Linux Stuff

Documentation of linux command I have used

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Used to Identify Network interfaces

        nmcli d

Create Netplan for static ehternet

        sudo nano /etc/netplan/01-netcfg.yaml

Example YAML for ehternet

network:
  version: 2
  renderer: networkd
  ethernets:
    eno1:
      dhcp4: no
      addresses:
        - 192.168.1.120/24
      routes:
        - to: default
          via: 192.168.1.1
      nameservers:
        addresses: [8.8.8.8, 8.8.4.4]

Secure Config file

        sudo chmod 600 /etc/netplan/01-netcfg.yaml

Apply Net Plan

        sudo netplan apply

Verify IP

        ip a

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Show connections

        nmcli connection show

Show active connections

        nmcli connection show --active

Show details about connections

        nmcli connection show "Wired connection 1"

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Disable and Enable WIFI

        nmcli radio wifi off
        nmcli radio wifi on

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Setup DHCP server

    sudo apt install isc-dhcp-server

Expands to sudo mv /etc/dhcp/dhcpd.conf /etc/dhcp/dhcpd.conf.backup

    sudo mv /etc/dhcp/dhcpd.conf{,.backup}

Configure DHCP

    	sudo nano /etc/dhcp/dhcpd.conf
                # a simple /etc/dhcp/dhcpd.conf
                    default-lease-time 600;
                    max-lease-time 7200;
                    authoritative;
                    
                    subnet 192.168.1.0 netmask 255.255.255.0 {
                    range 192.168.1.100 192.168.1.200;
                    option routers 192.168.1.254;
                    option domain-name-servers 192.168.1.1, 192.168.1.2;
                    #option domain-name "mydomain.example";
                    }

Bind DHCP to particular interfaces

File to Edit

    sudo nano /etc/default/isc-dhcp-server

Example

        INTERFACESv4="eth0"

Restart DHCP

sudo systemctl restart isc-dhcp-server.service

enable dhcp service through firewall

    sudo ufw allow 68/udp 
    sudo ufw reload

check DHCP Status

sudo systemctl status isc-dhcp-server.service

Check if config is valid

    sudo dhcpd -t -cf /etc/dhcp/dhcpd.conf

check status of dnsmasq
```
sudo systemctl status dnsmasq.service
```
See what service might be using a port or protocol
```
sudo netstat -tuln | grep :53
```
Search for file
```
sudo find -name "query"
```

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SSH Status

    sudo systemctl status ssh

Allow SSH thru firewall

    sudo ufw allow ssh
    sudo ufw enable

Another Check Service Status

    service ssh status

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Show IP Route Tables

ip route show table 100
ip route show table 200
ip rule show

Bring up Network Card

ip ip link set {interfacename} up

Show DNS Info

resolvectl status

Release Renew IP

sudo systemctl restart systemd-networkd