Linux Classroom notes 30/July/2026

ssh

• username and password
• username and pravite key file ssh -i ~/Downloads/github.pem ubuntu@34.229.212.219 ssh -i <path of pemfile> username@ipaddress

create user and allow password auth

sudo adduser dev

## Edit file and add password auth yes
sudo nano /etc/ssh/sshd_config.d/50-cloudimg-settings.conf

PasswordAuthentication yes

sudo systemctl restart ssh

ssh username@ipaddress

scp -r ~/data dev@34.229.212.219:/home/dev/
dev@34.229.212.219's password: <enter password>
auth.log                                                    100%   52KB 120.8KB/s   00:00
data.txt                                                    100%   27     0.1KB/s   00:00


## output
dev@ip-172-31-41-244:~$ ls
data

• To create pemfile
  • ssh-keygen
• copy public file to linux machine
  • cat ~/.ssh/id_ed25519.pub | ssh -i ~/Downloads/github.pem ubuntu@34.229.212.219 "mkdir -p ~/.ssh && chmod 700 ~/.ssh && cat >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys"

SCP (secure copy portocal)

• scp source desc
  • scp -i ~/Downloads/github.pem data.txt ubuntu@34.229.212.219:/home/ubuntu/
  • scp data.txt ubuntu@34.229.212.219:/home/ubuntu/scp/
• Donload files from remote
  • scp -i ~/Downloads/github.pem ubuntu@34.229.212.219:/var/log/auth.log .
  • scp -r -i ~/Downloads/github.pem ~/data ubuntu@34.229.212.219:/home/ubuntu/

sftp : secure file transver protocal:

sftp> ls                     # list remote directory
sftp> lls                    # list local directory
sftp> cd /path/to/dir        # change remote directory
sftp> lcd /path/to/dir       # change local directory
sftp> pwd                    # print remote working directory
sftp> lpwd                   # print local working directory
sftp> get file.txt           # download file from remote to local
sftp> get -r remote_dir      # download directory recursively
sftp> put file.txt           # upload file from local to remote
sftp> put -r local_dir       # upload directory recursively
sftp> mkdir new_dir          # create remote directory
sftp> rmdir old_dir          # remove remote directory
sftp> rm file.txt            # delete remote file
sftp> rename old.txt new.txt # rename remote file
sftp> chmod 755 file.txt     # change remote file permissions
sftp> exit                   # close the sftp session