Tag Archives: redhat

Tips for RHCSA certification

Just a collection of notes and screenshot that can help in getting ready for the RHCSA exam.
Basted on RHEL 7.

 

Boot systems into different targets manually

 

 Configure networking and hostname resolution statically or dynamically

 

Interrupt the boot process in order to gain access to a system

 

Mount and unmount CIFS network file systems

 

Configure a system to use time services

timedatectl

timedatectl list timezones
timedatectl set-timezone America/Phoenix


timedatectl set-time 9:00:00
timedatectl set-ntp true/false
timedatectl

 

Bridge / Bond interfaces CentOS/RedHat

Just few notes about how to bridge or bond network interfaces in CentOS/RedHat systems

# Install the required packages

yum install bridge-utils


BRIDGE
------

/etc/sysconfig/network-scripts/

#ifcfg-br0
DEVICE=br0
TYPE=Bridge
IPADDR=192.168.1.1
NETMASK=255.255.255.0
ONBOOT=yes
BOOTPROTO=none
NM_CONTROLLED=no
DELAY=0

#ifcfg-eth0
DEVICE=eth0
TYPE=Ethernet
HWADDR=AA:BB:CC:DD:EE:FF
BOOTPROTO=none
ONBOOT=yes
NM_CONTROLLED=no
BRIDGE=br0


#### USE SCREEN!!
service network restart 

================================
BOND >>> 2 or more eth interfaces!
----

#ifcfg-eth0
DEVICE=eth0
TYPE=Ethernet
USERCTL=no
SLAVE=yes
MASTER=bond0
BOOTPROTO=none
HWADDR=AA:BB:CC:DD:EE:FF
NM_CONTROLLED=no

#ifcfg-eth1
DEVICE=eth1
TYPE=Ethernet
USERCTL=no
SLAVE=yes
MASTER=bond0
BOOTPROTO=none
HWADDR=AA:BB:CC:DD:EE:FF
NM_CONTROLLED=no

#ifcfg-bond0
DEVICE=bond0
ONBOOT=yes
BONDING_OPTS='mode=1 miimon=100'
BRIDGE=br0
NM_CONTROLLED=no

#ifcfg-br0
DEVICE=br0
ONBOOT=yes
TYPE=Bridge
IPADDR=192.168.1.1
NETMASK=255.255.255.0
NM_CONTROLLED=no


# ifup bond0
#### USE SCREEN!!
# service network restart 


==========================

For DHCP and not static

DEVICE=eth0
BOOTPROTO=dhcp
ONBOOT=yes

 

Sources:

RPM – Yum notes 

>> update all, including what is set as exclude in yum.conf
# yum check-update --disableexcludes=all

>> update only the security related patches the server
# yum update --security

>> how to rollback a recent package
# rpm -Uvh --rollback '1 hour ago'

>> check if a packaged is patched against a particular CVE with:
rpm -q --changelog {package-name} | grep CVE-NUMBER 

>> Check if a package is from repository or not
Example: httpd

1) Get the PID of httpd
# netstat -tnlp | grep httpd
tcp        0      0 :::80                       :::*                        LISTEN      7568/httpd          
tcp        0      0 :::443                      :::*                        LISTEN      7568/httpd        

# lsof -p 7568 | less
(and find what's the "bin" for httpd, in this case is /usr/sbin/httpd )

# rpm -qf /usr/sbin/httpd
httpd-2.2.15-30.el6_5.x86_64

Verified: package part of RH repositories