4. Cron va vazifalarni rejalashtirish

🎯 Bu bobda nimani o'rganasiz:
cron asoslari — crontab, 5-maydon syntax
PATH muammosi — bashning eng ko'p uchraydigan cron tuzog'i
at — bir martalik kechiktirilgan vazifa
systemd timers — zamonaviy muqobil
flock — bir nusxa kafolati uchun production pattern
Real misol — Nightly backup notification bilan
⏱ Vaqt: ~25 daqiqa 🧪 Mashqlar: bashlings watch — 7 ta interaktiv mashq tayyor (exercises/14_cron/)

4.1. Nima uchun rejalashtirish kerak?

Server'ning kundalik avtomatik ishlari:

Vazifa	Tipik vaqt	Vosita
Database backup	har kecha	cron / systemd
Log rotation	har kun	logrotate (cron)
SSL sertifikat yangilash	oyiga 2 marta	certbot (cron)
Cache tozalash	har 15 daqiqa	cron
Health check & alert	har 5 daqiqa	cron / monitor
Index rebuild	dam olishlarda	cron

Asosiy g'oya

Inson ishtirokisiz, ishonchli, doimiy bajariladigan har vazifa — rejalashtirilgan vazifa. Mantra: "Agar oyiga ikkidan ko'p marta qilsang — avtomatlashtir."

4.2. `cron` asoslari

cron — Unix tizimlarining klassik scheduler'i (1975-yildan beri).

Asosiy buyruqlar

bash

crontab -l          # joriy ro'yxat
crontab -e          # tahrirlash (default editor ochiladi)
crontab -r          # ⚠ HAMMASINI o'chirish — diqqat!
crontab my.cron     # fayldan import
crontab -u ali -l   # boshqa foydalanuvchi cron'i (root sifatida)

Joylashuvlar

~/                          ← foydalanuvchi cron, `crontab -e` orqali
/var/spool/cron/<user>      ← cron'lar shu yerda saqlanadi (root only)
/etc/crontab                ← system-wide cron (user maydoni qo'shimcha)
/etc/cron.d/                ← qo'shimcha cron fayllar
/etc/cron.daily/            ← har kun ishga tushiriladigan skriptlar
/etc/cron.hourly/
/etc/cron.weekly/
/etc/cron.monthly/

crontab -r — diqqat!

-r flagi — butun cron jadvalingizni so'rovsiz o'chiradi. -i flagi yo'q!

Backup qilib qo'ying:

bash

crontab -l > ~/cron-backup-$(date +%F).txt

4.3. Cron syntax — 5 ta maydon

*  *  *  *  *  buyruq
│  │  │  │  │
│  │  │  │  └── hafta kuni      (0-7,  0 va 7 = yakshanba)
│  │  │  └───── oy              (1-12)
│  │  └──────── kun             (1-31)
│  └─────────── soat            (0-23)
└────────────── daqiqa          (0-59)

Maxsus belgilar

Belgi	Ma'nosi	Misol
`*`	har qiymat	`* * * * *` — har daqiqa
`,`	ro'yxat	`0,15,30,45 * * * *` — 15 daqiqa'da bir
`-`	diapazon	`9-17` — soat 9 dan 17 gacha
`/`	step	`*/5` — har 5 daqiqada
`*/N`	step bilan	`/15 * * *`

Real misollar

cron

# Har daqiqa
* * * * * /opt/heartbeat.sh

# Har 5 daqiqada
*/5 * * * * /opt/healthcheck.sh

# Har soat 0-daqiqasida
0 * * * * /opt/log-rotate.sh

# Har kun 02:00
0 2 * * * /opt/backup.sh

# Har yakshanba kecha 03:30
30 3 * * 0 /opt/weekly-report.sh

# Ish kuni 9-17 oraliqda har soat (1-5 = dushanba-juma)
0 9-17 * * 1-5 /opt/business-check.sh

# Har oyning 1-kunida 00:30
30 0 1 * * /opt/monthly-billing.sh

# Har 3 soatda
0 */3 * * * /opt/cache-refresh.sh

# Har 30 daqiqada, faqat ish kuni
*/30 * * * 1-5 /opt/sync.sh

Maxsus stringlar — `@`

String	Ekvivalent	Mazmuni
`@reboot`	(yuklanganda)	Tizim yuklanganida bir marta
`@yearly`	`0 0 1 1 *`	Yilda bir marta
`@monthly`	`0 0 1 * *`	Oyda bir marta
`@weekly`	`0 0 * * 0`	Haftada bir (yakshanba)
`@daily`	`0 0 * * *`	Kuniga bir
`@hourly`	`0 * * * *`	Soatiga bir

cron

@reboot   /opt/startup.sh
@daily    /opt/backup.sh
@hourly   /opt/cleanup.sh

Crontab generator

Murakkab sintaksis uchun — crontab.guru — interaktiv online tahlil. Ishonchli vosita.

4.4. Cron environment va PATH muammosi

Eng ko'p uchraydigan cron xato: "Skript terminalda ishlaydi, cron'da yo'q".

Sababi — cron muhitida PATH minimal:

cron

# Sodda ko'rinadi, lekin xato:
* * * * * mybackup.sh
# cron: `mybackup` topilmadi (PATH'da yo'q)

Cron PATH default

Aksariyat tizimda:

PATH=/usr/bin:/bin

Yo'q: /usr/local/bin, ~/bin, ~/.cargo/bin, ~/.local/bin va h.k.

Yechim — 3 yo'l

1. To'liq yo'l ishlatish (eng aniq):

cron

* * * * * /usr/local/bin/mybackup.sh

2. PATH'ni cron faylida o'rnatish:

cron

PATH=/usr/local/bin:/usr/bin:/bin
SHELL=/bin/bash

* * * * * mybackup.sh

3. Skript boshida PATH yuklash:

bash

#!/usr/bin/env bash
source ~/.bashrc   # yoki aniq:
export PATH="/usr/local/bin:/usr/bin:/bin"

# ... ish ...

Cron — interactive bo'lmagan shell. ~/.bashrc'da [[ $- == *i* ]] && return bo'lsa, sozlamalar yuklanmaydi.

Test qilish:

bash

* * * * * env > /tmp/cron-env.txt

Bir daqiqa kuting, keyin cat /tmp/cron-env.txt — cron muhitini ko'rasiz.

4.5. Logging va debugging

Default'da cron output mail orqali foydalanuvchiga yuboriladi. Agar mail sozlanmagan bo'lsa — yo'qoladi.

Yaxshi yo'l — har doim faylga yo'naltirish

cron

# Stdout va stderr ikkalasini bir faylga
0 2 * * * /opt/backup.sh >> /var/log/backup.log 2>&1

# Stdout va stderr alohida
0 2 * * * /opt/backup.sh > /var/log/backup.out 2>> /var/log/backup.err

# Hammasini yo'q qilish (umuman istamasangiz)
0 2 * * * /opt/silent.sh > /dev/null 2>&1

MAILTO o'chirish

Mail tashvishidan qutilish uchun crontab boshida:

cron

MAILTO=""

0 2 * * * /opt/backup.sh >> /var/log/backup.log 2>&1

Yoki aniq emailga:

cron

MAILTO="admin@example.com"

Tizim cron loglari

bash

# Ubuntu / Debian
tail -f /var/log/syslog | grep CRON

# RHEL / CentOS
tail -f /var/log/cron

# macOS
log show --predicate 'process == "cron"' --last 1h

Skript debug rejimi

bash

#!/usr/bin/env bash
set -euo pipefail

# Cron'da ishlasa, log'ga yozish
exec >> /var/log/myscript.log 2>&1
echo "===== $(date) =====" 

# ... asosiy ish ...

exec >> file 2>&1 — skriptning butun keyingi chiqishini faylga yo'naltiradi.

4.6. `at` — bir martalik kechiktirilgan vazifa

cron — takroriy. at — bitta marta kelajakdagi vaqtda bajarish.

bash

# Bugun 18:00 da
echo "/opt/notify.sh" | at 18:00

# Ertaga
echo "/opt/task.sh" | at 09:00 tomorrow

# 1 soatdan keyin
echo "/opt/reminder.sh" | at now + 1 hour

# Aniq sana
echo "/opt/event.sh" | at 14:30 2026-06-01

# Interaktiv (ko'p qator)
at 22:00
> notify-send "Vaqt boldi"
> /opt/cleanup.sh
> Ctrl+D

Boshqaruv

bash

atq           # kutilayotgan vazifalar
# 5    Sat May 17 18:00:00 2026 a ali

atrm 5        # bekor qilish

at -c 5       # ichidagi buyruqlarni ko'rish

Cron vs at — qachon qaysi

Cron — takroriy: backup, monitoring, cleanup
at — bir martalik: "ertaga ertalab serverni qayta yuklash"

4.7. `systemd` timers — zamonaviy muqobil

Modern Linux distributivlarida systemd mavjud — cron'dan ko'p afzalliklarga ega.

Tuzilish — `.service` + `.timer`

/etc/systemd/system/backup.service:

ini

[Unit]
Description=Nightly backup

[Service]
Type=oneshot
ExecStart=/opt/backup.sh
StandardOutput=journal
StandardError=journal

/etc/systemd/system/backup.timer:

ini

[Unit]
Description=Nightly backup timer
Requires=backup.service

[Timer]
OnCalendar=daily        # = soat 00:00
OnCalendar=*-*-* 02:00:00  # aniq 02:00
Persistent=true         # missed run'ni yetib olish
RandomizedDelaySec=30m  # 0-30 daqiqa tasodifiy kechiktirish

[Install]
WantedBy=timers.target

Yoqish va boshqarish

bash

# Reload (yangi fayl qo'shgandan keyin)
sudo systemctl daemon-reload

# Yoqish va boshlash
sudo systemctl enable --now backup.timer

# Status
systemctl status backup.timer
systemctl list-timers --all

# Loglar
journalctl -u backup.service       # service log
journalctl -u backup.service --since "1 hour ago"

# Manual ishga tushirish (test)
sudo systemctl start backup.service

`OnCalendar=` syntaxisi

ini

OnCalendar=hourly                       # har soat
OnCalendar=daily                        # har kun 00:00
OnCalendar=weekly                       # har yakshanba
OnCalendar=monthly                      # har oyning 1-kuni
OnCalendar=Mon..Fri 09:00               # ish kuni 9:00
OnCalendar=*-*-* 02:00:00               # har kun 02:00
OnCalendar=*:0/15                       # har 15 daqiqada
OnCalendar=Sat,Sun 04:00                # dam olishlarda

systemd-analyze calendar

bash

systemd-analyze calendar "Mon..Fri 09:00"
# Original form: Mon..Fri 09:00
# Normalized form: Mon..Fri *-*-* 09:00:00
# Next elapse: Mon 2026-05-19 09:00:00 +05

Buyurtma'ngiz to'g'riligini avval tekshiring.

4.8. `cron` vs `systemd` timers — qiyosiy

Xususiyat	`cron`	`systemd` timer
Yosh	1975	2010
Universal Unix	✅	❌ (faqat systemd-li Linux)
macOS / *BSD	✅	❌
Logging integratsiya	qo'lda	✅ journalctl
Missed run yetib olish	❌	✅ `Persistent=true`
Sandboxing (security)	❌	✅ to'liq
Resource limits (`MemoryMax`)	❌	✅
Dependency'lar (boshqa service)	❌	✅ `Requires=`
Sodda holatlar	✅	overkill
Kompleks workflow	qiyin	✅ tabiiy

Qoida

Bitta server, sodda vazifa → cron
Production xizmatlar → systemd timers
macOS → cron (yoki launchd)

macOS — launchd

macOS'da cron rasmiy deprecated (lekin hali ishlaydi). Tavsiya etilgan vosita — launchd (.plist fayllar ~/Library/LaunchAgents/).

Sodda holatlar uchun cron ishlatish mumkin. Lekin macOS'da cron ba'zan Full Disk Access ruxsatisiz ishlamaydi — System Preferences orqali berishingiz kerak bo'lishi mumkin.

4.9. `flock` — bir nusxa kafolati

Eng klassik cron muammo: skript 1 daqiqada bajarilishi kerak, lekin 2 daqiqa ishlamoqda. Keyingi tick'da yana ishga tushadi — ikki nusxa parallel. Disk yoki database ustida poyga.

Yechim: flock bilan lock fayl.

cron

* * * * * flock -n /tmp/myjob.lock /opt/myjob.sh

flock -n — lock olib bo'lmasa, darhol chiqadi (xato bilan). Ikkinchi instance ishga tushmaydi.

Skript ichida

bash

#!/usr/bin/env bash
exec 200>/var/run/myjob.lock
flock -n 200 || { echo "Allaqachon ishlamoqda"; exit 1; }

# ... asosiy ish ...

`flock` flag'lar

Flag	Mazmuni
`-n`	Lock olib bo'lmasa darhol chiqish
`-w <sec>`	N soniya kutib, keyin xato qaytarish
`-x`	Exclusive lock (default)
`-s`	Shared lock
`-u`	Unlock (qo'lda)

cron

# 30s kutib, keyin xato bersa, log'ga yozib chiqarish
* * * * * flock -w 30 /tmp/myjob.lock /opt/myjob.sh >> /var/log/myjob.log 2>&1

4.10. Real misol — Production-grade nightly backup

bash

#!/usr/bin/env bash
#
# nightly-backup.sh — production backup with notifications
#
# crontab entry:
#   0 2 * * * flock -n /tmp/backup.lock /opt/bin/nightly-backup.sh
#

set -euo pipefail
IFS=$'\n\t'

# === Konfiguratsiya ===
readonly SCRIPT_NAME="$(basename "$0")"
readonly LOG_FILE="/var/log/backup.log"
readonly SLACK_WEBHOOK="${SLACK_WEBHOOK:-}"
readonly HEALTHCHECK_URL="${HEALTHCHECK_URL:-}"

readonly BACKUP_DIR="/var/backups"
readonly SOURCE_DIRS=("/var/www" "/etc")
readonly KEEP_DAYS=14

# === Logging ===
exec >> "$LOG_FILE" 2>&1
echo ""
echo "===== $(date '+%Y-%m-%d %H:%M:%S') ====="

log() { printf '[%s] %s\n' "$(date '+%H:%M:%S')" "$*"; }

# === Notification ===
notify_slack() {
    [[ -z "$SLACK_WEBHOOK" ]] && return 0
    local msg="$1"
    curl -fsS -X POST -H 'Content-Type: application/json' \
        -d "{\"text\":\"$msg\"}" \
        "$SLACK_WEBHOOK" > /dev/null
}

# === Cleanup va xato handling ===
cleanup() {
    local rc=$?
    if [[ $rc -ne 0 ]]; then
        log "❌ Backup xato bilan tugadi (exit=$rc)"
        notify_slack ":x: Backup failed on $(hostname) (exit=$rc, see $LOG_FILE)"
    fi
}
trap cleanup EXIT

# === Asosiy ish ===
log "📦 Backup boshlandi"
mkdir -p "$BACKUP_DIR"

archive="$BACKUP_DIR/backup_$(date +%Y%m%d_%H%M%S).tar.gz"
log "📁 Arxiv: $archive"

if ! tar -czf "$archive" "${SOURCE_DIRS[@]}" 2>&1; then
    log "❌ tar yiqildi"
    exit 1
fi

size=$(du -sh "$archive" | cut -f1)
log "✅ Arxiv tayyor: $size"

# === Eski backup'larni tozalash ===
log "🧹 ${KEEP_DAYS} kundan eski'larni o'chirish..."
find "$BACKUP_DIR" -name "backup_*.tar.gz" -mtime "+$KEEP_DAYS" -delete

# === Healthcheck ping ===
if [[ -n "$HEALTHCHECK_URL" ]]; then
    curl -fsS --max-time 10 "$HEALTHCHECK_URL" > /dev/null \
        && log "💚 Healthcheck ping yuborildi"
fi

# === Success notification ===
notify_slack ":white_check_mark: Backup OK on $(hostname) — size: $size"
log "🎉 Yakunlandi"

Crontab entry

cron

SHELL=/bin/bash
PATH=/usr/local/bin:/usr/bin:/bin
MAILTO=""
SLACK_WEBHOOK=https://hooks.slack.com/services/...
HEALTHCHECK_URL=https://hc-ping.com/uuid-here

# Har kun 02:00 — lock bilan, single instance
0 2 * * * flock -n /tmp/backup.lock /opt/bin/nightly-backup.sh

Bu skript nima qiladi?

Xususiyat	Qaerda
Lock bilan single instance	`crontab`'da `flock -n`
Markaziy log fayli	`exec >> "$LOG_FILE" 2>&1`
Slack notification (success+fail)	`notify_slack`
Healthcheck.io ping	`curl HEALTHCHECK_URL`
Eski backup'larni avto-tozalash	`find ... -mtime +N -delete`
Trap orqali xato handle	`trap cleanup EXIT`
Production-grade error reporting	exit code → Slack alert

4.11. Tez-tez uchraydigan xatolar

Klassik tuzoqlar

PATH muammosi. Skript terminalda ishlaydi, cron'da yo'q. Yechim: to'liq yo'l yoki PATH=... crontab boshida.
Output yo'qoladi. Default'da cron output mailga ketadi. Yechim: >> file 2>&1 har doim.
MAILTO sozlanmagan, har daqiqa mail spam.MAILTO="" crontab boshida.
Cron'da ~ ishlamaydi.~ interactive shell uchun. Cron'da $HOME yoki to'liq yo'l ishlating.
crontab -r bilan adashish.-r = remove (hammasini). -e = edit. Tasodifan o'chirsangiz — yo'qotdingiz.
Time zone — UTC vs local. Server odatda UTC'da. Yangi server'da timedatectl status bilan tekshiring.
% belgisi cron'da maxsus. Cron qatorida % — yangi qator. Aniq belgi kerak bo'lsa, escape qiling: \%. Yaxshiroq — date +"%F" ni alohida skriptga o'tkazing.
Single instance kafolati yo'q.flock ishlatmagan bo'lsangiz — uzun ish 2 marta parallel ishlashi mumkin.
macOS'da cron Full Disk Access. System Preferences → Security & Privacy → Full Disk Access — cron qo'shing.
Cron faylida xato yangilanish tushunmaslik.crontab -e orqali save qilganda — darhol amal qiladi. Lekin SIGTERM yuborilmaydi: ishlovchi vazifa eski sintaksisni ishlatadi.

4.12. Mashqlar

🧪 Bashlings — interaktiv mashqlar

Bu bobning 7 ta mashqi bashlings CLI orqali avto-tekshiruv bilan. Hammasi cron daemon talab qilmaydi — sintaksis va parsing bilan ishlash:

bash

bashlings watch              # birinchi pending mashqdan boshlash
bashlings run cron1          # bitta mashqni tekshirish
bashlings hint cron1         # bosqichli maslahat

Manba: exercises/14_cron/

Quyidagi qo'shimcha kontseptual mashqlarni ham sinab ko'ring:

Cron syntax parser — quyidagi cron qatorlarini "har soat 30-daqiqasi" yoki "ish kuni 9-17 har 30 daqiqa" deb tushuntirish bo'yicha quiz:
- 30 * * * *
- */30 9-17 * * 1-5
- 0 0 1 * *
Logging wrap — quyidagi cron qatorni log + MAILTO bilan to'g'ri ko'rinishga keltiring:
cron
```
* * * * * mybackup.sh
```
1
flock lock — myjob.sh skripti uchun cron qatorida flock -n qo'shing va lock fayl /tmp/myjob.lock bo'lsin.
at reminder — 30 daqiqadan keyin "vaqti" deb chiqaruvchi at job yarating va atq orqali tekshiring.
Systemd timer — har 15 daqiqada ping qiluvchi myping.service va myping.timer faylini yozing.

4.13. Xulosa

Tushuncha	Asosiy nuqta
`crontab -e`	Tahrirlash
`crontab -l`	Joriy ro'yxat
`crontab -r`	⚠ HAMMASINI o'chirish
5 maydon	`daqiqa soat kun oy hafta-kuni`
`*/5`	Har 5 (step)
`@daily`, `@hourly`	Maxsus stringlar
`0 2 * * *`	Har kun 02:00
`>> log 2>&1`	Output har doim faylga
`MAILTO=""`	Mail spam'ni o'chirish
`PATH=...`	Cron'da o'rnatish majburiy
`flock -n /tmp/x.lock`	Single instance kafolati
`at 18:00`	Bir martalik kechiktirish
`OnCalendar=daily`	`systemd` timer ekvivalenti
`journalctl -u <service>`	`systemd` log'lar

5 ta asosiy g'oya

PATH cron'da minimal — to'liq yo'l yoki crontab boshida PATH=....
>> file 2>&1 har doim — aks holda output yo'qoladi.
flock -n — har production cron qatorida.
crontab.guru — murakkab syntax'ni online tekshiring.
systemd timer — Linux'da production uchun afzal (logging + sandboxing + missed-run catch-up).

🎉 Endi siz vazifalarni avtomatlashtira olasiz. Keyingi bobda — Docker orqali konteynerlar bilan ishlash.

Keyingi sahifa: 5. Docker bilan integratsiya →

4. Cron va vazifalarni rejalashtirish ​

4.1. Nima uchun rejalashtirish kerak? ​

4.2. cron asoslari ​

Asosiy buyruqlar ​

Joylashuvlar ​

4.3. Cron syntax — 5 ta maydon ​

Maxsus belgilar ​

Real misollar ​

Maxsus stringlar — @ ​

4.4. Cron environment va PATH muammosi ​

Cron PATH default ​

Yechim — 3 yo'l ​

4.5. Logging va debugging ​

Yaxshi yo'l — har doim faylga yo'naltirish ​

Tizim cron loglari ​

Skript debug rejimi ​

4.6. at — bir martalik kechiktirilgan vazifa ​

Boshqaruv ​

4.7. systemd timers — zamonaviy muqobil ​

Tuzilish — .service + .timer ​

Yoqish va boshqarish ​

OnCalendar= syntaxisi ​

4.8. cron vs systemd timers — qiyosiy ​

4.9. flock — bir nusxa kafolati ​

Skript ichida ​

flock flag'lar ​

4.10. Real misol — Production-grade nightly backup ​

Crontab entry ​

Bu skript nima qiladi? ​

4.11. Tez-tez uchraydigan xatolar ​

4.12. Mashqlar ​

4.13. Xulosa ​

5 ta asosiy g'oya ​

4. Cron va vazifalarni rejalashtirish

4.1. Nima uchun rejalashtirish kerak?

4.2. `cron` asoslari

Asosiy buyruqlar

Joylashuvlar

4.3. Cron syntax — 5 ta maydon

Maxsus belgilar

Real misollar

Maxsus stringlar — `@`

4.4. Cron environment va PATH muammosi

Cron PATH default

Yechim — 3 yo'l

4.5. Logging va debugging

Yaxshi yo'l — har doim faylga yo'naltirish

Tizim cron loglari

Skript debug rejimi

4.6. `at` — bir martalik kechiktirilgan vazifa

Boshqaruv

4.7. `systemd` timers — zamonaviy muqobil

Tuzilish — `.service` + `.timer`

Yoqish va boshqarish

`OnCalendar=` syntaxisi

4.8. `cron` vs `systemd` timers — qiyosiy

4.9. `flock` — bir nusxa kafolati

Skript ichida

`flock` flag'lar

4.10. Real misol — Production-grade nightly backup

Crontab entry

Bu skript nima qiladi?

4.11. Tez-tez uchraydigan xatolar

4.12. Mashqlar

4.13. Xulosa

5 ta asosiy g'oya