Ubuntu server first steps

Client: Generate keys

This command generate a two files with private and public keys. The public-key file will end with .pub extention, a private key file has no extention

ssh-keygen

Public key you may share with everyone, but private key must be keep in secret.

Best way for Ubuntu is add public key to github ssh keys, then it will be avaidable at github.com/<username>.keys

Server: Install Ubuntu-server

Becouse you install a server version, the common way to interact is remote control (.ssh), but you need to create base authorization method via physical terminal. The public key made for this purpose, but type public key by hands is takes too long, so we were publish our public key with entire ethernet at github.com/<username>.keys

While install, select import identity and enter GitHub user name. Ubuntu will automaticaly read public key and save it.

It's strongly recommended use only ssh-keys and disable password authentification.

Connect

For connect from client use this command to connect:

ssh -i ~/.ssh/some_server_name username@my.domain.com -p 22

where -i is identity path (private key path), where ~ - is home client user directory.

where -p is target port (default: 22)

where username - remote username (you enter while install)

where my.domain.com - ip of target machine or domain name

First connection from clinet to server must be as created user (not root).

If connection sucseeded and keys are valid, system ask you to add connection to known_hosts, type yes.

In case of server system reinstall old clients may see message, thats says that identity is changed. This problem rised becouse server keys stored on clinet machine is old. For fix this, in Windows, go to userfolder/.ssh and edit known_hosts. Delete lines associated with server. And try to connect again.

After install public key will be stored in ~/.ssh/authorized_keys

where ~ is user directory: /home/username.

For activate root, type this and enter password.

sudo su

Now you are login as root user and can go to /root/.ssh, this folder is already has authorized_keys file, but file is empty. This means that nobody can use ssh for login as root. For fix this you need to copy public key from user authorized_keys to root authorized_keys.

You may use this: (cat is print file content, >> is redirect output to new file line).

cat /home/<username>/.ssh/authorized_keys >> /root/.ssh/authorized_keys

Now you can connet via ssh as root.

Setup after install and connect

Extend disk space

This step may be already done while install, but if not do this:

vgdisplay
lvextend -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv
resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv
df -h

For laptops:

Disable machine sleep if laptop lid is closed and reboot for apply changes:

sudo sh -c 'echo "HandleLidSwitch=lock" >> /etc/systemd/logind.conf' && reboot

Change network Wi-Fi interface to 5GHz

iwconfig # Show interfaces
iwlist wlp2s0 frequency # Show frequency for example interface
sudo iwconfig wlp2s0 freq 5.5GHz # Change frequency
reboot # Aplly

Change hostname

Check information about host:

hostnamectl

Change hostname:

sudo hostname new_hostname

Create users

useradd -m -s /bin/bash username

Cut maximum journal disk size

sudo journalctl --vacuum-size=100M