Ubuntu 20 or later with GNOME automatically mounts external USB drives for logged-in console users. However, this feature doesn't work on headless servers. To auto-mount USB drives on a headless server, use this tool: 

https://github.com/raamsri/automount-usb

Install

sudo apt install vlock

Usage

vlock --current        # lock current terminal

vlock --all            # lock all termianls

$ sudo apt install power-profiles-daemon

$ powerprofilesctl set power-saver

$ powerprofilesctl

$ more /proc/cpuinfo | grep "cpu MHz"

Reference

• Enable hibernate, https://ubuntuhandbook.org/index.php/2021/08/enable-hibernate-ubuntu-21-10/
• CPU power mode, https://ubuntuhandbook.org/index.php/2023/10/command-cpu-power-mode-ubuntu-22-04/

Install upower

sudo apt-get install upower

Commands:

$ upower -e
$ upower -d
$ upower -i <object>

Configuration

/etc/UPower/UPower.conf

Service

$ sudo systemctl restart upower.service
$ sudo systemctl status upower.service

Alias

alias battery='upower -d | grep -m 2 -e '\''percentage'\'' -e '\''time to empty'\'' | sed '\''s/^[ \t]*//'\'''

1. Change Port number in sshd_config

Port <new port>

$ sudo systemctl restart ssh

2. Change IPTables entry

$ sudo vi /etc/iptables/rules.v4

-A INPUT -p tcp -m state --state NEW -m tcp --dport <new port> -j ACCEPT

$ sudo iptables-restore < /etc/iptables/rules.v4

3. Change in Security List

Go to Security List for that VCN and Subnet.  Add <new port> with TCP protocol.