Things to do after installing Ubuntu

use snmpget to get linux cpu loading, etc

CPU Statistics

Load 1 minute Load: . 5 minute Load: . 15 minute Load: .

CPU percentage of user CPU time: . raw user cpu time: . percentages of system CPU time: . raw system cpu time: . percentages of idle CPU time: . raw idle cpu time: . raw nice cpu time: […]

Load balancing & NAT-ing multiple uplinks on Linux

LAN: eth0:

IP1: eth1:, gateway:

IP2: eth2:, gateway:

So here is how I would do by using iptables method:

Route tables

First edit the /etc/iproute2/rt_tables to add a map between route table numbers and ISP names

… 10 IP1 20 IP2 …

So table 10 and 20 is for ISP1 […]

Measure IOPs in Unix/Linux

IOPS = (MBps Throughput / KB per IO) * 1024 Or MBps = (IOPS * KB per IO) / 1024

CentOS/RHEL 6 virtualized guest tuning

1.yum install tuned tuned-utils

2. tuned-adm profile virtual-guest

3. dd if=/dev/zero of=tmpfile bs=1M count=1000

See the tables below :

Profile explanation :

default The default power-saving profile. This is the most basic power-saving profile. It enables only the disk and CPU plug-ins. Note that this is not the same as turning tuned-adm off, where […]

UEFI and Ubuntu

Use NOOP I/O Scheduler for virtualized Linux guest with kernel 2.6 guest on vmware

Refer to

The scheduler can be set for each hard disk unit. To check which scheduler is being used for particular drive, run this command:

cat /sys/block/disk/queue/scheduler

For example, to check the current I/O scheduler for sda:

# cat /sys/block/sda/queue/scheduler [noop] anticipatory deadline cfq

In this example, the sda drive scheduler is set to […]

Linux 2.6+ tuning for Data Transfer hosts connected at speeds of 1Gbps or higher

Nagios nrep “NRPE: Unable to read output” after using sudo

edit /etc/sudoers and comment the below :

#Defaults requiretty

Linux iptables firewall rules to prevent private IP leakage from masquerade/SNAT

Unroutable TCP type packets, from reserved for local use only networks (RFC1918), being sent out to internet on a Linux masquerade box.