Check remaining disk space

df -h
Reports free space on each mount.

Monitor web server in real time

tail -f /var/www/yoursite/logs/access.log
Reads Apache access long file and displays changes in real time. Your log file may be in different location depending on settings.

Permissions

chmod -R 777 tmp
Set permissions to 777 in folder tmp recursively

find . -type f -exec chmod 644 {} \;
Find all files and current directory and change permissions to 644

find . -type d -exec chmod 755 {} \;
Find all folders in current directory and change permissions to 755