Changing a specific value in a file using sed

/bin/sed -i.bak -e 's/^SELINUX=.*/SELINUX=disabled/g' /etc/selinux/config

Disable IPv6 on Linux

Sometime you may want to disable IPV6 on your Linux server. 

To check if IPV6 is running on your system
Run the following command.
#ifconfig  - This is show the ipv4 and ipv6 address

To disable ipv6
vi /etc/sysctl.conf

 Add the following lines at the bottom of the config file
net.ipv6.conf.lo.disable_ipv6 = 1
net.ipv6.conf.eth0.disable_ipv6 = 1
 
After saving the file, run the following command to apply the new changes.

#sysctl -p

To confirm the changes are applied, run the command
#ifconfig - This should not show ipv6 address any more
 

Securing Linux

Stop all unwanted services

#chkconfig --list |grep '3:on'

#chkconfig cups off

#chkconfig postfix off

#chkconfig atd off

#chkconfig ip6tables off

#chkconfig lvm2-monitor off

#chkconfig mdmonitor off

#chkconfig rpcidmapd off

#chkconfig nfslock off

#chkconfig mcelogd off

#chkconfig xinetd off

#chkconfig inetd off

Remove all unwanted packages

#rpm -e

Disable Root login

#vi /etc/ssh/sshd_config

PermitRootLogin no

#service sshd restart

Create a service account with Sudo Access

• Create a service account

#useradd

#passwd

(provide a strong password)

• Provide Sudo Access to service account _ In this case i have given all root access

#visudo

lbadmin ALL=(ALL)       ALL

Disable alt+ctrl+del key switch for reboot

#vi "/etc/init/control-alt-delete.conf"

Hash both the lines

#start on control-alt-delete

#exec /sbin/shutdown -r now "Control-Alt-Delete pressed"

Allow ssh access only from specific subnets or IP address

#vi /etc/hosts.allow

sshd:

#vi /etc/hosts.deny

sshd: ALL

 Restrict access to server for specific subnet.

# Generated by iptables-save v1.4.7 on Fri Jun 12 15:39:00 2015

*filter

:INPUT ACCEPT [75:5272]

:FORWARD ACCEPT [0:0]

:OUTPUT ACCEPT [68:5268]

-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

-A INPUT -p icmp -j ACCEPT

-A INPUT -i lo -j ACCEPT

-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT

-A INPUT -p tcp -m tcp --dport 80 -j ACCEPT

-A INPUT -p tcp -m tcp --dport 443 -j ACCEPT

-A OUTPUT -p udp --dport 123 -j ACCEPT

-A INPUT -p udp --sport 123 -j ACCEPT

-A OUTPUT -p tcp --dport 123 -j ACCEPT

-A INPUT -p tcp --sport 123 -j ACCEPT

-A INPUT -j REJECT --reject-with icmp-host-prohibited

-A FORWARD -j REJECT --reject-with icmp-host-prohibited

COMMIT

Set IP tables to start at reboot

#chkconfig iptables on

Apply the new IP table rules by running command

#service iptables start

Check all accounts have password set to them. No account should be without password less loging

grep -v ':x:' /etc/passwd

Cannot initiate the connection to 80:80 (0.0.0.80)

When running apt-get update command, if you receive the below mentioned error

W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/restricted/i18n/Translation-en_US  Cannot initiate the connection to 80:80 (0.0.0.80). - connect (22: Invalid argument)

Edit the following file
vi /etc/apt/apt.conf

Hash out the following entry
#Acquire::http::Proxy "ProxyIP:ProxyPort";


Now try #apt-get update, this should update the repository informaiton

View database output in tabular format

mysql -u root -p 

mysql>\P less -S

Create USB Boot disk for different flavours of operating system.

Create USB Boot Disk for different flavours of OS

Windows 8 and Windows 2012 rebooting issue on Proxmox VM

When you boot any VM and try to install Windows 8 or Windows 2012, the VMs will go into a continuous reboot. This is due to the missing CPU flag settings.

To fix this issue modify the VM configuration file of the VM

cd /etc/pve/qemu-server
vi 106.conf  ( Assuming 106.conf is the VM on which you are installing Win8 or Win2012)

balloon: 1024
bootdisk: ide0
cores: 2
args: -cpu qemu64,+sep,+cx16,+lahf_lm
ide0: PROXMOX6_VMVOL:106/vm-106-disk-1.qcow2,format=qcow2,size=32G
ide2: ISO:iso/Windows_8.1_x64.iso,media=cdrom,size=5227698K
memory: 2048
name: OPSI-Windows8
net0: virtio=DA:3B:63:57:3C:6F,bridge=vmbr0,tag=103
ostype: other
sockets: 1