Previously, k3s.service was failing when the EnvironmentFile does not exist:
```
Feb 02 17:17:30 suda-ws01 systemd[1]: k3s.service: Failed to load environment files: No such file or directory
Feb 02 17:17:30 suda-ws01 systemd[1]: k3s.service: Failed to run 'start' task: No such file or directory
Feb 02 17:17:30 suda-ws01 systemd[1]: k3s.service: Failed with result 'resources'.
Feb 02 17:17:30 suda-ws01 systemd[1]: Failed to start Lightweight Kubernetes.
```
ref: https://unix.stackexchange.com/questions/404199/documentation-of-equals-minus-in-systemd-unit-files
Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
Wants= is required to actually set the dependency on network-online.service
After= is required or k3s.service will be started at the same time as network-online.service
In network environments with slow DHCP, both are required to ensure valid network configuration for k3s
Signed-off-by: Adam Farden <adam@farden.cz>
When k3s is installed on an OS with default high ulimits, performance
issues can be observed. This was discovered on CoreOS where the default
value is 1073741816. Symptoms include very slow file operations such
as installing a Rook/Ceph cluster will take ~6 hours instead of ~10 minutes.
A google search for 'container LimitNOFILE' will show that most major
projects set this already, including the (unused) containerd systemd unit
found in this repository at /vendor/github.com/containerd/containerd/containerd.service
k3OS is not affected becuasse the default there is already 1048576.
See description in coreos/fedora-coreos-tracker#329
Cert generation may cause slow startup times for some systems such as
the Raspberry Pi, set the systemd service TimeoutStartSec to Infinity to
avoid startup timeouts.
Akihiro Suda