You have an iso image and you want to boot from it without restarting the system, simply use qemu virtual machine as below (-m 512 says qemu will be use 512 Mb of RAM from system):

qemu -boot d -cdrom emu -m 512 -cdrom customcd.iso

qemu is slow when its compared with vmware or similar products, but it is easy to use and small, just use apt and it is ready in a few seconds later.

It is good to learn all the ip addresses which holds N+ tcp connection to your server. For example, if we want to list ip addresses and connection counts of hosts which has 25+ connection right now:

netstat -n --tcp --udp --numeric-hosts | \
grep -v 127.0.0.1 | \
awk '{if (/(tcp|udp)/) { print $5 }}' | \
sed 's/:.*//' | \
sort | \
uniq -c | \
sort -n | \
awk '{if ($1 > 25) {print "Count: "$1"\t"$2; }}'

and here is an example output:

Count: 26       92.80.103.61
Count: 27       77.246.104.149
Count: 35       88.232.169.103
Count: 44       88.226.7.150

If we want to list only the ip addresses, not the counter, change the last line as below:

awk '{if ($1 > 25) {print $2; }}'

You can use -h parameter to make df's output human readable as: df -h

-h parameter also can be used with ls to make ls' outputs human readable:

ls -h

To make a backup of your Master Boot Record, dd command helps us. For example, taking MBR backup of /dev/sda disc: dd if=/dev/sda of=/tmp/mbr.img bs=512 count=1