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1. Open a terminal window.

2. At the input prompt you will see this structure:
“`
nicholas@computer-name:~$ _
“`

3. So you have to edit the hostname file:
“`
sudo nano /etc/hostname
“`

4. When prompted, enter the administrator password and hit Enter.

5. The hostname file will open, showing the current computer name. Replace the name with the desired new name.

6. Hit Ctrl+X to save and exit.

7. New name will show when you open a new terminal window.

shot

What’s happening

One day, when I opened up terminal as usual, it showed [Process completed] and just terminated. I could not type any thing, run any scripts and work on my project. Even worse, this made me unable to install programs into my computer because many installations need to run shell scripts. Okay, I searched over the internet and there was no solution for that. I even peaked many parts in the Mac OSX system to see if there were any mis-configuration, of course nothing helps. After all, I though if there is nothing wrong, it must be  something done with my /bin/bash. And after I upgraded my bash, my lovely terminal came back!

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Change shell’s default execution

The truth is, when you open terminal, it execute /bin/bash. As it is not working now, we need another environment for us to execute stuff. Open “Terminal->Preference”, and change “Shells open with” manually to “/bin/sh”.

Change What Shell Opens

Update /bin/bash

Now we are going to download the latest version of bash and replace the old one. Open up a new terminal and now you are able to execute commands. Copy and paste the following codes into the terminal, they will automatically handle everything for you.

	curl -LO ftp://ftp.cwru.edu/pub/bash/bash-4.2.tar.gz
	tar zxvf bash-4.2.tar.gz
	cd bash-4.2
	./configure && make && sudo make install
	chsh -s /usr/local/bin/bash {user_name}
	sudo bash -c "echo /usr/local/bin/bash >> /private/etc/shells"
	cd /bin
	sudo mv bash bash-old
	sudo ln -s /usr/local/bin/bash bash
	
Once done

Go to “Terminal->Preference” again and change :Shells open with: back to “Default login shell”. Enjoy!

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[expand title=”Detailed explanations” tag=”h5″ trigclass=”arrowright”]

What I did?

Okay, I admit that I did something to the system sometimes ago. I was doing some experiments on “sandboxing” and played with “chroot jail” stuff before. That is, I need to create an environment with restricted support to the program I run. So I wrote a sandbox, configured it’s root to a ‘secure’ place (anywhere not the actual root), and copy essential executables to that new root. Well, so far I think I didn’t do anything harm to the system, but I might corrupt the /bin/bash when I copied it to the sandbox root.

Diagnosis

Shell will run the following files before letting user to do anything. Check everyone to see if there are any misconfigurations.

  • ~/.bash_profile (for /bin/bash)
  • ~/.profile (for /bin/sh)
  • /etc/profile (for /bin/sh)
  • /etc/bashrc (for /bin/bash)
  • (google for more)

To play with, add some echoes to see if they works. Btw, I love nano more than vi, so try out “sudo nano /etc/bashrc”.

Playing with Shell
Another thing

The code above updates your bash to version 4.2. To check if there is any new version, go to the ftp.
ftp://ftp.cwru.edu/pub/bash/

Reference

http://techscienceinterest.blogspot.com/2010/05/change-to-new-bash-shell-41-for-mac-os.html


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Caffeine has been a very useful app to instantly disable or enable the screensaver on mac. At least for me, I am using multiple computers in office and all of them except the one I am using will usually get idle. Getting into screensaver, however, is bad sometimes especially I was reading from that screen and type things on another screen, and not to mention the password input after the screen lock. Well anyway, I highly recommend it.

Mac

On mac, we can install it easily with the app store.

Ubuntu

But in ubuntu, it is not available on the software center. But you can still get it through command line. Turn on terminal and input the following one by one.

sudo add-apt-repository ppa:caffeine-developers/ppa
sudo apt-get update
sudo apt-get install caffeine

While using hit, it is really usual to have regrets on the commits done, especially the name used. In order to change those information in your repository, open terminal (or cmd in windows), go to the folder of your git repositoy, and run the following commands. Remember, replace “old_name”, “new_name” and “new@email.address” with your own information.

git filter-branch --commit-filter '
  if [ "$GIT_COMMITTER_NAME" = "old_name" ];
  then
    GIT_COMMITTER_NAME="new_name";
    GIT_AUTHOR_NAME="new_name";
    GIT_COMMITTER_EMAIL="new@email.address";
    GIT_AUTHOR_EMAIL="new@email.address";
    git commit-tree "$@";
  else
    git commit-tree "$@";
  fi' HEAD

Ssh is a very convenient way to remotely command or control other devices. We use ssh to push commits to git server, to access remote server, and even to manipulate the content of our iphones and ipads. However it’s usually distributing to type your long and elusive password every time. Therefore here I would like introduce a way to create a steady relationship between your computer and the remote server you wanna connect with.

The principle is this, ssh connection establishments requires verification using the computer unique key of both devices. in order to simplify this step, we can generate a public key of your computer in advanced and which allows other to identify you. While you put that public key in the remote device as authorized key, you can kinda fast forward the process.

step 1: open terminal and “ssh-keygen -t dsa”
step 2: open “.ssh/id_dsa.pub” and copy content inside
step 3: open new tab in terminal and ssh server
step 4: paste all content into /home//.ssh/authorized_keys

a@A:~> ssh-keygen -t rsa
a@A:~> ssh b@B mkdir -p .ssh
a@A:~> cat .ssh/id_rsa.pub | ssh b@B ‘cat >> .ssh/authorized_keys’

To merge 2 entirely unrelated branches or projects, we need to specify 0 as first revision in revision range. Turn on terminal (in Mac) or cmd (in Windows) and get to your project folder. Merge with the following shell script. merge -r0..-1 means to merge from revision 0 to the latest revision.

bzr merge [other_branch_location] -r0..-1

In Mac, Ruby is preinstalled. You can open Terminal and input the followings to view the version of Ruby installed in your Mac

ruby -v

Update Ruby. You might want to update your Ruby, however there is no installer for Ruby like Windows. Instead, we can use MacPort.

Step 1. Install MacPort. You can download from their website: macports.org or DMG Image of Version 1.9.1 for Snow Leopard

Step 2. Open “Terminal” and input command:

sudo port

Step 3. MacPort should be started after inputting your password, then input command:

install ruby

It is easy, isn’t it? You can check what you have installed, you can input this command in MacPort:

installed
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