Group 1

Homeworks/Answer.md

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+# Framgia Training Workshop - Linux Essential 2
+## Homework answer (Group 1)
+
+### Homework 1  
+#### Question: "Why can a normal user change his/her password without root permission?"  
+#### Answer: Because the passwd command in installed setuid root:
+- Check permission of passwd command
+```
+$ ls -l /usr/bin/passwd
+-rwsr-xr-x 1 root root 41284 Sep 12  2012 /usr/bin/passwd
+```
+- The flag s(SUID) in the fourth position. This is a flag that can be set in the file permissions that tells Linux to assume the privileges of the user that owns the executable when it is run - in this case, root.
+
+### Homework 2
+```
+sudo groupadd framgia
+sudo chgrp framgia ~/shared_directory/
+sudo chmod g+s ~/shared_directory/
+umask 007 ; mkdir a_new_directory ; umask 117
+```
+### Homework 3
+#### Display line numbers
+`
+set number
+`
+#### Add support for Elixir language  
+- Plugin managers
+
+The most common plugin managers include [vim-plug][vim-plug],
+[NeoBundle][neobundle], [Vundle][vundle] and [pathogen.vim][pathogen].
+
+With pathogen.vim, just clone this repository inside `~/.vim/bundle`:
+
+`bash
+git clone https://github.com/elixir-lang/vim-elixir.git ~/.vim/bundle/vim-elixir
+`
+
+With the other plugin managers, just follow the instructions on the homepage of
+each plugin. In general, you have to add a line to your `~/.vimrc`:
+
+```viml
+" vim-plug
+Plug 'elixir-lang/vim-elixir'
+" NeoBundle
+NeoBundle 'elixir-lang/vim-elixir'
+" Vundle
+Plugin 'elixir-lang/vim-elixir'
+```
+
+- Manual installation
+
+Copy the contents of each directory in the respective directories inside
+`~/.vim`.
+#### set default list of file encoding: `utf-8`, `shift-js`, `sjis`, other encoding.
+`set fileencodings=utf-8,shift-js,sjis`
+#### Disable arrow keys
+```
+noremap <Up> <Nop> 
+noremap <Down> <Nop> 
+noremap <Left> <Nop> 
+noremap <Right> <Nop> 
+```
+
+#### Replace tab with 4 spaces
+```
+set tabstop=4
+set shiftwidth=4
+set expandtab
+```
+
+### Homework 4
+```
+ssh-keygen -t rsa -C "" dev_rsa
+Host dev
+    HostName 128.45.53.123
+    Port 2222
+    User user_name
+       IdentityFile ~/.ssh/dev_rsa.key
+```
+### Homework 5
+no answer