On Linux, checking which processes are using system resources starts with viewing the process list. htop is an interactive, text-based process viewer that refreshes system and process information in a terminal.
I’ll show you how to install htop and use its process list to inspect CPU and memory use.
TL;DR
Install htop with your distribution’s package manager, run htop, and use its process list to inspect CPU and memory use.
- Debian or Ubuntu: sudo apt install htop.
- Fedora: sudo dnf install htop.
- Press F3 to search, F4 to filter, and F10 or q to quit.
What Is htop in Linux?
htop is an interactive, text-based process viewer that refreshes system and process information in a terminal.
The top area groups resource meters with task counts, load average, and uptime. Each process row includes a PID, owner, CPU use, and resident memory.
Load average describes runnable and uninterruptible work over time. Compare it with the number of available CPUs rather than treating it as a percentage.
Unlike the top command, htop keeps updating and lets you act on selected rows. The upstream project and its manual page document its controls.
How to Use htop in Linux Step by Step
Start with the distribution package, then use the changing process list to find and inspect a task.
Step 1: Install htop from your distribution
htop opens its live process view with configured defaults, and startup options change its initial display before interactive keys take over.
htop syntax starts with the program name, followed by optional flags and their values. Flags affect the initial display, while the interactive keys change what you inspect after launch.
Package managers vary by distribution. The upstream download page lists apt for Debian-based systems, dnf for Fedora, and pacman for Arch.
# Debian or Ubuntu
sudo apt install htop
# Fedora
sudo dnf install htop
# Arch Linux
sudo pacman -S htop
I checked the available package metadata with apt-cache policy htop. The installed and candidate versions matched:
htop:
Installed: 3.3.0-4build1
Candidate: 3.3.0-4build1
These installation commands require administrator permission and change the system, so consult your distribution documentation before running one. I did not run an installation command. The LinuxForDevices htop installation guide covers other package routes.
Step 2: Open the live process view
Run htop in a terminal that supports a full-screen text interface:
htop
I ran htop --version and got this output:
htop 3.3.0
This confirms the executable starts. The interactive view is where you inspect live processes.
RES is resident memory, while VIRT includes address space that may not reside in RAM. Use RES when comparing memory currently held in physical memory.
Step 3: Find and narrow the process list
Select a row with the arrow keys. Press F3 to search command text or F4 to filter the visible rows. Search moves between matches.
Filtering hides non-matching rows until you clear it.
When scanning the list, compare CPU% for active processor use and RES for resident memory. Sorting changes row order, while filtering changes which rows remain visible.
Press F6 to choose a sort column such as CPU% or RES. Startup flags can narrow the initial view before you begin navigating.
Use startup options to narrow the view
The -d option sets the update delay in tenths of a second. A larger delay refreshes the display less often, which can help you follow a busy view.
The -u option limits the displayed processes to a named user, while -p accepts one or more process IDs. Use these when you know the account or identifiers before launch. Every flag shown here appears in the command block:
htop -d 20
htop -u username
htop -p 1234,5678
Replace the sample username and IDs with values from your system. Here, -d 20 requests a two-second update interval.
For another view of process ownership and resource use, see the LinuxForDevices guide to finding processes with high CPU or memory use. A process list does not combine separate processes that happen to share a command name.
Step 4: Inspect before sending a signal
Before using F9, check that the selected row and owner identify the intended task.
A termination signal can interrupt unsaved work, so leave a process running when its identity is unclear.
Press F10 or q to leave htop.
If a function key is intercepted, use the alternative shown in the bottom legend or consult the manual.
Common htop Limits and Fixes
Installation, terminal size, and option mismatches can prevent a useful view. Check the symptom before changing a setting or sending a signal.
| Case | Symptom | Fix |
|---|---|---|
| Package absent | Shell reports command not found | Install htop from the distribution repository |
| Unsupported option | htop rejects the argument | Remove it and check the installed manual |
| Terminal too small | Columns or meters are hard to read | Expand the terminal window |
| Search misses a PID | F3 does not isolate the numeric ID | Use a known PID with the documented startup option |
| Limited process details | Some host processes or fields are absent | Check permissions, container limits, and F2 column settings |
I passed an unsupported flag and got “htop: unrecognized option ‘--bad-option’”. Remove that flag, then consult htop --help or man htop for the installed version.
For a command-line process snapshot, the LinuxForDevices ps guide covers a complementary tool.
Use htop --help or man htop when an option is rejected. The manual matches the version installed by your distribution, so it is the reference for accepted flags and key bindings.
Conclusion
For platform support details, consult the official htop project.
FAQ
These answers cover common installation and navigation questions.
How do I install htop on Linux?
Use your distribution’s package manager. Debian and Ubuntu use apt, Fedora uses dnf, and Arch Linux uses pacman.
How do I exit htop?
Press F10 or q to quit the interactive process view.
How do I filter processes in htop?
Press F4 and enter text to filter matching process rows. F3 searches and moves between matches.