Fixing "No Space Left on Device (28)" & Session Write Errors in PHP

For other PHP-session errors, see Fixing session_start() failed: Permission denied (13).

Check Disk Space

Run the following command:

df -h

If /var or /tmp is 100% full, free up space by deleting unnecessary files:

sudo rm -rf /var/log/*.gz
sudo rm -rf /var/tmp/*
sudo rm -rf /tmp/*

After freeing space, restart Apache or Nginx:

sudo systemctl restart apache2

or

sudo systemctl restart nginx

Check Inodes (If Disk Space is Available)

Even if disk space is not full, inodes might be exhausted.

Check inode usage:

df -i

If inodes are full (e.g., 100% usage), clear unused session files:

sudo rm -rf /var/lib/php/sessions/*

Restart PHP & Web Server

sudo systemctl restart php8.0-fpm
sudo systemctl restart apache2

Verify session.save_path in php.ini

If the error persists, check the session storage path.

Locate php.ini

Find your active PHP configuration:

php --ini | grep "Loaded Configuration File"

Edit the file:

sudo nano /etc/php/8.0/apache2/php.ini

or for PHP-FPM:

sudo nano /etc/php/8.0/fpm/php.ini

Update Session Settings

Find:

session.save_path = "/var/lib/php/sessions"

If /var/lib/php/sessions is full or restricted, use /tmp/php_sessions instead:

session.save_path = "/tmp/php_sessions"

Save & Restart Services

sudo systemctl restart php8.0-fpm
sudo systemctl restart apache2

Check Permissions on the Session Directory

Ensure PHP can write to the session folder:

sudo chmod -R 770 /var/lib/php/sessions
sudo chown -R www-data:www-data /var/lib/php/sessions  # For Apache
sudo chown -R nginx:nginx /var/lib/php/sessions        # For Nginx

Summary of Fixes

Issue	Fix
Disk space full	Run df -h and delete unnecessary files
Inodes full	Run df -i and delete session files
Wrong session.save_path	Change it to /tmp/php_sessions in php.ini
Permissions issue	Set chmod -R 770 /var/lib/php/sessions

Now PHP sessions should work properly!