# A few tips on managing Linux Servers

this will be a post on my collection of Linux commands which I find handy, in the various scenarios.

## Check for Operation System Information
```shell
hostnamectl
uname -r
free -m
top
htop 
``` 

## Investigate what are the listening ports
sometimes there is something already running on the port, that you're unable to start your program.. here's some way to find them.
```bash
sudo lsof -i -P -n
sudo lsof -i -P -n | grep LISTEN
sudo lsof -i :3000
kill -9 <PID>
```
## Some SU / SUDO Tips

- `sudo -i`  . (switch to root user)
- `sudo !!`  (execute the previous command as sudo)
- `su -`  sets up the shell environment as if it's new login
- `su`   just start shell as that user, use 'original user's environment settings.

and well... another tip `cd -` change directory back to the previous directory

## What if we want a User that act like the Root Id, at the meanwhile not using sudoer file?

this is another trick to set a account to be 'root' by changing its iD
`uname` check operating system 
list existing users view `/etc/passwd`
assign ID with root equivalent privileges by changing the current UID value of the new ID to UID=0

## Want a more efficient way to Copy files, Compare difference then only sync those?
Try rsync! 
Rsync is a useful utilities native to the linux environment. It has a parameter `n` to allow one to have dry-run session first to observe the verbose output.

A sample of a rsync command.
```shell
rsync -razvh --delete --exclude doc /data/source /data/destination
```
this runs recursive manner into the folder below, remove the files on the destination mirroring the source, and exclude target 'doc' pattern folder/files.

you could find more about this command from the manual or internet too. So something to consider along with `sftp, ftp, scp ... `

## What about sometimes we want to understand what a set of commands does?
just copy-paste the command onto https://explainshell.com/
I wish I would have discovered this earlier. My early days of learning the unix/linux command was to dig through the 'manual' from 'man' or 'help' to see what each parameter does and arguments are for.

![explainshell.jpg](https://cdn.hashnode.com/res/hashnode/image/upload/v1650993549235/DQ2qWC7BE.jpg)


I think this is not exhaustive list yet. just some of extract from my note. Perhaps you may share with me your favourite commands in linux in comment below too.