Setting up reverse DNS on an IP address allows mailbox providers to verify the sender when they do a reverse DNS lookup upon receipt of the emails you send. When you update your DNS provider with a DNS record provided by SMTP relay providers, and then send mail over your IP, the recipient’s email service provider performs a reverse DNS lookup (rDNS) using an A Record (address record). An A Record maps your domain to your IP address. When a mailbox provider looks up your A Record, they see your SMTP relay provider’s IP address. When they look at your IP address, they see the rDNS that match your A Record. This circular checking proves your SMTP relay IP association with your domain and your domain association with your SMTP relay IP.

https://sendgrid.com/docs/ui/account-and-settings/how-to-set-up-reverse-dns/

Change the authentication method in the PostgreSQL configuration file pg_hba.conf from md5 to trust and reload the configuration.

#Approach A (Bitnami installations using system packages):
sudo sed -ibak 's/^\([^#]*\)md5/\1trust/g' /opt/bitnami/postgresql/conf/pg_hba.conf
sudo -u postgres pg_ctl reload

#Approach B (Self-contained Bitnami installations):
sudo sed -ibak 's/^\([^#]*\)md5/\1trust/g' /opt/bitnami/postgresql/data/pg_hba.conf
sudo -u postgres pg_ctl reload

Connect to the PostgreSQL database and set the password to a new value:

psql -U postgres
postgres=# alter user postgres with password 'NEW_PASSWORD';
postgresl=# \q

Finally, change the authentication method back to md5 and reload the old PostgreSQL configuration:

#Approach A (Bitnami installations using system packages):
sudo sed -ibak 's/^\([^#]*\)trust/\1md5/g' /opt/bitnami/postgresql/conf/pg_hba.conf
sudo -u postgres pg_ctl reload

#Approach B (Self-contained Bitnami installations):
sudo sed -ibak 's/^\([^#]*\)trust/\1md5/g' /opt/bitnami/postgresql/data/pg_hba.conf
sudo -u postgres pg_ctl reload

From the terminal one can connect by using the following command:

ssh user@remote-server

From Files manager, go to Other Locations and then enter the remote address at the bottom of the window

Install the following packages

sudo apt install openvpn network-manager-openvpn network-manager-openvpn-gnome
or
sudo apt install network-manager-l2tp network-manager-l2tp-gnome

Then, restart network-manager

sudo service network-manager restart

For OpenVPN, import the following configuration

sudo nmcli connection import type openvpn file huawei.ovpn

For l2tp, configure IPSec pre-shared key, phase 1 and phase 2 algorithms

Phase1 Algorithms: enc-integ-group 
                   aes128-sha1-modp1024
Phase2 Algorithms: enc-integ
                   aes128-sha1

If it doesn’t work, reboot the computer and try again with the previous command.

The basic command used to view cluster objects is

kubectl get pods,svc,ingress.. -n <namespace>

However, this command doesn’t always work. Particularly, in situations when the namespace is being terminated. If this is the case, a more advanced command can be used:

kubectl api-resources --verbs=list --namespaced -o name | xargs -n 1 kubectl get --show-kind --ignore-not-found -l <label>=<value> -n <namespace>

Create rancher-cluster.yml file, containing all the nodes, following the official example : https://rancher.com/docs/rancher/v2.x/en/installation/ha/kubernetes-rke/

rke up --config ./rancher-cluster.yml

Install helm and run all prerequisites for installing it: https://rancher.com/docs/rancher/v2.x/en/installation/ha/helm-rancher/

kubectl -n kube-system create serviceaccount tiller

kubectl create clusterrolebinding tiller \
  --clusterrole=cluster-admin \
  --serviceaccount=kube-system:tiller

helm init --service-account tiller

Install rancher

helm install rancher-latest/rancher \
  --name rancher \
  --namespace cattle-system \
  --set hostname=<rancher.url>

Backup & rollback cluster: https://rancher.com/docs/rke/latest/en/etcd-snapshots/

rke etcd snapshot-save --config cluster.yml --name snapshot-name 
rke etcd snapshot-restore --config cluster.yml --name snapshot-name

Additional step, fix rancher ingress route with tls.source=letsEncrypt by running:

kubectl edit ingress/<rancher.ingress> -n cattle-system