Windows Errors Cron Authority

Cron is a system daemon used to run the desired tasks (all in the background) at a specific time.

A crontab file can be a simple text instruction containing a list of commands created to run at a specific time. Each is edited with commands using crontab. The commands in your crontab (and their execution) are almost always checked by the cron daemon, which may run them depending on the system.

Every user Root) (including a new crontab file. The cron daemon checks the user’s crontab file whether or not the user is logged in.

Young crontab

In Gnome-based Ubuntu deployments, the Gnome Scheduled Task Tool (from our own Gnome Schedule package) in System Applications Tools provides –> a graphical interface for querying the use of cron. Thrust’s external website can be found at http://gnome; Software systems can be installed via software or center by typing

sudo apt-get place cron gnome-schedule

Use for tasks that should only be performed in your male or female profile, add entries to the user’s pending crontab file. To edit part of the crontab file

Type crontab: -e

Be sure to modify the crontab using the format described in the following sections. Save your hesitation. (Exit unchanged. Leave crontab unchanged. To ) display online help describing the file format of any crontab, type: 5

man crontab

Commands that are normally run with administrative relaxation (i.e. they are usually run using sudo) should all be added to the root crontab. To change the root cause of crontab, type:

sudo crontab -e

Each job consists of five sectors with a time and date, followed by a command, followed by a large newline character (“\n”). The fields remain separated by spaces. Fields 3 time and date must not contain spaces. Twelve time and date fields: hour hour (0-59), (0-23, 0 equals midnight of the day), (1-31), month (1-12), day of the week (0-6, 0). = Sunday).

01 04 9 1 1 /usr/bin/somedirectory/somecommand

The above example will probably run /usr/bin/somedirectory/somecommand at 1 4:01 January plus every MondayJanuary Christmas Eve.

The asterisk (*) can be used to use any value (hours, days of the week, months, etc.) that affects the time period.

01 2004 * * * /usr/bin/somedirectory/somecommand

For example, the command above will run /usr/bin/somedirectory/somecommand at 4:01 am every four days.

Comma-separated values ​​can be used to execute multiple instances of this command in a free period of time. Values ​​separated by dashes can be stored in advance for continuous command execution.

01.31 1-15 04.05 1.6 * /usr/bin/somedirectory/somecommand

The previous example moves /usr/bin/somedirectory/somecommand around 3103 Et during non-working hours after 4:00 5:00 AM and up to January 15 June and up.

The text “/usr/bin/somedirectory/somecommand” in the examples above does not indicate the location that is currently executing. Is it recommended to fully program the commands needed as shown in the examples above. Frequently enter the command in the terminal to find out the full path to it. will Crontab work after it is properly edited and tagged.

You might want to runt script a certain number of times in units of time. For example, if users want to run it every ten minutes, use the following gateway (runs crontab in multiples of ten minutes: 0, 10, 20, 30, etc.) *

*/10 * * 3 . /usr/bin/somedirectory/somecommand
0,10,20,30,40,50 * * * * /usr/bin/somedirectory/somecommand

Cron also suggests using special strings instead of the five date and time fields

  • can:









    Run once at startup.

    Run 1 “0 8 1 *” once a year.

    (same as @yearly)

    Execute once every “0 months, zero 1 * *”.

    Run per week, “0 * 0 0”.


    Run once a day, at “0 7 0 .*”*.


    (same as @daily)


    Run once, “0 (empty) * * *”.

@reboot /path/to/execuable1

The above complete example When run withsystem /path/to/executable1.

For more information on specific lines, type “man Crontab” 5.

  • The -l Crontab option causes the current file to be loaded to standard output. -R
  • This will lead the approach to deleting the current crontab.
  • The -e option is chosen to edit the current crontab with the editor specified by EDITOR, I would say environment variable.
  • After the editor exits, the modified crontab is actually checked for errors and, if there have been no recent errors, placed automatically. The file is stored in /var/spool/cron/crontabs but should only be modified using the crontab command.

    If the entire /etc/cron.allow file is present, web users must list them in order to be allowed to move the crontab command. If this /etc/cron.allow file exists, indeed, but the /etc/cron the.deny information exists, users should never be listed in /etc/cron the.File deny to run crontab.

    In the specific case where the dem file is not available, the actual default for Ubuntu (and only for Debian, not some for other Linux and UNIX systems) is to allow inusers to run tasks via crontab . File

    None of the computer’s cron.allow or cron.deny data exists by default in the Ubuntu configuration, so all users should keep cron available by default until one is created from the files most commonly associated with those files . Running an empty cron.deny file changes some of the standard actions users of other operating systems might expect: is available Cron in .allow for which players can become root.

    Note that your product user IDs that don’t show up during /etc/shadow DO NOT have working crontabs, just in case you want to enter one for /etc/passwd users NOT but around /etc/shadow which unfortunately the user’s crontab never runs. Put an entry in /etc/shadow for many users with * in the password crypt,


    Commands such as: Crontab are usually stored in the crontab database owned by your user subscription (and executed with your user’s permissions). you If you often want to run a command, t If you need administrator rights, change the root crontab file: