2022-04-01

Linux commands

Archive
Disk usage
Cronjobs
Network
SSH
Symlinks
System monitoring

Archive

Create a new compressed archive

  // c = create
  // z = compress gzip
  // f = file
  // v = verbose
  tar czfv new.archivew.tgz file.txt folder/

Extract archive

  // x = extract
  tar xzf ostechnix.tgz // in current directory
  tar xzf ostechnix.tgz -C output/path/ // in output path

Disk usage

List disk usage
```
  df -h
```
Show size of directory
```
  du -h /path/to/folder
```

Cronjobs

Edit current cronjobs
```
  sudo contab -e
```

Backup cronjobs

  sudo crontab -l > /some/shared/location/crontab.bak

Import cronjobs

  sudo crontab /some/shared/location/crontab.bak

Crontab job (generator / crontab-guru)

  # run script every 5 minutes and output the log into a file.
  */5 * * * * /home/user/script.sh >> /var/log/output.log

  # run script every 5 minutes without log file
  */5 * * * * /home/user/script.sh >/dev/null 2>&1

Network

Set mtu value for network device
```
  sudo ip link set dev eth0 mtu 1350
```

SSH

Generate a new ssh key

  ssh-keygen -t rsa -b 4096 -C "m@tthias.space"

Add ssh.pub key to remote system, to do password free login

  ssh-copy-id -f username@remoteHost
  ssh-copy-id -i path/to/key.pub -f username@remoteHost

Symlinks

Create a symlink

  ln -s /path/to/dir_or_file /path/to/new/symlink

Remove a symlink
```
  rm /path/to/new/symlink
```

System monitoring

Show disk usage
```
  df -h
```