Linux Grundlagenhandbuch
Common Commands
Help Commands
| Command |
Description |
| compgen -c | Show all commands |
| compgen -a | Show all alias commands |
| compgen -A function | Show available functions |
| man <command> |
Show manual page of a command (more info than --help) |
| <command> --help |
Show help page of a command (less info than man command) |
| <command> --version |
Show version of a command |
File & Folder Commands
| Command | Description |
| ls -lah |
List files/folders in current directory (+infos) |
| mkdir newdir |
Create a new folder |
| cd somefolder |
Change/switch to another directory |
| cd /mnt/ | change/switch to another drive |
| cp file.txt file-copy.txt |
Copy a file |
| mv file.txt file-renamed.txt |
Rename a file |
| mv file.txt /tmp |
Move file to another folder |
| rm file.txt |
Remove a file |
| rm -rf folder |
Remove entire folder (recursive) |
| ln -s original target |
Create a symlink |
| pwd |
Show path of current folder |
| chown <arguments> <user>:<group> file.txt |
Change Owner and Group of file (use -R for rekursive) |
Search & String Commands
| Command | Description |
| find . -name "file.txt" |
Search for a file (recursive) |
| find . -name "*.txt" |
Search for all txt files |
| grep -rin "search string" |
Search for a string in current folder (recursive) |
| grep -rin "search string" | cut -c 1-100 |
Search for a string in current folder + limit output of string |
| sed -Ei 's/someString/newString/g' file.txt |
Replace "someString" with "newString" in a file |
| head file.txt |
Show first 10 lines of file |
| tail file.txt |
Show last 10 lines of file |
| cat file.txt |
Show full content of file |
| cat file.txt | grep "search string" |
Pipe output of "cat" command to grep + filter string |
Terminal Search, Shortcuts & Autocompletion
| Command | Description |
| Ctrl + a | Jump to beginning of line |
| Ctrl + e | Jump to end of line |
| Ctrl + Arrow Left |
Jump word backward |
| Ctrl + Arrow Right |
Jump word forward |
| Ctrl + w | Remove word backward |
| Alt + w |
Remove word forward |
| Ctrl + p |
Go through command line history backward |
| Ctrl + n |
Go through command line history forward |
| Ctrl + r |
Reverse Search in command history: - Type in something to search - Type Enter to execute the searched command - Type "Ctrl + r" to search further in reverse - Type "Ctrl + s" to search further in inverse - Tip: In only a few cases it makes sense to use the inverse search (Ctrl + s) from the beginning, but usually you want to search in reverse from the latest history commands |
| Ctrl + s |
Same as "Ctrl + r" but inverse (starts from the beginning of the history) |
| Ctrl + f |
Autocomplete a suggestion (Fish Shell only) |
OS Helper Commands
| Command | Description |
| du -csh . |
Show size of current folder |
| df -h |
Show partitions / drives |
| lsb_release -a |
Show OS Version / Informations |
Remote / Host Commands
| Command | Description |
| wget https://www.somewhere495848.com/test.txt |
Download a file |
| curl -LI https://www.google.com |
Show Header Informations of URL |
| whois <host> |
Show NS, DNS, Register about a host (e.g.: whois google.com) |
| host <host> |
DNS Lookup of a host (e.g.: host google.com) |
| dig <host> |
DNS Lookup of a host (verbose) (e.g.: dig google.com) |
| rsync -avz myfolder somehost:/var/www/ |
Sync a folder to a remote host and specific path |
| rsync -avz somehost:/var/www/ . |
Sync from remote host and specific path to local folder |
| rsync -avz <dirSource> <dirTarget> | Sync entire Folder (locally) |
| rsync -avz <dirSource>/ <dirTarget> | Sync only contents of folder (locally) |
Command-Line Operators
| Command | Description |
| <command> > file.txt |
Write output of a command into a file (creates/overwrites file) |
| <command> >> file.txt |
Write output of a command into a file (appends at end of file) |
| <command1> && <command2> |
Do command2 only if command1 succeeds |
| <command1> || <command2> |
Do command2 only if command1 fails |
| <command1> | <command2> |
Pipe command1 output into command2 |
| ! |
Negation Operator (e.g. find . ! -user "root") |
| More about operators: linux-command-operators |
Other helpful Commands
| Command | Description |
| bash myCustomScript.sh |
Execute a bash script |
| history | tail |
Show last 10 lines of your history (commands) |
| htop |
Very helpful utility to show all process, cpu, ram, .. |
| ps aux | grep http |
Show processes who accesses http |
| which <command> |
Show path location of a command |
| tar -cvf myfolder.tar myfolder |
Create a compressed tar file of a folder |
| tar -xvf myfolder.tar |
Extract a compressed tar file |
| zip -r myfolder.zip myfolder |
Create a compressed zip file |
| unzip myfolder.zip |
Extract a compressed zip file |
| EDITOR=nano crontab -e | Set Editor for current shell only (temporarily) |
| select-editor | Set Editor for user (usually permanently) |
| vim file.txt | Edit a file in the Vim Editor |
| nano file.txt | Edit a file in the Nano Editor |
|
sudo su - www-data -s /bin/bash
|
Switch User to example "www-data" |
SSH Setup & Security
SSH File Structure
| File-/Folder Structure |
Description |
Security |
| ~ |
User Home Directory (e.g. ~ can be /home/username) |
|
| ~/.ssh |
SSH Ordner im Home Verzeichnis |
|
| ~/.ssh/config |
Erstelle einen neuen Host Eintrag in der ssh config, der Aufbau sollte wie folgt aussehen: |
|
| ~/.ssh/id_rsa |
Dein Private Key (niemals an andere übermitteln!!) |
|
| ~/.ssh/id_rsa.pub |
Dein Public Key (zum übermitteln an Dritte für Remote-Server Einrichtung) |
|
| ~/.ssh/authorized_keys |
Public Keys die Zugriff auf den aktuellen Host haben |
|
| ~/.ssh/known_hosts |
Einträge zu (trusted) Hosts (Einträge werden i.d.R. automatisch ermittelt und per User Prompt zur Bestätigung erfragt) |
|
SSH Commands
| Command |
Description |
| ssh someHostAliasName |
Connect to a host from your ~/.ssh/config |
| ssh-keygen -t rsa -b 4096 -C "your_email@example.com" | Create a 4096Bit encrypted SSH Key |
| ssh-copy-id someHostAliasName |
Copies your current ssh pub key to a remote host (Alternatively connect to the ssh host and add your public key content to the file ~/.ssh/authorized_keys) |
| ssh -Tv git@github.com | Analyze if a ssh connection is possible to a host (e.g. git@github.com) |
| ssh -o PubkeyAuthentication=no -o PreferredAuthentications=password someHostAliasName | Check if a host allows password authentication |
SSH Hardening:
This hardens SSH + Disables Root Access (do this only if you know what you are doing!!)
Edit sshd_config (e.g. vim /etc/ssh/sshd_config) and change/add the following:
PermitRootLogin no # or "prohibit-password"
PubkeyAuthentication yes
PasswordAuthentication no # or use Match Blocks instead (see: https://ostechnix.com/disable-ssh-password-authentication-for-specific-user-or-group/)
PermitEmptyPasswords no
ChallengeResponseAuthentication no
UsePAM no
X11Forwarding no
# Optional:
# Match User app-*
# PasswordAuthentication yes
#
# Match User admin-*
# PasswordAuthentication no
After changing the file restart the ssh service: systemctl restart sshd and verify if you are still able to connect (use a different user than root)!
Cronjobs
Default PHP-Script Aufruf:
*/5 * * * * [path/to/php] [absPath/to/script]PHP-Script Aufruf mit env Variable:
e. g. * * * * * TYPO3_CONTEXT=Development/Server /[absPathToPHP]/php7.4-cli -f ~/[absPath]/typo3/sysext/core/bin/typo3 scheduler:run
*/5 * * * * [ENV-Variable] [path/to/php] [absPath/to/script]