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Persistent Network Config in CentOSnmcli | Network Manager command line | nmtui | network Manger graphical | nmcli connection up ens33 | Switch on ens33 interface | /etc/sysconfig/network-scripts | Config file |
Common Network Toolsdig | Verify DNS relay | nmap | Scanning ports |
iptables Syntaxiptables {-A|I} chain [-i/o iface] [-s/d ipaddr] [-p udp/tcp/icmp[--dport/sport nn...]] -j [LOG|ACCEPT|DROP|REJECT]
-A|I: Append or Insert
-i/o: INPUT or OUTPUT chain
-s/d: source IP or destination IP
-p udp/tcp/icmp: protocol to use
--dport/sport nn: destination port or source port
-j LOG|ACCEPT|DROP|REJECT: Write line to syslog or Accept or Drop silently (external traffic) or reject non-silently (internal traffic) |
Configuring Local timehwclock | Display kernel hardware clock | hwclock --systohc | Synchronise system tim to hardware time | hwclock --hctosys | Synchronise hardware clock to system | timedatectl | Utilitiy to config time |
NTPD and Chronydvim /etc/ntp.conf | Config file; Server server name iburst | systemctl restart ntpd | Restart NTP service | ntpq -p | Show current time info | systemctl status chrony | Show current status of chrony | vim /etc/chrony.conf | Chrony config file | chronyc sources | Current time server status | chrony tracking | Current chrony tracking status | iptables -A INPUT -p udp --dport 123 -j ACCEPT | Allow traffic to time server | iptables -A OUTPUT -p udp --dport 123 -j ACCEPT | // |
IP Traffic Routeroute -n | IP routing table | ip route list | List of ip route | ip route add 8.8.0.0/16 proto static metric 10 via inet 10.9.185.143 dev eth0 | Add new IP route | ip route del 8.8.0.0/16 proto static metric 10 via inet 10.9.185.143 dev eth0 | Delete IP route |
| | Firewalldfirewall-cmd --list-all | Show current firewall configuration | firewall-cmd --get-services | Show current services on Firewall | /usr/lib/firewalld/services | List of services config file | firewall-cmd --add-service samba --permanent | Add Samba service to Firewall persistently | firewall-cmd --add-port 4000-4005/tcp --permanent | Add port 4000-4005 on TCP persistently |
SSHvim /etc/ssh/sshd_config | Config file for SSH Daemon (SSH server) | vim /etc/ssh/ssh_config | Config file for SSH Client | systemctl status sshd | Current status of process | systemctl enable sshd | Start SSH at boot | ssh -X user@ip | SSH with graphical application | ssh-keygen | Generating public and private key | scp /etc/hosts 192.168.4.240:/tmp (vice versa) | Copy /etc/hosts over SSH to /tmp | | Rsync from host to remote |
Config static networkvim /etc/network-scripts/ifcfg-eht0
BOOTPROTO=none
IPADDR=192.168.0.222
PREFIX=24
GATEWAY=192.168.0.1
DNS1=8.8.8.8
systemctl restart network |
| | Hostnamevim /etc/hostname | Hostname config file | hostnamectl | Tool for setting hostname | vim /etc/hosts | Local resolving of hostname | vim /etc/resolv.conf | DNS config file | vim /etc/nsswitch.conf | Specify which config file to be processed |
Firewall using iptablessystemctl stop firewalld | Stop Firewalld | iptables -L -v | List iptables policy verbosely | iptables -P INPUT(OUTPUT) DROP | Set INPUT(OUTPUT) to DROP | iptables -A INPUT -i lo -j ACCEPT | Allow incoming traffic to loopback interface | iptables -A OUTPUT -o lo -j ACCEPT | Allow outgoing traffic to loopback interface | iptables -A INPUT -p tcp --dport 22 -j ACCEPT | Allow packet through port on TCP going to system | iptables -A OUTPUT -m state --state ESTABLISHED, RELATED -j ACCEPT | Allow all old to get out of system; doesn't all new traffic | iptables -A OUTPUT -p tcp --dport 22 -j ACCEPT | // | iptables -A INPUT -m state --state ESTABLISHED, RELATED -j ACCEPT | // | iptables -A OUTPUT -p tcp --dport 80 -j ACCEPT | Allow TCP traffic going out through port 80 | iptables -A OUTPUT -p udp --dport 53 -j ACCEPT | Allow traffic going out through DNS (port 53) | iptables-save > /etc/sysconfig/iptables | Save iptables to start automatically at boot |
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