FreeBSD - How to check what services or port opening in tcp/udp

Platform :
FreeBSD

How to :
List/show what services or port is listening/opening.

Installation :
The command comes with base system.

ssh - How to pipe output from local to remote server

In Bash, with pipe (the "|" symbol) and ssh makes a good combination of server administration tool, securely. Some examples :

FreeBSD - How to reset root account password

After the initial installation, the root password should be changed to a complicated enough password, then forget it. We're not suppose to use the root login & password as it might exposed to unnecessary risk. My preferred way of system administration should use sudo. It's more secure, controllable, and flexible.

But things happen. Today, I've totally forgotten root password. The box is lock out to the extend that only console access is allow. Worse of all, the regular password for the user name that I used to login for sysadmin stuff, have been "forgotten" as well too. Too Bad...

Anyway, as long as the physical box can be access, no security measures is good enough to stop the box being compromise. :P

This box is running the superior FreeBSD OS. The root password can be reset by :

FreeBSD - How to setup & configure jail with ezjail

OS virtualization is a technology that enable multiple copies of guest OS to run on top of a host OS. Why do we wanna do this?
- partition resources to share across multiple guest OS (current hardware to run multiple light guest OS. e.g. FreeBSD & Linux)
- enhance security (guest OS are isolated and thus hacking into a guest OS leaves other OS safe)
- saves power & money (hosting rack space & power are minimize)
- creating environments (application or OS testing, backup, legacy apps, admin delegation)
- improves server management (guest OS within virtualization are easier to move, copy, backup & remove)

FreeBSD Jail first appear in FreeBSD 4.x, introduced by Poul-Henning Kamp. Jail is a powerful OS virtualization that achieves security, cost, management & flexibility. Because of all these advantages, jail can some time be quite complex to setup & configure. Ezjail offers the simplicity to configure & maintain jails, without the complexity of getting our hands dirty. :p

Ezjail is a framework that controls jail. Ezjail takes care of the complicated part and makes setting up & maintenance of jail fun. Ezjail is develop by Dirk Engling, thanks Dirk. :)

FreeBSD jail does have its limitation. Here are the ones I've bump :
- resource control, e.g. ram & processor cannot be partition, they are all equally being shared. But hard disk space can be separate and control by implementing hard disk partition (or slice).
- all guest OS have to use the same kernel version as the host OS

Okay, enough of talking. Here's a simple step-by-step guide on how to setup Ezjail. Firstly, install Ezjail from sysutils/ezjail using Portmanager then proceed the below steps:

sudo - How to create another root (equivalent) account on linux or freebsd

The usual root account are meant for critical task, such as single user mode related operation. It hails the power of the system, as well the power of destruction (try "rm -rf /" :p). That's the reason why a lot of company have a policy to seal the root account or make some red tape so that one will give up requesting to use it. But sealing the root account will make daily routine system administration task difficult to execute.

No worries, sudo is the tool to clone another account with root privilege or control the access of critical command of a linux or BSD box. Every command that runs through sudo will be log to /var/log/auth.log.