[humanpuff69]

OpenVZ is easy to spot in most cases:
- venet0 network adapters in "ifconfig" or "ip a" output
- 2.6.32 kernel on no matter which OS (i.e. uname -a)
- simfs or ploop filesystem on "df -h" output
- lack of most system processes in ps and htop output (since almost all system and kernel processes are ran by the host and simply shared with to the VMs)

There is probably more to it.

the kernel is always 2.6 because openvz host must run a modified 2.6 kernel that is shared with the guest . the kernel version is most easiest way to determine since most newer distro already use kernel 3 or 4 . Openvz also cannot use latest distro like ubuntu 18.04 if you try it it will brick the openvz vps because of incompatibility with the old 2.6 kernel . If openvz did not try to upgrade their kernel soon enough it will be lesa of an option from time to time due to much more package not having support for old 2,6 kernel