Add Change Default Shell For A User as a unix til.

README.md

@@ -221,6 +221,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 
 - [All The Environment Variables](unix/all-the-environment-variables.md)
 - [Cat A File With Line Numbers](unix/cat-a-file-with-line-numbers.md)
+- [Change Default Shell For A User](unix/change-default-shell-for-a-user.md)
 - [Check If A Port Is In Use](unix/check-if-a-port-is-in-use.md)
 - [Clear The Screen](unix/clear-the-screen.md)
 - [Create A File Descriptor with Process Substitution](unix/create-a-file-descriptor-with-process-substitution.md)

unix/change-default-shell-for-a-user.md

@@ -0,0 +1,15 @@
+# Change Default Shell For A User
+
+You can change the default shell program for a particular unix user with the
+`chsh` command. Just tell it what shell program you want to use (e.g. `bash`
+or `zsh`) and which user the change is for:
+
+```
+$ [sudo] chsh -s /usr/bin/zsh username
+```
+
+This command needs to be invoked with root privileges.
+
+This command updates the entry for that user in the `/etc/passwd` file.
+
+[source](http://superuser.com/questions/46748/how-do-i-make-bash-my-default-shell-on-ubuntu)