This one solves my problem on my php7
A quick command to delete all sess* files on /var/lib/php/sessions is this:
find /var/lib/php/sessions -type f -cmin +24 -name “sess*” -exec rm -f {} \;
Reference:
http://www.queryadmin.com/1634/bash-script-delete-php-session-files-free-inodes/

For php5 you can try this one:
https://pim.famnit.upr.si/wordpress/index.php/2011/04/20/running-out-of-inodes-no-space-left-on-device-php-not-cleaning-sessions/

On Ubuntu there should be a cron job configured to delete unused session files on a regular basis located in /etc/cron/php5.

Running out of inodes just means that you have too many files. If you are no longer using hhvm you can simply delete those files (or uninstall unneeded software) to free them up.

Hello, all

You can clear the session files using the find command. You can navigate to the session save path and execute the command:

find . -type f -name 'sess_*' -delete

This will delete all files which name start with sess_ you can adjust this if the session files have a different name.

Please be extra careful when executing commands that delete your data and make sure that you’re in the proper directory.

Regards,
Alex