- Defined in `/etc/passwd` file
- name:password:UID:GID:GECOS:directory:shell
- name: `cbrown`
- password: `x`
- UID: `1000`
- GID: `1000`
- GECOS: [empty]
- directory: `/home/cbrown`
- shell: `/bin/bash`
```txt
root:x:0:0:root:/root:/bin/bash
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
...
cbrown:x:1000:1000::/home/cbrown:/bin/bash
```
---
# Group
- Defined in `/etc/group` file
- group_name:password:GID:members_list
- group name: `cbrown`
- password: `x`
- GID: `1000`
- members list: `woodstock`
- primary group membership not listed
```txt
root:x:0:
bin:x:2:
sys:x:3:
adm:x:4:cbrown
...
cbrown:x:1000:woodstock
```
---
# root
- Superuser privilege over the Linux
- UID: `0`
- GID: `0`
- Kernel bypasses some security checks for the user id number zero
---
# User and group details
whoami
id
groups
Print effective user name
Print real and effective user and group IDs
Print the groups a user is in