id Command
Beginner User Management man(1)Print user and group IDs
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📅 Updated: Mar 15, 2026
SYNTAX
id [OPTION]... [USER]
What Does id Do?
id displays user and group identity information. Without arguments, it shows the current user's UID, GID, and all group memberships. With a username argument, it shows that user's information.
id is essential for verifying user identity, checking group memberships, debugging permission issues, and confirming that group changes took effect.
The output includes the numeric UID and GID along with their names, and all supplementary groups the user belongs to.
id is essential for verifying user identity, checking group memberships, debugging permission issues, and confirming that group changes took effect.
The output includes the numeric UID and GID along with their names, and all supplementary groups the user belongs to.
Options & Flags
| Option | Description | Example |
|---|---|---|
| -u | Print only effective user ID | id -u |
| -g | Print only effective group ID | id -g |
| -G | Print all group IDs | id -G |
| -n | Print name instead of number (with -u, -g, -G) | id -un |
| -r | Print real (not effective) ID | id -ru |
| username | Show info for specific user | id www-data |
Practical Examples
#1 Show current identity
Displays UID, GID, and all groups for the current user.
$ id
Output:
uid=1000(user) gid=1000(user) groups=1000(user),27(sudo),998(docker)
#2 Show specific user
Shows identity info for the www-data user.
$ id www-data
Output:
uid=33(www-data) gid=33(www-data) groups=33(www-data)
#3 Get username
Prints just the effective username.
$ id -un
Output:
user
#4 Get numeric UID
Prints just the numeric user ID.
$ id -u
Output:
1000
#5 List all groups
Lists all group names the current user belongs to.
$ id -Gn
Output:
user sudo docker www-data
#6 Check group membership
Checks if a user is in the sudo group.
$ id -Gn jdoe | tr " " "\n" | grep sudo && echo "Has sudo"Tips & Best Practices
Verify group changes: After usermod -aG, run id username to verify the group was added. The user must log out/in for groups to take effect in their session.
Real vs effective ID: Effective ID determines permissions. Real ID is the original user. They differ when running SUID programs or using sudo.
Current session vs stored groups: id shows stored groups from /etc/group. Your current session may differ until re-login. Use groups command for session groups.
Frequently Asked Questions
How do I check what groups I am in?
Use id -Gn for group names or id for full details. Or simply: groups.
How do I find a user UID?
Use id -u username for numeric UID, or id username for full identity information.
Why does id show a group but I still get permission denied?
Group changes require re-login. Log out and back in, or use newgrp groupname for the current session.
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