[Linux & cli] Useful Linux command

Details

The following are some useful commands which usually made use and always being forgotten when needed, here is a note down.

• Edit /etc/fstab to mount new drives (files system, mount point, type, options, dump, pass)
• /dev/sdb1   /home/jacky/Documents/2tb-hdd   ext4   defaults  0   0
• mount -av (run from root, show the mount point)
• Run command and pipe all output to file
• do_something 2>&1 | tee -a some_file (2>&1 is to direct all stderr to stdout)
• Clear all text in a text file
• > someTxtFile.txt
• Kill process occupied by a known port (e.g. 32769)
• sudo kill -9 $(sudo lsof -t -i:32769)

References

• Reload fstab
  
• Linux Tutorial - 11. Piping and Redirection
  
• direct-stderr-and-stdout-in-bash
  
• Understanding crontab
  

[Chrome & Debug] Create and debug with test snippets in Chrome

Background

Very often it would be convenient and time consuming to have a fast setup and runnable js snippet playground to quickly test for the logic or debug etc.

Solutions

1. Open chrome

2. Right click "inspect" or press F12 shortcut

3. Navigate to "Sources"

4. At the left hand side panel, click the double right arrow, click "New snippet"

5. A snippet panel pops and you can freely write the test code

6. Press "Ctrl + Enter" to execute 

Frequently used git command

Details

There are some cases I need to use some specific git commands for some special purposes, like 

• Undoing git merge which haven't be pushed
• git reflog (Get the commit desired to return)
• git reset --hard sha
  
  
• Cherry-picking specific file changes from 1 commit to another
• git checkout <branch or sha of commit> -- filename
  
  
• Retrieve just 1 file from specific branch
• git checkout experiment -- app.js
  
  
• Show content changes which have been staged
• git diff --cached
  
  
• Show the diff of the same file between different commits of the same branch
• git diff HEAD^^ HEAD someFile (Show differences of someFile 2 commits before HEAD)
  
  
• Show file changes on specific commit (without diff information)
• git show --pretty="" --name-only {commit-sha}
  
  
• Show commits differences between 2 branches since branch created (file list)
• git log --oneline master..myBranch (Show changes since master branch)
• git log --oneline --no-merges master..myBranch (Show changes since master branch skipping merge commits)
  
  
• Get a list of branches created ordered with create date
• git branch --sort=-committerdate  # DESC
• git branch --sort=committerdate  # ASC
  
  
• Commit with standard input
• echo -e 'Update version number to v1.6.72.0\n\nfrom v1.6.70.0 to v1.6.72.0' | git commit /home/jacky/Documents/gitproj/p2_controller/docker/docker-compose-prod.yml /home/jacky/Documents/gitproj/p2_controller/docker/docker-compose-prod-upgrade.yml /home/jacky/Documents/gitproj/p2_controller/p2_controller/static_data/VERSION -F -

References

• Undo a Git merge that hasn't been pushed yet
• show commits since branch creation
• How to list all the files in a commit?
• How to cherry-pick changes from one file to another file?
• View git log without merge commits
• how-do-i-diff-the-same-file-between-two-different-commits-on-the-same-branch
• How to get just one file from another branch
• How can I get a list of Git branches, ordered by most recent commit?
  
• How do I show the changes which have been staged?

[Docker] Docker run emits "name is already in use" error

Background

When trying to docker run through docker compose, name is already in use appeared.

Solutions

Using docker ps -a, we will find there are docker containers created with the same name, it may due to docker compose stop not cleanly close all the containers.

To solve, find out, we can try to close all the running containers (you can find which one's name is duplicated, but I want to make life easier), docker stop $(docker ps -a -q), re-run the docker compose script again

References

• docker run --> 'name is already in use by container'
• https://coderwall.com/p/ewk0mq/stop-remove-all-docker-containers
• Docker error bind address already in use

[CSS] Meaning of margin:auto

Background

Sometimes we need to fulfill situation which we want to line up several components in a row and the last component leans on the right most of the div

Solutions

This comes to marginLeft/Right: auto, when we try to mark the container component with margin-left: auto, the container takes all the spaces available to the left hence position the switch button at the right most of the container.

That explains why when we left / right margin the DIV, we can center it at the center.

References

• What does margin auto mean?
  
• What is the meaning of `auto` value in a CSS property.
  

[JS] Onclick listener confusion in div inside div

Background

Sometimes we face situations when we have 2 layers of components (e.g. DIVs), while original (outer) div already configured with onclick listener but on top of the parent div, we also want the child div to have the same onClick listener.

Needless to say, the onclick action listener will be at the top will be fired first, and the parent one (underneath), which is not what we want, we want only child one to be detected and fired events

Solutions

This is related to event bubbling and event capturing. For event bubbling, clicking the inside DIV will trigger the event outside DIV, we need to stop both bubbling event and capturing event by e.stopPropagation and e.cancelBubble

References

• Howto: div with onclick inside another div with onclick javascript
• Binding and event handler — passing the event object
  
• React prevent event bubbling in nested components on click

Multiple accounts management in gitlab

Background

Having 2 different gitlab accounts one is for company and the other one is personal, I would like both work independently on the machine at home, pull source code separately with their corresponding username and repository.

Problems

Very often I encountered a situation with permission denied in my company account while listing the remote repository of do anything remote (like git pull), but I can only make my personal account work without success on my company account. Turns out git client is wrongly picking the my personal account ssh information to login to my working account causing the "permission right" error.

Solutions

1. Refer to ~/.ssh/config and update the config file, add 1 more ssh entry to my company gitlab account as follows

Host anywhere.gitlab.com
  PubkeyAcceptedKeyTypes +ssh-rsa
  HostName gitlab.com
  IdentitiesOnly yes
  IdentityFile ~/.ssh/id_rsa2
  User ihmcjacky

Host maxwellhk.gitlab.com
  PubkeyAcceptedKeyTypes +ssh-rsa
  HostName gitlab.com
  IdentitiesOnly yes
  IdentityFile ~/.ssh/id_rsa
  User maxwellhk

Here, we have 2 users, 1 is ihmcjacky for my company usage, another is for my private usage, HostName parameter both specified as gitlab.com, but the Host which is very important, it acts as an alias for git client to identify which configuration it should refer to when trying to login to gitlab. Name anything familiar to you. In my case anywhere.gitlab.com and maxwellhk.gitlab.com.

2. Go to the desired project (in my case, company repository), navigate to .git folder and open config, configure the username and user email manually so as to let git client not to use globally configured settings for log in. Also in remote-origin url settings, configure as follows

url = git@anywhere.gitlab.com:p2Firmware/p2_controller.git

The anywhere.gitlab.com here is important, it is the alias we specified in ~/.ssh/config.

For safety, we can follow References > Multiple SSH keys for different accounts on Github or Gitlab, go through the processes, delete the cached keys and add back the ssh entries and check the ssh connection

3. Finally, add back the new origin URL to the project by using git remote set-url origin new.git.url/here

References

• Git pushing to remote GitHub repository as wrong user
  
• Multiple SSH keys for different accounts on Github or Gitlab
  
• Configure SSH to a different directory
  
• https://medium.com/uncaught-exception/setting-up-multiple-gitlab-accounts-82b70e88c437