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
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.
HowTo Boot into Single User Mode – Ubuntu 12.04
Follow these steps to boot in Single User mode in Ubuntu 12.04:
Step 1: Reboot the server and press “shift” key continuously to get the grub loader screen.
Step 2: In the Grub2 menu, select the first line with Linux x.x.x.x-generic.
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 set up SSH keys authentication between hosts on Ubuntu
SSH keys allow authentication between two hosts without the need of a password. SSH key authentication uses two keys, a private key and a public key.
To generate the keys, from a terminal prompt enter:
How to stop / start / restart ssh on Ubuntu
How to install OpenSSH on Ubuntu
OpenSSH is a FREE version of the SSH connectivity tools that technical users of the Internet rely on. Users of telnet, rlogin, and ftp may not realize that their password is transmitted across the Internet unencrypted, but it is. OpenSSH encrypts all traffic (including passwords) to effectively eliminate eavesdropping, connection
How to flush iptables on Ubuntu
To see your current rules in iptables (IPv4), enter:
$ sudo iptables -L
To see your current rules in ip6tables (IPv6), enter:
How to stop and start ufw on Ubuntu
ufw command – This command is used for managing a Linux firewall and aims to provide an easy to use interface for the user.
Login as root.
