Table Of Content

• Installation and settings
  • Set prompt (提示；提詞)
    • For GIT
  • Shell
    • bash-it
  • Set Display to XQuartz
• Use
  • Terminal
    • Backspace becomes Space key in GDB
  • Editors
  • Remotely connect the server from MAC OS X
    • by iTerm2
  • SSH
    • Run graphical programs remotely
    • SSH ProxyCommand example: Going through one host to reach another server
  • Free up Space
    • Check use percentage of mounted devices
  • Migrate or Back home directory
  • File manipulation
    • Replace string in file
    • Create and Extract .tar.bz2 or .tar.gz files
  • Network checking
    • Get routing path
• Information
  • Directory structure
• Coding
  • Linux kernel coding style
  • 8) commenting
• Plugins
  • fzf
    • Shell extensions
• FAQ
  • How to read man pages
• References

Installation and settings

建議使用 Ubuntu Linux 20.04 LTS (或版本更高的發行套件)，Linux 核心必須在 v5.4 以上，否則課程提供的範例和作業無法正確執行。

• Try installation on Apple MacBook by multipass project

  • 步驟 from teacher:
    brew install multipass # 安裝套件

    multipass launch -c 2 -d 10G -m 2G -n ubuntu # 建立名為 ubuntu 的虛擬機器環境，其中 -c 表示 CPU 數量、-d 表示儲存裝置的容量、-m 表示主記憶體空間

    multipass shell ubuntu # 一旦上述的虛擬機器環境建立，透過本命令即可存取到 Ubuntu Linux

    uname -a # 取得 Ubuntu Linux 核心版本資訊

    lsb_release -a # 取得 Distro資訊，如：Ubuntu release

• Update

  • On linux2022q1
    • Install the Ubuntu Linux along with macOS to my wife's MacBook Air 2014 Early
      • I followed the installation guide

        use a USB Flash Drive which has full permission to read or write, otherwise, Dual-Boot Manager may not recognize the Ubuntu image correctly.

Set prompt (提示；提詞)

For GIT

Reference the offical doc: A1.6 Appendix A: Git in Other Environments - Git in Bash

Points:

1. Copy the prepared scripts, git-completion.sh and git-prompt.sh from contrib/completion/. in Git repo somewhere handy

   I put them in my home directory: ~/Scripts

2. Note that to enclose the value assigned to PS1 by 'single quote', inorder to evaluate $(__git_ps1 " (%s)") correctly
   • Why?
   • The difference between 'single quote' and "double quote":

     reference QUOTING in man bash

     • Enclosing characters in single quotes preserves the literal value of each character within the quotes.
     • Enclosing characters in double quotes preserves the literal value of all characters within the quotes, with the exception of $, `, \, and, when history expansion is enabled, !.

Other references

• 6.9 Controlling the Prompt in the Bash Reference Manual
• Clear explaination in 4.7 Git prompt in ArchWiki

Shell

bash-it

installed plugins

• https://github.com/romkatv/gitstatus
• https://github.com/clvv/fasd

Set Display to XQuartz

https://www.reddit.com/r/osx/comments/y6e59/xquartz_and_apparently_incorrectly_set_display/

• Add the XQuartz to the Login Items
  

Use

Terminal

• 5 ways to navigate the Linux terminal faster
• Command Line Editing

Backspace becomes Space key in GDB

• Backspace, Tab not working in terminal (using ssh) Stack Exchange https://unix.stackexchange.com › questions › backspac…
• In the terminal, press Ctrl + v and press your backspace. You'll see what code is sent as "erase". … From iTerm (or another terminal app).
  Ctrl + v + Backspace –> ^?
• Help! Backspace Doesn't Work in the Linux Terminal
  Modern terminals use "Ctrl + ?" for Backspace. Most systems will recognize the latter as Backspace

Editors

• VIM

Remotely connect the server from MAC OS X

by iTerm2

• ls output does not have colors on different types
  Original:
  
  I google "iterm2 ssh no color", and was inspired from a solution:
  • Go to references window -> profiles -> Default -> Colors
  • Go to the list of Color Presets... and change the upper item from Solarized to Regular or High Contrast; the following picture shows the result of selecting Regular item:
    

SSH

Run graphical programs remotely

Ref.: How to install X Window System XQuartz on macOS for ssh X11 forwarding

• hung on executing the app after connecting server by ssh -Y the_server:

  • (guess): the localhost and the offset 11 were missed in my $DISPLAY
    • expected output:
      
    • output on my server:
      ​​​​​​[10:58] asahsieh@asahsieh-MacBookAir:~$ echo $DISPLAY
      ​​​​​​:0
      

    Try to update the environment variable $DISPLAY but the system still hung on the app

    but the issue is not the root cause, please check the next item

  • Try to debug on ssh

    ref.: X11 forwarding requested but DISPLAY not set

    • append vvv option
    • and I found my issue is the same as the question: X11 forwarding requested but DISPLAY not set

    Follow one of the answers, the points are:

    • Make sure the X11 display number
      –> Your DISPLAY on the local machine (*NOT* on the server side) is almost always :0.0
    • Make sure you can run X11 applications on your Mac alone first
      –> You may need to install XQuartz.
    • Execute ssh -X within xterm window from XQuartz

      updated: no need to do this step

• For better use

  1. no need to pass the -X option ssh command:
     Edit your ~/.ssh/config file:
     ​​​​​ForwardX11 yes
     

  2. you can run ssh in the background after running a GUI app as follows
     ​​​​​ssh user@server -f -X app-Name
     ​​​​​ssh nixcraft@nas01 -f -X gpass
     

• On virtual machine: Can-not-open-display-on-gitg

SSH ProxyCommand example: Going through one host to reach another server

Free up Space

Ref.:

• https://itsfoss.com/free-up-space-ubuntu-linux/
• https://www.fosslinux.com/2986/free-up-hard-disk-space-ubuntu.htm

• Use Stacer – GUI based System Optimizer

Check use percentage of mounted devices

df -h

Migrate or Back home directory

ref.: [Partitioning/Home/Moving](https://help.ubuntu.com/community/Partitioning/Home/Moving)

1. (Option) Mount an SD card

   How to Mount an SD Card in Linux
   How do I mount an SD card?

   • Ubuntu doesn't read SD Card after wake
     –> solve this issue by autofs?

2. Find the mount point for the SD card

   • by lsblk
     ​​​​​[13:10] asahsieh@asahsieh-MacBookAir:~$ lsblk
     ​​​​​NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
     ​​​​​loop0    7:0    0 131.8M  1 loop /snap/cmake/1035
     ​​​​​loop1    7:1    0 209.1M  1 loop /snap/code/91
     ​​​​​loop2    7:2    0  65.2M  1 loop /snap/gtk-common-themes/1519
     ​​​​​loop3    7:3    0 248.8M  1 loop /snap/gnome-3-38-2004/99
     ​​​​​loop4    7:4    0 110.8M  1 loop /snap/core/12725
     ​​​​​loop5    7:5    0  55.5M  1 loop /snap/core18/2344
     ​​​​​loop6    7:6    0  22.4M  1 loop /snap/universal-ctags/892
     ​​​​​loop7    7:7    0  61.9M  1 loop /snap/core20/1361
     ​​​​​loop8    7:8    0  55.5M  1 loop /snap/core18/2284
     ​​​​​loop9    7:9    0 323.5M  1 loop /snap/kde-frameworks-5-qt-5-15-core20
     ​​​​​loop10   7:10   0     4K  1 loop /snap/bare/5
     ​​​​​loop11   7:11   0 155.4M  1 loop /snap/firefox/1073
     ​​​​​loop12   7:12   0 242.3M  1 loop /snap/gnome-3-38-2004/76
     ​​​​​loop13   7:13   0   9.5M  1 loop /snap/htop/3359
     ​​​​​loop14   7:14   0   617M  1 loop /snap/libreoffice/242
     ​​​​​loop15   7:15   0  61.9M  1 loop /snap/core20/1376
     ​​​​​loop16   7:16   0  15.7M  1 loop /snap/universal-ctags/882
     ​​​​​loop17   7:17   0 110.7M  1 loop /snap/core/12821
     ​​​​​loop18   7:18   0  54.2M  1 loop /snap/snap-store/557
     ​​​​​loop19   7:19   0 625.3M  1 loop /snap/libreoffice/247
     ​​​​​loop20   7:20   0 295.7M  1 loop /snap/vlc/2344
     ​​​​​loop21   7:21   0 150.2M  1 loop /snap/okular/109
     ​​​​​loop22   7:22   0 155.3M  1 loop /snap/firefox/1115
     ​​​​​loop23   7:23   0  54.2M  1 loop /snap/snap-store/558
     ​​​​​sda      8:0    0   113G  0 disk 
     ​​​​​├─sda1   8:1    0   200M  0 part /boot/efi
     ​​​​​├─sda2   8:2    0  84.9G  0 part 
     ​​​​​└─sda3   8:3    0  27.9G  0 part /
     ​​​​​sdb      8:16   1 241.9G  0 disk 
     ​​​​​├─sdb1   8:17   1   200M  0 part 
     ​​​​​├─sdb2   8:18   1 120.8G  0 part /media/asahsieh/Transcend
     ​​​​​└─sdb3   8:19   1 120.7G  0 part /media/asahsieh/Ubuntu_data
     

   • or by fdisk -l

3. Move data by rsync command

Ref.: How to backup your home directory in Linux

File manipulation

Replace string in file

ref.: How to use sed to find and replace text in files in Linux / Unix shell

sed -i 's/search_string/replace_string/' filename

Create and Extract .tar.bz2 or .tar.gz files

Ref.: https://www.cyberciti.biz/faq/how-to-create-tar-gz-file-in-linux-using-command-line/#Creating_tar.gz_file

• Extract files
  • bz2
    tar -xvjf guitar_songs.tar.bz2
  • gz
    tar -xvzf ukulele_songs.tar.gz
• Create files
  • The syntax for the tar command is as follows:
    tar -czvf filename.tar.gz /path/to/dir1
tar -czvf filename.tar.gz /path/to/dir1 dir2 file1 file2
  • Create a tar.gz file from all pdf (".pdf") files
    tar -czvf archive.tgz *.pdf
  • To create projects.tar.gz in the current working directory, run:
    tar -czvf projects.tar.gz $HOME/projects/
    
    

Network checking

Get routing path

sudo mtr access.sifive.com -c 100 -r

Information

Directory structure

• Typical Ubuntu filesystem hierarchy
  
  

圖片出處: Filesystem Hierarchy Standard

• Filesystem Hierarchy Standard
  LSB Workgroup, The Linux Foundation

Coding

reference https://www.kernel.org/doc/html/latest/

Linux kernel coding style

8) commenting

Comments are good, but there is also a danger of over-commenting. NEVER try to explain HOW your code works in a comment:

• it’s much better to write the code so that the working is obvious, and it’s a waste of time to explain badly written code.

Generally, you want your comments to tell WHAT your code does, not HOW. Also, try to avoid putting comments inside a function body:

• if the function is so complex that you need to separately comment parts of it, you should probably go back to chapter 6 for a while.

When commenting the kernel API functions, please use the kernel-doc format. See the files at Documentation/doc-guide/ and scripts/kernel-doc for details.

The preferred style for long (multi-line) comments is:

/*
 * This is the preferred style for multi-line
 * comments in the Linux kernel source code.
 * Please use it consistently.
 *
 * Description:  A column of asterisks on the left side,
 * with beginning and ending almost-blank lines.
 */

For files in net/ and drivers/net/ the preferred style for long (multi-line) comments is a little different.

/* The preferred comment style for files in net/ and drivers/net
 * looks like this.
 *
 * It is nearly the same as the generally preferred comment style,
 * but there is no initial almost-blank line.
 */

There is no initial almost-blank line.

It’s also important to comment data, whether they are basic types or derived types.

• To this end, use just one data declaration per line (no commas for multiple data declarations).

  This leaves you room for a small comment on each item, explaining its use.

Plugins

fzf

Source: https://github.com/junegunn/fzf

Shell extensions

• Key bindings (CTRL-T, CTRL-R, and ALT-C) (bash, zsh, fish)
• Fuzzy auto-completion (bash, zsh)

FAQ

How to read man pages

Understanding man Pages in Linux [Beginner's Guide]

• check the format on terminal, e.g., SYNOPSIS:
  ​​$man man  
  ​​
  ​​The following conventions apply to the SYNOPSIS section and can be used as a guide in other sections.
  
  ​​bold text          type exactly as shown.
  ​​italic text        replace with appropriate argument.
  ​​[-abc]             any or all arguments within [ ] are optional.
  ​​-a|-b              options delimited by | cannot be used together.
  ​​argument ...       argument is repeatable.
  ​​[expression] ...   entire expression within [ ] is repeatable.
  

HOW TO READ MAN PAGES

• SYNOPSIS
  • words in [ ]: means flags for this command

References

• Linux handbook