About

Imported from chaterm/terminal-skills (linux/user-permissions/SKILL.md). Install upstream with npx skills add chaterm/terminal-skills --skill user-permissions. Copyright stays with the author.

User and Permission Management

Name: user-permissions
Author: chaterm

Overview

Linux user management, group management, sudo configuration, ACL permissions and other skills.

User Management

View Users

# Current user
whoami
id

# User information
id username
finger username

# All users
cat /etc/passwd
getent passwd

# Logged in users
who
w
last                                # Login history

User Operations

# Create user
useradd username
useradd -m -s /bin/bash username    # Create home directory, specify shell
useradd -G group1,group2 username   # Specify supplementary groups

# Modify user
usermod -aG groupname username      # Add to group
usermod -s /bin/zsh username        # Change shell
usermod -L username                 # Lock user
usermod -U username                 # Unlock user

# Delete user
userdel username
userdel -r username                 # Also delete home directory

# Change password
passwd username
passwd -l username                  # Lock password
passwd -u username                  # Unlock password
chage -l username                   # View password policy

Group Management

View Groups

# User's groups
groups username
id -Gn username

# All groups
cat /etc/group
getent group

# Group members
getent group groupname

Group Operations

# Create group
groupadd groupname
groupadd -g 1001 groupname          # Specify GID

# Modify group
groupmod -n newname oldname         # Rename

# Delete group
groupdel groupname

# Manage group members
gpasswd -a username groupname       # Add user
gpasswd -d username groupname       # Remove user
gpasswd -M user1,user2 groupname    # Set member list

sudo Configuration

Basic Usage

# Execute as root
sudo command
sudo -i                             # Switch to root shell
sudo -u username command            # Execute as another user

# View permissions
sudo -l

sudoers Configuration

# Edit sudoers (recommended method)
visudo

# Or edit files under /etc/sudoers.d/
visudo -f /etc/sudoers.d/username

Common Configuration Examples

# /etc/sudoers.d/username

# Full privileges
username ALL=(ALL:ALL) ALL

# No password required
username ALL=(ALL) NOPASSWD: ALL

# Specific commands
username ALL=(ALL) /usr/bin/systemctl restart nginx

# Specific commands without password
username ALL=(ALL) NOPASSWD: /usr/bin/docker

# Group privileges
%groupname ALL=(ALL) ALL

ACL Permissions

View ACL

getfacl file
getfacl -R dir                      # Recursive view

Set ACL

# Set user permissions
setfacl -m u:username:rwx file
setfacl -m u:username:rx dir

# Set group permissions
setfacl -m g:groupname:rx file

# Set default ACL (new files inherit)
setfacl -d -m u:username:rwx dir

# Recursive set
setfacl -R -m u:username:rx dir

# Remove ACL
setfacl -x u:username file          # Remove specific
setfacl -b file                     # Remove all

Special Permissions

SUID/SGID/Sticky

# SUID (4) - Execute as file owner
chmod u+s file
chmod 4755 file

# SGID (2) - Execute as file group/directory inherits group
chmod g+s file
chmod 2755 dir

# Sticky (1) - Only owner can delete
chmod +t dir
chmod 1777 dir

# View
ls -la
# -rwsr-xr-x  SUID
# -rwxr-sr-x  SGID
# drwxrwxrwt  Sticky

Common Scenarios

Scenario 1: Create Developer User

# Create user and group
groupadd developers
useradd -m -s /bin/bash -G developers devuser

# Set password
passwd devuser

# Configure sudo
echo "devuser ALL=(ALL) NOPASSWD: /usr/bin/docker, /usr/bin/systemctl" > /etc/sudoers.d/devuser
chmod 440 /etc/sudoers.d/devuser

Scenario 2: Shared Directory Permissions

# Create shared directory
mkdir /shared
groupadd shared
chown root:shared /shared
chmod 2775 /shared                  # SGID ensures new files inherit group

# Add users to group
usermod -aG shared user1
usermod -aG shared user2

Scenario 3: Restrict User to Specific Commands

# /etc/sudoers.d/limited-user
limited ALL=(ALL) NOPASSWD: /usr/bin/systemctl status *, /usr/bin/journalctl

Troubleshooting

Problem	Solution
sudo permission denied	Check `/etc/sudoers.d/` configuration
User cannot login	Check shell, password lock status
Group permissions not working	Re-login or `newgrp groupname`
ACL not working	Check if filesystem supports ACL

Use it

Copy one of these into your project. Installing also returns the manifest and these snippets.

yaml

targets:
  - https://api.opensmartroute.ai/api/v1/registry/chaterm-terminal-skills-user-permissions/manifest   # or paste the manifest below

Manifest

An Open Capability Manifest: the router reads it to know what this does, what it costs and when to pick it.

chaterm-terminal-skills-user-permissions.ocm.jsonjson

{
  "ocm": "1",
  "id": "chaterm-terminal-skills-user-permissions",
  "kind": "skill",
  "name": "user-permissions",
  "description": "Linux user and permission management",
  "publisher": "chaterm",
  "version": "1.0.0",
  "capabilities": {
    "domains": [
      "general"
    ],
    "tags": [
      "skill-md",
      "linux",
      "user",
      "group",
      "sudo",
      "acl",
      "permissions",
      "skills-sh"
    ],
    "languages": [
      "en"
    ]
  },
  "quality_prior": 0.6,
  "examples": [
    "Linux user and permission management"
  ],
  "primary": false,
  "metadata": {
    "source": {
      "provider": "skills.sh",
      "repository": "https://github.com/chaterm/terminal-skills",
      "path": "linux/user-permissions/SKILL.md",
      "ref": "HEAD",
      "url": "https://github.com/chaterm/terminal-skills/blob/HEAD/linux/user-permissions/SKILL.md",
      "key": "chaterm/terminal-skills/linux/user-permissions/SKILL.md"
    }
  },
  "instructions": "# User and Permission Management\n\n## Overview\nLinux user management, group management, sudo configuration, ACL permissions and other skills.\n\n## User Management\n\n### View Users\n```bash\n# Current user\nwhoami\nid\n\n# User information\nid username\nfinger username\n\n# All users\ncat /etc/passwd\ngetent passwd\n\n# Logged in users\nwho\nw\nlast                                # Login history\n```\n\n### User Operations\n```bash\n# Create user\nuseradd username\nuseradd -m -s /bin/bash username    # Create home directory, specify shell\nuseradd -G group1,group2 username   # Specify supplementary groups\n\n# Modify user\nu",
  "cost": {
    "context_tokens": 1103
  }
}

Fetch it by URL: GET /api/v1/registry/chaterm-terminal-skills-user-permissions/manifest?version=1.0.0

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