Salin dan Bagikan

Linux System Administration Tutorial Pemula

Panduan Administrasi Sistem Linux untuk Pemula: User Management dan Permissions

Administrasi sistem Linux adalah skill fundamental yang harus dikuasai oleh setiap pengguna Linux, terutama yang menggunakan Linux untuk server atau development. Artikel ini membahas dasar-dasar administrasi sistem dengan fokus pada user management dan permissions.

User Management

1. Membuat User Baru

# Membuat user baru
sudo adduser username

# Atau dengan useradd (minimal)
sudo useradd -m username

# Set password
sudo passwd username

Perbedaan adduser dan useradd:

adduser: Interactive, user-friendly, membuat home directory dan setup default
useradd: Low-level, minimal, memerlukan opsi tambahan

2. Membuat User dengan Home Directory

# Dengan home directory
sudo useradd -m -d /home/username -s /bin/bash username

# -m: Create home directory
# -d: Specify home directory path
# -s: Specify default shell

3. Menambahkan User ke Groups

# Add user ke sudo group
sudo usermod -aG sudo username

# Add ke multiple groups
sudo usermod -aG sudo,docker,www-data username

# -a: Append (jangan lupa!)
# -G: Secondary groups

4. Mengubah User Properties

# Ganti username
sudo usermod -l newname oldname

# Ganti home directory
sudo usermod -d /new/home/dir -m username

# Ganti shell
sudo usermod -s /bin/zsh username

# Lock user
sudo usermod -L username

# Unlock user
sudo usermod -U username

5. Menghapus User

# Hapus user (keep home directory)
sudo userdel username

# Hapus user dan home directory
sudo userdel -r username

# Hapus dengan force (jika user sedang login)
sudo userdel -f username

6. Melihat Informasi User

# List semua users
cat /etc/passwd

# Cek user exists
id username

# Detail user
finger username
# atau:
getent passwd username

# User yang sedang login
who
w
last

Group Management

1. Membuat Group

# Membuat group baru
sudo groupadd groupname

# Dengan GID spesifik
sudo groupadd -g 1001 groupname

2. Mengubah Group

# Ganti nama group
sudo groupmod -n newname oldname

# Ganti GID
sudo groupmod -g 1002 groupname

3. Menghapus Group

sudo groupdel groupname

4. Melihat Group Information

# List semua groups
cat /etc/group

# Groups yang dimiliki user
groups username

# Primary group
id -gn username

# Semua groups
id username

File Permissions

1. Memahami Permission System

Struktur permission: -rwxrwxrwx

Position: 1234567890
         |---|---|---
          |    |    |
          |    |    +-- Others permissions
          |    +------- Group permissions
          +------------ Owner permissions

Tipe file:

-: Regular file
d: Directory
l: Symbolic link
c: Character device
b: Block device

Permission types:

r (read): 4
w (write): 2
x (execute): 1

2. Mengubah Permissions dengan chmod

# Numeric mode
chmod 755 file.txt    # rwxr-xr-x
chmod 644 file.txt    # rw-r--r--
chmod 600 file.txt    # rw-------
chmod 777 file.txt    # rwxrwxrwx (avoid!)

# Symbolic mode
chmod u+x file.txt    # Add execute for owner
chmod g-w file.txt    # Remove write for group
chmod o+r file.txt    # Add read for others
chmod a=r file.txt    # Set read-only for all

# Recursive
chmod -R 755 directory/

3. Mengubah Ownership dengan chown

# Ganti owner
sudo chown user file.txt

# Ganti group
sudo chown :group file.txt

# Ganti owner dan group
sudo chown user:group file.txt

# Recursive
sudo chown -R user:group directory/

# Copy ownership dari file lain
sudo chown --reference=file1.txt file2.txt

4. Mengubah Group dengan chgrp

# Ganti group
sudo chgrp groupname file.txt

# Recursive
sudo chgrp -R groupname directory/

Special Permissions

1. Setuid (Set User ID)

# Set setuid bit
chmod u+s /usr/bin/somebinary

# Numeric: 4
chmod 4755 /usr/bin/somebinary

# Check
ls -l /usr/bin/somebinary
# Output: -rwsr-xr-x

2. Setgid (Set Group ID)

# Set setgid bit pada file
chmod g+s file.txt

# Set setgid bit pada directory (new files inherit group)
chmod g+s directory/

# Numeric: 2
chmod 2755 directory/

# Check
ls -l directory/
# Output: drwxr-sr-x

3. Sticky Bit

# Set sticky bit (hanya owner bisa delete file di directory)
chmod +t /tmp

# Numeric: 1
chmod 1777 /tmp

# Check
ls -ld /tmp
# Output: drwxrwxrwt

Access Control Lists (ACL)

1. Install ACL

sudo apt install acl

2. Menggunakan setfacl

# Grant read+write untuk user spesifik
setfacl -m u:username:rw file.txt

# Grant read+execute untuk group
setfacl -m g:groupname:rx directory/

# Grant untuk everyone
setfacl -m o::r file.txt

# Recursive
setfacl -R -m u:username:rwx directory/

# Set default ACL untuk new files
setfacl -d -m u:username:rw directory/

3. Menggunakan getfacl

# View ACL
getfacl file.txt

# View directory ACL
getfacl directory/

# Remove ACL
setfacl -x u:username file.txt

# Remove all ACL
setfacl -b file.txt

System Maintenance

1. Disk Space Management

# Cek disk space
df -h

# Cek directory size
du -sh /path/to/directory

# Top 10 largest directories
du -h / | sort -rh | head -10

# Find large files
find / -type f -size +100M -exec ls -lh {} \; 2>/dev/null

# Cleanup package cache
sudo apt clean
sudo apt autoremove

2. Memory Management

# Cek memory usage
free -h

# Top memory consuming processes
ps aux --sort=-%mem | head -10

# Monitor dengan htop
htop

# Clear cache (hati-hati!)
sudo sync && echo 3 | sudo tee /proc/sys/vm/drop_caches

3. Process Management

# List processes
ps aux

# Tree view
ps auxf

# Cek process dengan resource tertinggi
top
htop

# Kill process
kill PID
kill -9 PID

# Kill by name
killall processname

# Nice level (priority)
nice -n 10 command
renice -n 10 -p PID

4. Log Management

# View system logs
sudo tail -f /var/log/syslog

# View authentication logs
sudo tail -f /var/log/auth.log

# Rotate logs manual
sudo logrotate -f /etc/logrotate.conf

# Journal logs (systemd)
journalctl -xe
journalctl -u servicename

System Monitoring

1. Uptime dan Load

# Uptime
uptime

# Load average
 cat /proc/loadavg

# CPU info
lscpu
cat /proc/cpuinfo

2. Network Monitoring

# Network connections
netstat -tulpn
ss -tulpn

# Bandwidth usage
iftop
nload

# Interface statistics
ip -s link

3. Scheduled Tasks

# List cron jobs
 crontab -l

# Edit cron
crontab -e

# System cron
ls /etc/cron.*
cat /etc/crontab

# View cron logs
grep CRON /var/log/syslog

Best Practices

1. Security

# Disable root SSH login
sudo nano /etc/ssh/sshd_config
# PermitRootLogin no

# Lock unused accounts
sudo usermod -L username

# Check for SUID files (potential security risk)
find / -perm -4000 -type f 2>/dev/null

# Check world-writable files
find / -perm -2 -type f 2>/dev/null

2. User Creation Checklist

# 1. Create user
sudo adduser username

# 2. Add to appropriate groups
sudo usermod -aG sudo,users,www-data username

# 3. Set password policy
sudo passwd username

# 4. Create home directory (automatic dengan adduser)

# 5. Copy default configs
sudo cp /etc/skel/.bashrc /home/username/
sudo cp /etc/skel/.profile /home/username/

# 6. Set ownership
sudo chown -R username:username /home/username

# 7. Test login
su - username

3. Regular Maintenance Script

#!/bin/bash
# maintenance.sh

echo "=== System Maintenance ==="

# Update
echo "Updating system..."
sudo apt update && sudo apt upgrade -y

# Cleanup
echo "Cleaning up..."
sudo apt autoremove -y
sudo apt clean

# Check disk space
echo "Disk space check:"
df -h

# Check failed services
echo "Failed services:"
sudo systemctl --failed

# Check logs
echo "Recent errors:"
sudo grep -i "error" /var/log/syslog | tail -5

echo "=== Maintenance Complete ==="

Troubleshooting

1. Permission Denied

# Check permissions
ls -la file.txt

# Check ownership
ls -l file.txt

# Fix ownership
sudo chown $USER:$USER file.txt

# Fix permissions
chmod 644 file.txt

# Check if account locked
sudo passwd -S username

# Check shell validity
cat /etc/shells
grep username /etc/passwd

# Check home directory exists
ls -ld /home/username

3. Command Not Found After User Creation

# Check PATH
echo $PATH

# Source profile
source ~/.bashrc
source ~/.profile

# Check shell
 echo $SHELL

Kesimpulan

Administrasi sistem Linux meliputi:

User Management: Membuat, mengubah, menghapus user accounts
Group Management: Mengelola group memberships
Permissions: Mengontrol access ke files dan directories
Special Permissions: Setuid, setgid, sticky bit
ACL: Access control untuk granular permissions
Maintenance: Disk, memory, process, dan log management

Menguasai konsep-konsep ini adalah dasar untuk menjadi Linux system administrator yang kompeten.

Panduan Administrasi Sistem Linux untuk Pemula: User Management dan Permissions

Panduan Administrasi Sistem Linux untuk Pemula: User Management dan Permissions

User Management

1. Membuat User Baru

2. Membuat User dengan Home Directory

3. Menambahkan User ke Groups

4. Mengubah User Properties

5. Menghapus User

6. Melihat Informasi User

Group Management

1. Membuat Group

2. Mengubah Group

3. Menghapus Group

4. Melihat Group Information

File Permissions

1. Memahami Permission System

2. Mengubah Permissions dengan chmod

3. Mengubah Ownership dengan chown

4. Mengubah Group dengan chgrp

Special Permissions

1. Setuid (Set User ID)

2. Setgid (Set Group ID)

3. Sticky Bit

Access Control Lists (ACL)

1. Install ACL

2. Menggunakan setfacl

3. Menggunakan getfacl

System Maintenance

1. Disk Space Management

2. Memory Management

3. Process Management

4. Log Management

System Monitoring

1. Uptime dan Load

2. Network Monitoring

3. Scheduled Tasks

Best Practices

1. Security

2. User Creation Checklist

3. Regular Maintenance Script

Troubleshooting

1. Permission Denied

2. User Cannot Login

3. Command Not Found After User Creation

Kesimpulan

Artikel Terkait