Suspend
r  Resume               c  Toggle command line
u  Show user            t  Tree view
l  Load avg meter       m  Memory meter

11. Conclusion

htop is far more than a pretty replacement for top. Its interactive UI, tree view, tagging, filtering, customizable meters, and batch mode make it a powerful tool for both system administrators and developers. By mastering the keys listed above and exploring the Setup menu, you can adapt htop to virtually any monitoring workflow.

Happy monitoring! 🎛️