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Pemecahan Masalah

Panduan mengatasi masalah umum pada server ujian.

Service Tidak Jalan

Nginx gagal start

# Cek error
systemctl status nginx
nginx -t

# Error umum: "port already in use"
lsof -i :80
lsof -i :443
# Kill proses yang menggunakan port tersebut

# Error umum: "SSL certificate not found"
ls -la /etc/nginx/ssl/
# Pastikan file .crt dan .key ada dan readable

PHP-FPM gagal start

# Cek error
systemctl status php8.3-fpm
journalctl -u php8.3-fpm --no-pager -n 50

# Error umum: "pool ujian cannot get uid"
id www-data
# Jika user tidak ada: apt install nginx (creates www-data)

# Error umum: "unable to bind listening socket"
ls -la /run/php/
# Pastikan direktori /run/php/ ada
mkdir -p /run/php && chown www-data:www-data /run/php

MariaDB gagal start

# Cek error
systemctl status mariadb
journalctl -u mariadb --no-pager -n 50

# Error umum: disk penuh
df -h /var/lib/mysql/
# Bersihkan disk atau expand partition

# Error umum: InnoDB corruption
# JANGAN hapus ib_logfile* sembarangan
# Backup dulu, lalu:
examtool backup-db

Memcached gagal start

systemctl status memcached
# Biasanya masalah port conflict atau RAM tidak cukup
free -m

Masalah Koneksi

Tidak bisa akses dari browser

  1. Cek DNS: nslookup ujian.fk.example.ac.id
  2. Cek firewall: ufw status
  3. Cek nginx: systemctl status nginx
  4. Cek SSL: openssl s_client -connect ujian.fk.example.ac.id:443
  5. Cek log: tail -20 /var/log/nginx/ujian_error.log

ERR_CONNECTION_REFUSED

  • Port 443 tidak dibuka di firewall
  • Nginx tidak running
  • Cek: ufw allow 443/tcp && systemctl restart nginx

ERR_SSL_PROTOCOL_ERROR

  • Certificate dan key tidak match
  • Certificate expired
  • Cek: openssl x509 -in /etc/nginx/ssl/ujian.crt -noout -dates

502 Bad Gateway

  • PHP-FPM tidak running
  • Socket file missing
  • Cek: systemctl restart php8.3-fpm
  • Cek: ls -la /run/php/php8.3-fpm-ujian.sock

504 Gateway Timeout

  • PHP script timeout (query berat)
  • Cek slow query: tail -20 /var/log/mysql/slow-query.log
  • Tambah timeout sementara di nginx config

Masalah Database

Koneksi database gagal

# Test login manual
mysql -u usr_kedokteran -p cbt_kedokteran

# Cek MariaDB running
systemctl status mariadb

# Cek socket
ls -la /run/mysqld/mysqld.sock

# Reset password jika lupa
examtool reconfigure

Database lambat

# Cek slow queries
tail -50 /var/log/mysql/slow-query.log

# Cek table lock
mysql -e "SHOW PROCESSLIST;"

# Cek ukuran database
mysql -e "SELECT table_schema, ROUND(SUM(data_length+index_length)/1024/1024,2) AS 'Size (MB)' FROM information_schema.tables GROUP BY table_schema;"

Backup/Restore

# Backup
examtool backup-db
# File tersimpan di /var/backups/examtool/

# Restore
examtool restore-db --file=/var/backups/examtool/backup_2024xxxx.sql.gz

Masalah Performa

Server lambat saat ujian

  1. Cek resource: examtool status
  2. Cek RAM: free -m — jika swap terpakai banyak, RAM kurang
  3. Cek CPU: top — cek proses yang paling banyak makan CPU
  4. Cek disk I/O: iostat -x 1 5
  5. Cek koneksi: ss -s — berapa total koneksi aktif

OOM Killer

Jika server tiba-tiba mati/restart:

dmesg | grep -i "oom\|out of memory"
journalctl -k | grep -i oom

Solusi:

  • Kurangi jumlah client di konfigurasi
  • Tambah RAM server
  • Atau switch ke tier yang lebih kecil

Memcached tidak efektif

# Cek hit ratio
echo "stats" | nc localhost 11211 | grep -E "get_hits|get_misses"
# Hit ratio < 80% → cek konfigurasi cache di aplikasi

Masalah SSL

Certificate expired

# Cek expiry
openssl x509 -in /etc/nginx/ssl/ujian.crt -noout -dates

# Ganti certificate
cp /path/to/new.crt /etc/nginx/ssl/ujian.crt
cp /path/to/new.key /etc/nginx/ssl/ujian.key
nginx -t && systemctl reload nginx

Certificate chain tidak lengkap

Browser menunjukkan "Not Secure" meski certificate valid:

# Gabungkan certificate dengan chain
cat ujian.crt intermediate.crt > ujian-fullchain.crt
cp ujian-fullchain.crt /etc/nginx/ssl/ujian.crt
systemctl reload nginx

Masalah Fail2ban

IP admin ter-ban

# Cek IP yang di-ban
fail2ban-client status nginx-req-limit

# Unban IP
fail2ban-client set nginx-req-limit unbanip 192.168.1.100

# Whitelist IP di jail config
# Tambahkan ke ignoreip di /etc/fail2ban/jail.d/examtool.conf

Terlalu banyak false positive

Edit /etc/fail2ban/jail.d/examtool.conf:

  • Naikkan maxretry
  • Turunkan bantime
  • Tambahkan IP range ke ignoreip

Kemudian: systemctl restart fail2ban

Command Diagnostik

Kumpulan command untuk troubleshooting cepat:

# Status lengkap
examtool status

# Semua log error nginx (1 jam terakhir)
find /var/log/nginx/ -name "*error*" -mmin -60 -exec tail -20 {} \;

# Koneksi aktif
ss -tuanp | grep -E ":80|:443" | wc -l

# Disk usage
du -sh /var/www/* /var/lib/mysql/ /var/log/

# Proses PHP aktif
ps aux | grep php-fpm | grep -v grep | wc -l

# Restart semua service
systemctl restart nginx php8.3-fpm mariadb memcached