Solved: errors in crontab file, can't install - Unix & Linux (RHEL/CentOS 7/8)

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errors in crontab file, can't install

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Scenario 1: When number of crontab field is more than expected

I have been trying to set crontab from User root by running crontab -e command. After setting up the required fields I tried to save the crontab file multiple times but every time I got below error and it was not allowing me to save the file.

[root@localhost ~]# crontab -e
no crontab for root - using an empty one
crontab: installing new crontab
"/tmp/crontab.gsQNhu":1: bad command
errors in crontab file, can't install.
Do you want to retry the same edit? y
crontab: installing new crontab
"/tmp/crontab.gsQNhu":1: bad command
errors in crontab file, can't install.
Do you want to retry the same edit? y

-e : Edits the current crontab using the editor specified by the VISUAL or EDITOR environment variables. More can be checked on crontab Man Page.

Below is what my crontab file looks like when i got the above error. If you see the below output carefully then you will see an extra star(*) field due to which above error was showing.

0 3 * * * * /home/centos/example.sh

To resolve this issue i have removed that extra star(*) mark and then saved the file again. Then i am able to see below output which shows that crontab is successfully saved.

crontab: installing new crontab

Scenario 2: If you forget to mention the Script in Crontab File

Another scenario could be when you forget to mention the Script in Crontab File like the one showing below. Sometimes you might forget to mention the Script file which needs to run as part of cron job and then try to save the file. In those cases also you will get the same "errors in crontab file, can't install" error.

0 2 * * *

To fix this error you need to edit the crontab file and mention the script file name that needs to be run as part of the cron job.

Scenario 3: You might get "errors in crontab file can't install bad minute"

I have also seen a scenario where sometimes we might add an extra line like the one mentioned below then if you try to save this crontab file you will get "errors in crontab file can't install bad minute" error. This is because crontab expects to have a minute value mentioned at the start of every line. In this example, we have used a script called backup.sh at the start of the Line hence it will throw bad minute error.

0 3 * * * /home/centos/example.sh
backup.sh

Scenario 4: You might get "errors in crontab file can't install bad day-of-week"

I have also seen a scenario where sometimes Linux professionals uses some value in week section which is not expected hence started getting "errors in crontab file can't install bad day-of-week" error when try to save the file. One of the such instance I have shown below where week section expecting a value between 0 and 6 but instead 9 is mentioned which results in "bad day of the week" error.

* 4 0 * 9 /home/centos/example.sh

Scenario 5: You might get "errors in crontab file can't install bad command"

There is another common mistake I have seen Linux Professionals or Beginners often doing is that they will some unexpected command or a command which is not set in $PATH which results into "errors in crontab file can't install bad command" error. One such instance I have shown here where jq command is not there in any of the Linux binary path hence it is not detecting this command. In these cases either you need to provide the complete path of the command or add the command path in $PATH so that system detects that command.

0/10 * * * * jq

Scenario 6: You might get "bad day-of-month errors in crontab file can't install"

Finally I have also seen Linux professionals or beginners doing a mistake assuming month section as days of month section and will use any value greater that 12 resulting in "bad day-of-month errors in crontab file can't install" error. Here you need to be very careful in understanding the difference between days of the month and month of the year. Month of the year accepts value between 1 to 12 whereas days of the month accepts values between 1 to 31.