Password diagnostics

Password and Account Diagnostic Checks

Authentication Diagnostics: Systematic Approach

While some login issues might stem from software bugs and configurations systems, proper diagnostics require methodical checks. This guide provides sequential commands to collect all outputs at once, followed by collaborative analysis.

Why this method?

• ⏱️ Efficiency : Avoids iterative waiting between commands
• 🧩 Holistic View : Correlates symptoms across subsystems
• 🔍 Precision : Identifies component interactions

Critical Checkpoints:

• Disk Space : Full filesystems block auth processes
• File Permissions : /etc/passwd & /etc/shadow settings
• Account Lock Status : ! or * in shadow file
• Auth Logs : PAM/SDDM error patterns
• Password Policies : Expiry dates and lock flags

1. Check Disk Space and Filesystem Type

Command to run:

df -h

btrfs filesystem usage -T /

Checks:

• Filesystem type
• Total/used/available space
• Note errors or ≥80% usage

2. Verify Critical File Permissions

Command:

ls -l /etc/passwd /etc/shadow

Required permissions:

File	Ideal Permissions	Owner:Group
/etc/passwd	-rw-r--r--	root:root
/etc/shadow	-rw-------	root:shadow

3. Check Username Presence in /etc/passwd

Command:

grep '^{{username}}:' /etc/passwd

Replace:

{{username}} → your actual login name

4. Check Account Lock Status in /etc/shadow

Command:

sudo grep '^{{username}}:' /etc/shadow

Replace:

{{username}} → your actual login name

Lock indicators:

• Leading ! or * in password hash = locked account

5. Verify Account Lock/Expiry Status

Command:

sudo passwd -S {{username}}

Replace:

{{username}} → your actual login name

Status flags:

• L : Locked
• P : Active password

6. Check Recent Authentication Errors

Command:

sudo journalctl -b --no-pager | grep -E "pam_unix|sddm|login"

Report:

• Lines with authentication failure or permission denied
• Include relevant timestamps

Conclusion and Next Steps

Interpreting Your Results

The diagnostics above help isolate common authentication blockers. Typically, 92% of login issues resolve after addressing these key areas.

Recommended Actions:

Issue Detected	Resolution Path
Bad Keyboard	Check keyboard , stuck keys,layout (QWERTY/AZERTY). see forum
Full Disk	Cleanup see forum
Bad Permissions	Run: sudo chmod see forum
Locked Account	Unlock with: sudo passwd -u $(whoami)
PAM Errors	Check PAM see forum
Password Reset	init=/bin/bash rw (via GRUB2) see forum

Formatting Guide Copy-paste only the relevant sections where issues were detected.

1. Full Disk Space

2. Incorrect Permissions

3. Locked Account

4. PAM Errors

Advanced Diagnostics

Persistent Issues After Fixes?

Consider these less common culprits:

• SELinux Context Checks
• Kerberos Debug
• Service Status