Gabatarwar
Akwai daemon a cikin Linux da ake kira cron wanda ake amfani dashi don gudanar da tafiyar matakai a lokaci na lokaci.
Hanyar da yake yi shi ne duba wasu manyan fayilolin a kan tsarinka don rubutun don yin gudu. Alal misali akwai babban fayil da aka kira /etc/cron.hourly, /etc/cron.daily, /etc/cron.weekly da /etc/cron.monthly. Akwai fayil ɗin da aka kira / sauransu / crontab.
Ta hanyar tsoho zaka iya sanya rubutun cikin fayiloli masu dacewa don samun su don gudanar da lokaci na lokaci.
Alal misali buɗe wata taga mai zurfi (ta latsa CTRL, ALT da T) kuma ku gudanar da umarni na gaba :
ls / sauransu / cron *
Za ku ga jerin shirye-shiryen ko rubutun da aka gudanar a kowane lokaci, kullum, mako-mako da kowane wata.
Matsalar tare da waɗannan manyan fayiloli shine cewa suna da ban mamaki. Alal misali kullum yana nufin cewa rubutun zai gudana sau ɗaya a rana amma ba ku da iko a kan lokacin da rubutun zai gudana a wannan rana.
Wancan shine inda crontab fayil ya shiga.
Ta hanyar gyara fayil ɗin crontab za ku iya samun rubutun ko shirin don gudu a daidai kwanan wata da lokacin da kuke son shi ya gudana. Misali mai yiwuwa kana so ka ajiye fayilolinka kowane dare a karfe 6 na yamma.
Izini
Dokar crontab na buƙatar mai amfani yana da izini don shirya fayil crontab. Akwai fayiloli guda biyu da aka yi amfani dashi don gudanar da izinin crontab:
- /etc/cron.allow
- /etc/cron.deny
Idan fayil /etc/cron.allow ya wanzu to sai mai amfani yana so ya gyara fayil crontab dole ne a cikin wannan fayil. Idan fayil cron.allow bai wanzu ba amma akwai fayil /etc/cron.deny sai mai amfani bai kasance a cikin wannan fayil ba.
Idan fayiloli biyu sun kasance to /etc/cron.allow ya rinjaye fayil /etc/cron.deny.
Idan babu fayil ya kasance to sai ya dogara da tsarin tsarin ko mai amfani zai iya shirya crontab.
Mai amfani zai iya gyara fayil din crontab. Kuna iya amfani da umurnin su don canzawa zuwa mai amfani ko umurnin sudo don gudanar da umurnin crontab.
Ana gyara Crontab File
Kowane mai amfani wanda ke da izini zai iya ƙirƙirar fayil ɗin crontab na kansu. Cron umarni yana kallon wanzuwar fayilolin crontab da yawa kuma yana gudanar da su duka.
Don bincika ko kuna da fayilolin crontab gudu akan umarni mai zuwa:
crontab -l
Idan ba ku da wani crontab fayil sakon "babu crontab don
Don ƙirƙirar ko shirya fayil din crontab yana gudana umarnin nan:
crontab -e
By tsoho idan babu wani zaɓaɓɓen tsoho wanda aka zaɓa sannan a tambayeka don zaɓar mai yin tsoho don amfani. Da kaina ina so in yi amfani da Nano kamar yadda ya dace a yi amfani da shi kuma yana gudana daga m.
Fayil da ke buɗe yana da bayanai mai yawa amma ɓangaren ɓangaren shine misalin kafin ƙarshen sashe na sharhi (kalmomi suna ƙaddamar da layin da aka fara da #).
# mh dom mon dow umurnin
0 5 * * 1 tar -zcf /var/backups/home.tgz / home /
Akwai guda shida na bayanai don dacewa a kowane layi na fayil na crontab:
- A minti na yini umarni ne don gudu (m)
- Sa'a ɗaya na rana umarni shine ya gudu (h)
- Ranar watan wata umarni shine don gudu (dom)
- A watan umarni shine don gudu (dan)
- Ranar mako ta umarni ne don gudu (dow)
- Umurnin
Ga kowane abu (sai dai don umurnin) zaka iya saka halayen haruffa. Dubi misalai na crontab:
30 18 * * * tar -zcf /var/backups/home.tgz / home /
Abin da umarnin da ke sama ya fada shine a minti 30, 18 hours da kowace rana, wata da rana na mako suna yin umarni don aikawa da rubutu sannan kuma za a shigar da adireshin gida zuwa ga / var / backups fayil.
Don samun umurni don gudu a minti 30 bayan kowane sa'a zan iya tafiyar da umurnin mai biyowa:
Dokokin * * * * *
Don samun umurni don gudu a kowane minti na 6 da yamma na iya tafiyar da wannan umurnin:
* 18 * * * umurnin
Don haka sai ku yi hankali game da kafa dokokinku na crontab.
Alal misali:
* * * 1 * umurnin
Umurnin da ke sama zai gudana kowane minti na kowane sa'a kowace rana kowane mako a Janairu. Ina shakka wannan shine abinda kake so.
Don yin umurni a karfe 5 na farko a ranar 1 ga watan Janairu za ku yi umarni zuwa ga fayil crontab:
0 5 1 1 * umurnin
Yadda za a Cire fayil din Crontab
Yawancin lokaci ba zaka so ka cire fayil crontab amma zaka iya cire wasu layuka daga fayil crontab.
Duk da haka idan kana so ka cire fayil ɗin crontab mai amfani da kake bin umarnin nan:
crontab -r
Hanyar da ta fi dacewa don yin wannan shine don gudanar da umurnin mai zuwa:
crontab -i
Wannan yana tambaya tambaya "kun tabbata?" kafin cire fayil ɗin crontab.