How to Fix PHP-FPM Startup Error Due to Missing libargon2.so.0 (or Other Shared Libraries)

Introduction

When running PHP-FPM on a cPanel server, especially after system updates or migrations, you may encounter PHP-FPM Startup Error Due to Missing libargon2.so.0 or similar errors like:

/opt/cpanel/ea-phpXX/root/usr/sbin/php-fpm: error while loading shared libraries: libargon2.so.0: cannot open shared object file: No such file or directory

This PHP-FPM Startup Error Due to Missing libargon2.so.0 typically occurs because PHP-FPM relies on certain system libraries to function correctly. If one of these shared libraries is not present or not properly configured, PHP-FPM fails to start. In this case, libargon2.so.0 is missing or PHP can’t find it. This guide walks you through resolving this issue for all installed PHP versions.

What is libargon2?

libargon2 is a password hashing library used by PHP (especially with password functions like password_hash() using ARGON2I or ARGON2ID).

Step-by-Step Fix

1. Install libargon2

If you’re using AlmaLinux 9, RHEL 9, or CentOS Stream, install the missing library with:

dnf install libargon2

On older systems (CentOS 7 / AlmaLinux 8), use:

yum install libargon2

For Ubuntu/Debian:

apt update

apt install libargon2-1

What If the Library Is Installed But Still Errors?

Sometimes, PHP-FPM expects libargon2.so.0 but only libargon2.so.1 is present. You can resolve this by creating a symbolic link:

Step 1: Locate the Installed Library

find /usr -name "libargon2.so*"

Example output:
/usr/lib64/libargon2.so.1             # RHEL-based
/usr/lib/x86_64-linux-gnu/libargon2.so.1   # Debian-based

Step 2: Create a Symlink

RHEL/CentOS:

ln -s /usr/lib64/libargon2.so.1 /usr/lib64/libargon2.so.0

Ubuntu/Debian:

ln -s /usr/lib/x86_64-linux-gnu/libargon2.so.1 /usr/lib/x86_64-linux-gnu/libargon2.so.0

Step 3: Refresh the Linker Cache

ldconfig

Step 4: Restart PHP-FPM (any version)

systemctl restart ea-php74-php-fpm     # For cPanel (ea-php)
systemctl restart php7.4-fpm           # For Ubuntu/Debian-style PHP

Use the following command to check which PHP versions are installed:

ls /opt/cpanel/ | grep ea-php

Conclusion

Missing shared libraries are a common cause of PHP-FPM startup errors. The solution is usually straightforward: install the missing package, create a symlink if necessary, and restart PHP-FPM. This general approach applies to other libraries as well — not just libargon2. 

Note: Always ensure you restart the correct PHP-FPM version after the fix.

If you’re facing challenges resolving the PHP-FPM Startup Error Due to Missing libargon2.so.0 or other similar shared library issues, our expert support team is here to help. At Skynats, we specialize in advanced server management services and troubleshooting, ensuring minimal downtime and secure environments. Contact us today to quickly fix PHP-FPM startup errors and restore your server functionality with confidence.