Technology

Wednesday, 5 February 2020

CentOS 8

ip a / ip address #show ip address
nmtui #NetworkManager TUI
nmcli d #NetworkManager device

yum install epel-release
yum update
yum install dnf
yum install vim
dnf install chrony

yum install iftop htop telnet tmux #iftop -i eth0 #telnet only for test tcp port

yum install nc #nc -z -v -u 192.168.10.12 161 #nc for test udp port

yum install traceroute
yum install nmap #nmap -sU 192.168.10.12 to scan udp port
yum install iperf3
yum install bind-utils #dig

yum install httpd
yum install mariadb-server
dnf install php php-opcache php-gd php-curl php-mysqlnd

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Network interface configuration file:

[root@PacketFence-ZEN ~]# vim /etc/sysconfig/network-scripts/ifcfg-ens160

TYPE=Ethernet

PROXY_METHOD=none

BROWSER_ONLY=no

BOOTPROTO=static #or none/dhcp

DEFROUTE=yes #yes: This interface is set as the default route for IPv4|IPv6 traffic.

IPV4_FAILURE_FATAL=no #no: This interface is not disabled if configuration fails.

IPV6INIT=yes #yes: Enable IPv6 on this interface.

IPV6_AUTOCONF=yes

IPV6_DEFROUTE=yes

IPV6_FAILURE_FATAL=no

IPV6_ADDR_GEN_MODE=stable-privacy

NAME=ens160

UUID=27f5f975-99f0-444d-a2f0-2e0a039810d3

DEVICE=ens160

ONBOOT=yes yes: This interface is activated at boot time.

HWADDR=08:00:29:5b:85:77

IPADDR=10.10.10.79

PREFIX=24

GATEWAY=10.10.10.1

DNS1=8.8.8.8

DNS2=8.8.4.4

[root@PacketFence-ZEN ~]# vim /etc/hosts

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4

::1 localhost localhost.localdomain localhost6 localhost6.localdomain6

1.2.3.4 www.google.com

[root@PacketFence-ZEN ~]# vim /etc/resolv.conf

nameserver 8.8.8.8

nameserver 8.8.4.4

[root@PacketFence-ZEN ~]# vim /etc/sysconfig/network #This file specifies global network settings

GATEWAY=10.10.10.1

Restart Network Services:
systemctl restart NetworkManager
nmcli networking off; nmcli networking on

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NTP:
dnf install chrony

systemctl enable chronyd

vim /etc/chrony.conf

allow 192.168.0.0/16 #If want to set Chrony to act as an NTP server for a local network.

Server 192.168.1.150 #if want to set Chrony to act as an NTP client.

systemctl restart chronyd

firewall-cmd --permanent --add-service=ntp

firewall-cmd --reload

chronyc sources     #Check for NTP server sources.

timedatectl   #Read clock, RTC(hardware clock)
timedatectl set-local-rtc 1   #change the hardware clock time standard to localtime
timedatectl set-local-rtc 0   #revert to the hardware clock being in UTC
timedatectl set-timezone Asia/Kuala_Lumpur
timedatectl set-ntp yes
timedatectl set-ntp on
yum install ntp
ntpq -p
hwclock
ntpdate pool.ntp.org
ntpdate -u pool.ntp.org
logfile /var/log/ntp.log   #If you logfile
ss -atun | grep 123   #check if ntpd daemon is listening on it’s port

#####################################################

TMUX:

[root@centos8 ~]# tmux #Creating sequence name Tmux Sessions

[root@centos8 ~]# tmux new -s session_name #Creating Named Tmux Sessions

Ctrl+b d #Detaching from Tmux Session

[root@centos8 ~]# tmux ls #list all Tmux Session

[root@centos8 ~]# tmux attach-session -t 0 #Re-attaching to Tmux Session

Ctrl+b % #Split current pane horizontally into two panes

Ctrl+b " #Split current pane vertically into two panes

Ctrl+b o #toggle between panes

#####################################################

yum install net-snmp net-snmp-utils

systemctl enable snmpd

vim /etc/snmp/snmpd.conf

com2sec notConfigUser default <CommunityName>

group notConfigGroup v2c notConfigUser

view allview included .1

access notConfigGroup "" any noauth exact allview none none

systemctl restart snmpd

RHEL 8 / CentOS 8 recover root password

https://linuxconfig.org/redhat-8-recover-root-password

1. Boot to the GRUB menu and enter the edit mode. Use your arrows to navigate to the the menu item you would normally boot your RHEL 8 Linux system from. Press e to start editing the selected menu item.

2. Perform a break at an early stage of the boot process by typing rd.break at the end of the line starting with kernel=. Once ready press CTRL+X to start the RHEL 8 boot process.

3. Check write access on the /sysroot mount point. By default this mount point is mounted only with the read-only (ro) access. Execute:

switch_root:/# mount | grep sysroot

4. Remount the sysroot directory with read & write access. To do so execute:

switch_root:/# mount -o remount,rw /sysroot/
switch_root:/# mount | grep sysroot

5. Enter chroot system by executing:

switch_root:/# chroot /sysroot

6. Use the passwd command to set a new root password. Please note that when typing a new password the characters you type will not be visible. Simply keep typing.