Linux use - HackMD

--- title: Linux use tags: linux --- :::spoiler Table Of Content [TOC] ::: # 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](https://multipass.run/docs/installing-on-macos?fbclid=IwAR32IXSEvGkjrWTdig7smGjm3Rnt3LFVFeSz3Nm1vsq_adInMrBsLGcgnPY) 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](https://support.apple.com/kb/SP700?locale=zh_TW) - I followed the [installation guide](https://www.lifewire.com/dual-boot-linux-and-mac-os-4125733) > :warning: **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](https://git-scm.com/book/en/v2/Appendix-A%3A-Git-in-Other-Environments-Git-in-Bash) :notes: 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](https://github.com/asahsieh/my-os-home-dir/tree/master/Scripts)* 2. Note that to enclose the value assigned to `PS1` by 'single quote', inorder to evaluate `$(__git_ps1 " (%s)")` correctly - [ ] Why? - :thinking_face: The difference between 'single quote' and "double quote": > reference [QUOTING](https://man7.org/linux/man-pages/man1/bash.1.html#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](https://www.gnu.org/savannah-checkouts/gnu/bash/manual/bash.html#Controlling-the-Prompt) in the `Bash Reference Manual` - Clear explaination in [4.7 Git prompt](https://wiki.archlinux.org/title/git#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 ![image](https://hackmd.io/_uploads/HyC3FuFjJe.png) # Use ## Terminal - [5 ways to navigate the Linux terminal faster](https://www.redhat.com/sysadmin/shortcuts-command-line-navigation) - [Command Line Editing](https://ftp.gnu.org/old-gnu/Manuals/gdb/html_chapter/gdb_toc.html#TOC242) ### Backspace becomes Space key in GDB - [Backspace, Tab not working in terminal (using ssh) Stack Exchange https://unix.stackexchange.com › questions › backspac...](https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjymfLHrsL-AhXFFogKHYVRDs4QFnoECBMQAQ&url=https%3A%2F%2Funix.stackexchange.com%2Fquestions%2F43103%2Fbackspace-tab-not-working-in-terminal-using-ssh&usg=AOvVaw1agSd98iXqkE_1hXeubtiD) - 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](https://www.makeuseof.com/backspace-not-working-in-linux-terminal/) Modern terminals use "Ctrl + ?" for Backspace. Most systems will recognize the latter as Backspace ## Editors - [VIM](/sfjW7NLjR9CGTfjEOCsqrQ) ## Remotely connect the server from MAC OS X ### by `iTerm2` - :notes: `ls` output does not have colors on different types *Original*: ![](https://hackmd.io/_uploads/Skh6_I01o.png) :bulb: I google "iterm2 ssh no color", and was inspired from [a solution](https://apple.stackexchange.com/a/51307): :::info - 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: ![](https://hackmd.io/_uploads/B1NJiLA1o.png) ::: ## SSH ### Run graphical programs remotely Ref.: [How to install X Window System XQuartz on macOS for ssh X11 forwarding](https://www.cyberciti.biz/faq/apple-osx-mountain-lion-mavericks-install-xquartz-server/) - :question: hung on executing the app after connecting server by `ssh -Y the_server`: - [x] :thinking_face: (guess): the `localhost` and the offset `11` were missed in my $DISPLAY - *expected output*: ![](https://www.cyberciti.biz/media/new/faq/2015/02/How-To-Set-Up-And-Use-X11-Forwarding-On-Linux-And-MacOS.png) - *output on my server:* ```shell [10:58] asahsieh@asahsieh-MacBookAir:~$ 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 [color=red] - [x] Try to debug on `ssh` > ref.: [X11 forwarding requested but DISPLAY not set](https://stackoverflow.com/questions/63626203/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](https://stackoverflow.com/a/64106469/3401549) 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](https://www.xquartz.org/). - ~~**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](https://www.cyberciti.biz//www.cyberciti.biz/faq/create-ssh-config-file-on-linux-unix/): ```shell ForwardX11 yes ``` 2. you can run ssh in the background after running a GUI app as follows ```shell ssh user@server -f -X app-Name ssh nixcraft@nas01 -f -X gpass ``` - :notes: *On virtual machine*: [Can-not-open-display-on-gitg](https://hackmd.io/@asahsieh/git#Can-not-open-display-on-gitg) ### [SSH ProxyCommand example: Going through one host to reach another server](https://www.cyberciti.biz/faq/linux-unix-ssh-proxycommand-passing-through-one-host-gateway-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](https://help.ubuntu.com/community/Partitioning)/[Home](https://help.ubuntu.com/community/Partitioning/Home)/[Moving](https://help.ubuntu.com/community/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](https://www.techwalla.com/articles/how-to-mount-an-sd-card-in-linux) > [How do I mount an SD card?](https://askubuntu.com/questions/95391/how-do-i-mount-an-sd-card) :::warning - [ ] [Ubuntu doesn't read SD Card after wake](https://askubuntu.com/questions/911078/ubuntu-doesnt-read-sd-card-after-wake) --> solve this issue by `autofs`? ::: 2. Find the mount point for the SD card - by `lsblk` ```shell [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` 4. Move data by `rsync` command > Ref.: [How to backup your home directory in Linux](https://www.pragmaticlinux.com/2021/05/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](https://www.cyberciti.biz/faq/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/` ![](https://hackmd.io/_uploads/SycG3N9tn.png) ## Network checking ### Get routing path `sudo mtr access.sifive.com -c 100 -r` # Information ## Directory structure - Typical Ubuntu filesystem hierarchy ![image alt](https://upload.wikimedia.org/wikipedia/commons/d/d6/Ubuntu_Filesystem_Hierarchy.png) > 圖片出處: [Filesystem Hierarchy Standard](https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard) - [Filesystem Hierarchy Standard LSB Workgroup, The Linux Foundation](https://refspecs.linuxfoundation.org/FHS_3.0/fhs/index.html) # Coding > reference [https://www.kernel.org/doc/html/latest/](https://www.kernel.org/doc/html/latest/) ## [Linux kernel coding style](https://www.kernel.org/doc/html/latest/process/coding-style.html) ## [8) commenting](https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting) :::info 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/](https://www.kernel.org/doc/html/latest/process/coding-style.html#commenting../doc-guide/index.html#doc-guide) and `scripts/kernel-doc` for details. The preferred style for long (multi-line) comments is: ```c /* * 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. ```c /* 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. */ ``` > :notes: 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 \[Beginner's Guide\]](https://itsfoss.com/linux-man-page-guide/) - check the *format* on terminal, e.g., `SYNOPSIS`: ```shell $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](https://www.cs.mcgill.ca/~guide/help/man.html) - SYNOPSIS - words in `[ ]`: means *flags* for this command # References - [Linux handbook](https://linuxhandbook.com/)