Boot your Linux server from rescue disk.
At boot: prompt, press F5 then type command linux rescue.
Find superblock locations for /dev/sda3:
# dumpe2fs /dev/sda3 | grep superblock
FSCK from Linux Rescue Mode
1. Boot server/VM in BIOS mode and change Boot Mode to CD
2. Boot server/VM from Linux CD
3. Hit F5 to enter Rescue Mode.
How to Reset root Password Linux Server in Rescue Mode
1. Boot server/VM in BIOS mode and change Boot Mode to CD
2. Boot server/VM from Linux CD
3. Hit F5 to enter Rescue Mode.
Disable NetworkManager on Redhat 6.x
The Network Manager service is currently enabled by default on Red Hat Enterprise Linux installations where one of these package groups was selected during installation:
Desktop
NM_CONTROLLED will be installed so that your network interface be managed the NetworkManager daemon. This means the traditional means of managing your network interfaces via the /etc/sysconfig/network-scripts/ifcfg-ethX files will no longer work. Thus, our problem.
BIND DoS vulnerability CVE-2015-5477 – Security fix for in CentOS, RedHat, Debian and Ubuntu Servers
Vulnerability Issue:
A flaw was found in the way BIND handled requests for TKEY DNS resource records. A remote attacker could use this flaw to make named (functioning as an authoritative DNS server or a DNS resolver) exit unexpectedly with an assertion failure via a specially crafted DNS request packet.
GHOST Vulnerability (glibc)
On January 27, 2015, the GHOST vulnerability was announced by Qualys. This vulnerability allows remote attackers to take complete control of a system by exploiting a buffer overflow bug in a glibc function GetHOST. This vulnerability should be considered serious and all affected servers should be patched immediately.
Generating a Certificate Signing Request (CSR)
To generate your CSR, you will need to log in to your server and use the OpenSSL software to generate a CSR and private key.
- Log in to your server, and enter the following command:
openssl req -nodes -newkey rsa:2048 -sha1 -keyout myserver.key -out server.csr
How to fix “Cannot setup NMI watchdog on CPUx” error on RHEL
When starting a RHEL Linux virtual machine, you see the message: Cannot setup NMI watchdog on CPU (2031297)
Symptoms
•When booting a RHEL virtual machine running with any hardware version, you see these messages echoed to the console:
How to install Samba package in CentOS 6.3 / RHEL
Install Samba package
Check and remove any previously installed samba package
[root@server ~]# rpm -qa | grep samba
[root@server ~]# yum list installed | grep samba
Install iftop on CentOS / RHEL
How to install and use iftop utility on Linux. This command listens to network traffic on a given interface (such as eth0 or eth1), and shows a table of current bandwidth usage by pairs of hosts.
Login as root, install iftop by the command below:
