Others

Linux Commands

SSH

  • Create a .pem file on the virtual machine.
ssh-keygen -b 4096
cat .ssh/id_rsa.pub >> .ssh/authorized_keys
cp .ssh/id_rsa /home/your_user/your_key.pem
  • Copy the content of the .pem file to the local machine and use it with SSH.
ssh -p 22 -i "C:\Users\YUSHIANG.TSENG\.ssh\yushiang.pem" yushiangtseng@localhost

Unable to log in due to the error log message: SSH Authentication Refused: Bad Ownership or Modes for Directory.

  • View the log on the virtual machine: tail -f /var/log/auth.log
  • Resolve the issue by adjusting file permissions: 
    chmod go-w /home/your_user
chmod 700 /home/your_user/.ssh
chmod 600 /home/your_user/.ssh/authorized_keys

Text Editor - Vim

  • apt-get update
  • apt-get install vim
  • vim <filename> : open/create file
  • i : enter edit mode
  • Esc, type :x then Enter : exit vim

Monitor Logs

  • tail -f <filename> can continuously log file even it's changing.

File Transmit

  • scp -r <soure/path> <dst/path>
    • <soure/path>, <dst/path> : username@IP:path

Run in background - Screen

  • apt-get update
  • apt-get install screen
  • screen, type command, ctrl+a then d to exit
  • screen -ls: list all process
  • screen -r <process id>: enter running process

Fetch api - Curl

  • download file from link
curl "${download_link}" --output ${filename.extension}
  • test api
curl --location -g --request ${api_method} '${api_path}' \
--header 'Content-Type: application/json' \
--data-raw '{
 "key": "value", 
}'

Port - lsof

  • apt-get update
  • apt-get install lsof
  • lsof -i -P -n : print using ports

    For windows, use netstat -aof

Check available package version

  • apt update

  • apt-cache policy <packageName>

  • Example of getting available version of curl, then we can specify in dockerfile using RUN apt update && apt install curl=7.64.0-4+deb10u6 -y.
test@2023 ~ % docker run -it node:16.13.1-slim bash
root@795660af5321:/# apt update
Get:1 http://security.debian.org/debian-security buster/updates InRelease [34.8 kB]
Get:2 http://deb.debian.org/debian buster InRelease [122 kB]
Get:3 http://security.debian.org/debian-security buster/updates/main arm64 Packages [541 kB]
Get:4 http://deb.debian.org/debian buster-updates InRelease [56.6 kB]
Get:5 http://deb.debian.org/debian buster/main arm64 Packages [7737 kB]
Get:6 http://deb.debian.org/debian buster-updates/main arm64 Packages [8780 B]                                                                                    
Fetched 8500 kB in 19s (447 kB/s)                                                                                                                                 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
20 packages can be upgraded. Run 'apt list --upgradable' to see them.
root@795660af5321:/# apt-cache policy curl
curl:
  Installed: (none)
  Candidate: 7.64.0-4+deb10u6
  Version table:
     7.64.0-4+deb10u6 500
        500 http://security.debian.org/debian-security buster/updates/main arm64 Packages
     7.64.0-4+deb10u2 500
        500 http://deb.debian.org/debian buster/main arm64 Packages