Nothing is more frustrating than having sudo configured to allow all commands, yet still receiving ‘Permission denied’ errors.
This paradoxical situation has vexed Linux administrators for years.
Even when a sudoers file explicitly grants a user unrestricted access (user1 ALL=(ALL) NOPASSWD: ALL), running basic commands fails with cryptic error messages.
The root cause often lies not in the sudoers configuration itself, but in underlying system permission issues.
The most common culprits include file permission problems on the target executable, incorrect ownership of critical system directories, or filesystem mount issues that restrict access to certain areas of the system.
Additionally, recent sudoers security updates have introduced new constraints.
CVE-2025-32462 identified a critical privilege escalation vulnerability in sudo versions before 1.9.17p1 when used with specific host configurations.
Organizations have been forced to update their sudo implementations, sometimes introducing new compatibility issues in the process.
Diagnostic Steps:
- Check file permissions on the target executable using: ls -la /path/to/command
- Verify the sudoers file syntax with: sudo visudo (this prevents syntax errors)
- Check if the filesystem is mounted read-only: mount | grep ‘ro,’
- Ensure your sudo version is up to date: sudo –version
Bibliography:
- Red Hat Customer Portal. (2024, June 13). Permission denied when running any SUDO commands. Retrieved from https://access.redhat.com/solutions/6217761
- Adams, B. (2025, September 5). Why does sudo echo fail with permission denied? Retrieved from https://www.adamsdesk.com/posts/sudo-echo-permission-denied/
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