# Users and Permissions Cheatsheet


## Create a user (called "ashley")

```
# useradd --create-home ashley
```


## Create a user in groups "users" and "dev"

```
# useradd --create-home --groups users dev ashley
```


## Create a user with the UID 1337

```
# useradd --create-home --uid 1337 ashley
```


## Create or change a user password

```
# passwd ashley
<enter password>
```


## Add user to a group ("coder")

```
# usermod --append --groups coder ashley
```


## Remove a user from a group ("coder")

```
# gpasswd --delete ashley coder
```


## Delete a user from the system

```
# userdel ashley
```


## Delete a user and all user data from the system

```
# userdel --remove ashley
```


## Show which users are currently logged in

```
# w
```


## Show login history

```
# last
```


## Set default permission of files to 644

```
# echo "umask 022" >> /etc/profile
```

## Set default permission of files to 664

```
# echo "umask 002" >> /etc/profile
```


## Change ownership of a file ("example.txt") to user ("ashley") 

```
# chown ashley:users example.txt
```


## Give read permission to user, group, and others

```
# chmod ugo+r example.txt
```


## Give write permission to user and group

```
# chmod ug+w example.txt
```


## Remove write permission to a file for group members

```
# chmod g-w example.txt
```


## Make a file executable

```
# chmod +x example.txt
```

## Log in as a different user 

```
# su - ashley
```

## Run a command ("ls") as a different user

```
# su - ashley --comand ls
```