What is conntrack and how can I check how many sessions I am using?

Conntrack is a table that stores information about all connections to/from a VPS. Here is a good explanation on how it works: http://www.rigacci.org/wiki/lib/exe/fetch.php/doc/appunti/linux/sa/iptables/conntrack.html

A normal Linux OS has a maximum of 65536 conntrack sessions by default, these sessions all require memory which is used by the host node and not by the VPS so setting this limit to high can impact the whole node and allow users to use more RAM than their VPS has allocated by eating up the host's RAM. Any VPS that uses over 20000 conntrack sessions will automatically be suspended by our automated system.

A typical VPS should never use more than 10000 sessions at any given time although we do have some busy NTP servers that peak at 20000 once in a while. To check your conntrack sessions, run the following command in your VPS: cat /proc/net/nf_conntrack
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