Clear Ubuntu ‘bash’ history

After a lot of use, your history file can become full of a lot of old commands… once in a while, it can be useful (and safer) to clean them up.

NOTE: this can be especially important if you have ever used a password as a command line parameter as it is stored without encryption in a text file.


cat /dev/null > ~/.bash_history && history -c && exit

Also useful:

history -c
history -w


Install OpenSSH Server on Ubuntu

I’ve discussed the use of SSH in several posts in the past, but while recently building a new environment, I realized that I’ve never indicated how the service itself should be installed.


sudo apt-get install openssh-server

If you desire to change any of the default configuration such as port or cyphers…

sudo vi /etc/ssh/ssh_config

NOTE: If you intend to access the server from the Internet, you will have to verify that port forwarding is enabled on your routers and firewalls.


Comcast Business Class gateway forwarding port 22 for SSH

For as long as I’ve had Comcast, and other providers for that matter, I’ve been able to configure my internet gateway/router to allow port 22 (SSH) access to an internal machine. It came as a surprise to me earlier this week that I was blocked when I tried to use their web admin console to change the internal forwarding to a newer machine. As usual, Technical Support was less that helpful and said that it was not possible to do so, and never should have been as Comcast uses that port to administer the gateway. To make matters more disturbing, I was told that I could not have similar SSH access to the gateway, and that replacing their hardware, while permitted, would prevent my use of a static IP.

Back to the solution, as I know that I had only setup this forwarding about a year ago, and it was working only minutes before I tried to change it, I knew that the configuration was possible if I could figure out how it was being blocked. The message in the web console was a javascript alert(); and gave me a starting point. I opened up Firefox and used Firebug to look for the message. Here are a few interesting findings from:


var RemoteManagementPortsCgiBase = “8080,8080,1\|8181,8181,1\|2323,2323,1\|22,22,1\|”;

msg += “Public Port Range conflict with Remote Management Ports.\n”;

if (msg.length > 1)
return false;
return true;

If you even a little bit of javascript (or simple computer programming for that matter), the solution is clear…. if the ‘msg’ value is empty you will not see the alert or be prevented from making the change you desire.

Lesson to be learned by the Comcast developers (or most likely = subcontractors), always validate submitted form data in your application code, NEVER rely upon javascript alone to verify user entered data!

I also find it interesting that they are also preventing 8080, 8081 and 2323… perhaps that’s their other back doors in these gateways for their access. The same approach should work for those ports if you need it!

Colored terminal window text on Ubuntu (Linux)

After a clean install, or simply access to a new machine, I often find it helpful to enable colored prompts in the terminal/command line environment.
For standard Ubuntu / Debian / Linux environments, this only requires you to remove a comment from a single line in a config file.

In /home/%USERID%/.bashrc you will find the following text, the last line simply needs to have the hash removed:

# uncomment for a colored prompt, if the terminal has the capability; turned
# off by default to not distract the user: the focus in a terminal window
# should be on the output of commands, not on the prompt

Open vi/vim or your editor of choice and remove it and you are done!

NOTE: If you are using Nautilus, you will not see this file as it is hidden, choose “View”, “Show Hidden Files” (CTRL-H) and it should appear.