How To Fix ‘ ps: command not found ‘ Error in Linux

The Critical ps Command

The ps command is used on Linux and UNIX systems to get a snapshot of currently running processes. It’s critical for viewing and analyzing system and application tasks.

Running just ps shows all processes for the current user. Common flags include:

• ps aux – Show all processes for all users
• ps axjf – Show process tree with PIDs
• ps -ef – Show full format listing

With such important functionality, the “command not found” error can impede Linux admins and developers. Let’s examine the root cause.

Understanding the procps and procps-ng Packages

The ps program is part of the procps or procps-ng packages containing system and process utilities:

• procps – Original sysadmin package containing ps, top, free, etc. Still used on some distros.
• procps-ng – Modern fork with additional features. Used on most modern Linux distributions.

If these packages are not installed or corrupted, trying to use ps will result in command not found errors. Let’s go through some troubleshooting steps.

Verify Procps is Installed

On Debian, Ubuntu, Linux Mint, and other deb-based distros, check that procps or procps-ng is present:

dpkg -l procps

If not installed, you’ll see:

dpkg-query: no packages found matching procps

On Fedora, CentOS, RHEL, and other RPM-based systems, check rpm:

rpm -q procps

If missing, it will error:

package procps is not installed

So first step is to verify procps/procps-ng is actually present. If not, we need to install it.

Reinstall Procps Package

If the procps or procps-ng package is not installed, simply reinstall it using your distro’s package manager:

Debian/Ubuntu/Mint

sudo apt update
sudo apt install procps

Fedora/CentOS/RHEL

sudo yum update
sudo yum install procps-ng

Arch/Manjaro

sudo pacman -Syu procps-ng

This will fetch and install the required procps package containing ps and related utilities.

Check Dependencies are Installed

Besides procps itself, often a missing library or dependency can cause “command not found” issues.

Check that essential libraries like libc and libproc are present:

Debian/Ubuntu/Mint

sudo apt install libc6 libprocps6

Fedora/CentOS/RHEL

sudo yum install glibc libproc

Arch/Manjaro

sudo pacman -Syu glibc libprocps

Install any missing dependencies for your distro to restore ps.

Look For Corrupted Packages

If procps and dependencies are installed but ps still fails, a corrupted package could be the culprit.

Try reinstalling procps and related packages to replace any corrupted files:

# Debian/Ubuntu 
sudo apt install --reinstall procps libc6 libprocps6

# Fedora/CentOS
sudo yum reinstall procps-ng glibc libproc

# Arch/Manjaro
sudo pacman -S --overwrite procps-ng glibc libprocps

This will fetch a fresh set of files which often resolves issues.

Alternative Fixes If Procps Can’t Be Restored

If for some reason procps and ps cannot be repaired, there are alternatives:

Use pgrep instead

The pgrep command offers some of ps functionality like filtering and listing processes by name:

pgrep python

Lists python processes. Add -a to show full commands:

pgrep -a python

Parse /proc Directly

The Linux /proc virtual filesystem contains live process information that can be parsed:

# Get process names
ls -l /proc | awk '{print $9}' 

# Get detailed process info
cat /proc/<PID>/status

This can provide process data without relying on ps.

Install htop

The htop interactive viewer provides advanced process monitoring and management capabilities as an alternative to ps and top. Install htop using your distro’s package manager.

Summary of Resolutions

To summarize, if encountering a “ps: command not found” error, try:

1. Check procps/procps-ng is actually installed
2. Reinstall or install procps package if missing
3. Install any required dependencies like libc
4. Check for and reinstall corrupted packages
5. Use pgrep for some basic process listings
6. Parse /proc directly or install htop as alternative

Following this troubleshooting flow will help restore ps functionality or provide workable alternatives.

Key Takeaways for Fixing the ps Error

To recap, the key takeaways for resolving the ps “command not found” issue on Linux:

• The ps command lives in the procps or procps-ng package
• Reinstall procps/dependencies if missing or corrupted
• pgrep offers partial ps query functionality
• Parse /proc directly for process data
• Install htop for full-featured interactive process viewer

Keeping these troubleshooting steps in mind will allow you to quickly resolve procps errors and regain process visibility on any Linux system.

Conclusion

While “ps: command not found” errors may seem cryptic initially, this guide equips you to thoroughly diagnose and fix missing procps packages or dependencies in order to restore the essential ps functionality.

Leveraging the package manager, examining dependencies, and trying alternatives allows you to query running processes even if ps remains unavailable. With these tools and techniques, you can troubleshoot and resolve ps errors confidently. Never let a missing process utility slow you down again!