Cron service for windows

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Стандартный планировщик Windows штука мощная, но столкнулся с проблемой, которая не позволила мне легко им пользоваться в «домашнем» выпуске Windows. Пришлось установить в систему настоящий cron. Ни капли не пожалел!
Как к этому пришёл, и что из этого поучилось под катом.

Пользователь без прав

Всё началось с того, что я хотел запланировать задание. Нужно было каждую минуту выполнять простой cmd-скрипт, который подготавливал окружение и запускал некий скрипт на Python.
Так как машина, на которой выполняется задание не основная рабочая, то нужно было выполнять задание, даже когда пользователь не зашёл в систему. Для этого был выбран режим:

Картинка с сайта: habr.com

При сохранении задания планировщик предупредил, что для указанного пользователя нужно разрешить «Вход в качестве пакетного задания». Для этого предлагается изменить политику безопасности. Однако сделать это не удалось, так как в «домашней» версии Windows нет оснастки для управления политикой безопасности (буду благодарен за подсказку альтернативного решения).
От запутанного конфигурирования стало как-то совсем грустно и захотелось мне иметь такой же простой и понятный инструмент как cron…

Cronизация Windows

Установка cron на Windows оказалась вполне реализуемой затеей. Я не стал искать специальной версии cron для Windows (поделитесь, если кто знает), а обратился сразу к Cygwin. Кроме стандартного пакета, я выбрал:

Картинка с сайта: habr.com

С пакетом cron всё понятно. Пакет cygrunsrv позволяет запускать разные программы как службы. После установки Cygwin можно переходить к конфигурированию cron.

Конфигурирование службы сron в Windows

Теперь переходим к самому ответственному шагу. Запускаем «Cygwin Terminal» с правами администратора и набираем команду:

> cron-config
Cron is already installed as a service under account LocalSystem.
Do you want to install the cron daemon as a service? (yes/no) yes
Enter the value of CYGWIN for the daemon: [ ] ntsec
Do you want to start the cron daemon as a service now? (yes/no) yes

Про ntsec можно подробнее почитать здесь.

Готово. Можно давать задания. Если служба не пошла, попробуйте её стартануть вручную:

> net start cron

Теперь открываете crontab и записываете задания (по умолчанию vi):

> crontab.exe -e

Можно «залить» задание через echo:

> echo "*/5 * * * * /cygdrive/c/crons/task.bat" >> C:\cygwin\var\cron\tabs\[Username]

Теперь перегрузите компьютер и посмотрите, как замечательно выполняются задания без входа в систему.

Cron is the standard Unix/Linux scheduler enabling you to execute commands at recurring intervals. Windows offers its own alternative scheduler with the Windows Task Scheduler.

Although there is no drop-in cron available in vanilla Windows, there are a number of options in addition to Windows’ Task Scheduler to execute jobs on a recurring schedule with the installation of additional software and/or subsystems. Some of them may be more appropriate than others depending on the use case.

Let us review how to setup the Windows equivalent of cron with Scheduled Tasks. Then we will explore of some of the other options to have cron-like functionality in Windows. They are: Windows Subsystem for Linux and Cygwin, other Windows scheduling software, and two of the GUI-based server management software (Plesk and WHM cPanel),

How do I set up scheduled tasks on a Windows server?

Windows offers its standard Task Scheduler to execute commands and scripts on a recurring schedule. Creating scheduled tasks can be done calling “Schtasks.exe” directly from the command line or using the GUI. One can also use the Powershell cmdlet Register-ScheduledJob to create scheduled jobs that will be executed by the Windows Task Scheduler.

We will expand on running a PHP script an a recurring schedule using the command line although the instructions can be applied to run any arbitrary programs.

Note: Create a batch file (optional). There are a number of advantages to creating a batch file and adding the command and parameter to be executed in the file. For example: You don’t need to edit the scheduled task unless the schedule needs to be updated, which require administrative privileges depending. If you are using a batch file to schedule the task, you can just edit the batch file to reflect the new command line.

If you are using XAMP for PHP, a batch file could look something like:

@echo off
D:\xampp\php\php.exe -f D:\www\yoursite.com\iem\admin\cron\cron.php > NUL

In the admin\cron directory, there is a file called “cron.php”. This is the file that you reference to execute Interspire meta scheduler. You will need the full path to this file, for example: D:\www\yoursite.com\iem\admin\cron\cron.php. Note that this path may be different on your web server and needs to be adjusted accordingly.

Task Scheduler Command Line

Scheduling Tasks using the command line is a matter of invoking “schtasks.exe” with the appropriate parameters. In its simplest form, to create a scheduled task that would run every 5 minutes invoking the hypothetical batch file above could be done by issuing:

C:\Users\demouser>schtasks.exe /Create /SC minute /MO "5" /TN "Interspire Cron" /TR "D:\bin\cron.cmd

The details of the syntax are well documented and can be consulted for more complex scenarios.

Task Scheduler GUI

The Task Scheduler GUI can be invoked by using the built-in search and either typing “Task Scheduler”, pressing “command R” and typing “taskschd.msc”, or by navigating to /Start/Windows Administrative Tools/Task Scheduler.

The Microsoft Management Console will open in a new window.

You can click on Create Task… which will give you access to set all the parameter of a scheduled task. Or you can click on Create Basic Task… which will start a wizard that will guide you through the creation process.

If you started the wizard with the Create Basic Task… the first step of the wizard is to enter a name and description for the task:

Картинка с сайта: www.interspire.com

Enter them then click on Next. The next screen is going to ask about what will trigger the task. Let’s select daily for this scenario:

Картинка с сайта: www.interspire.com

Click on Next. The next screen will allow you to set the recurrence. Let’s set it at Recur every day:

Картинка с сайта: www.interspire.com

Click on Next. And now you can select which command or script you can execute. Let’s re-use the hypothetical batch file from above:

Картинка с сайта: www.interspire.com

The last step of the wizard will present a summary of the scheduled task you just created:

Картинка с сайта: www.interspire.com

Click on Finish.

Note that the wizard does not offer to run a task more than once a day and the Trigger properties would have to be amended to run a task more than once a day. Find the task in the Task Scheduled list, right-click and edit the task, go to the Triggers tab and click on Edit…. Let’s set this task to run every 5 minutes for example:

Картинка с сайта: www.interspire.com

Click on OK to save your changes.

Powershell Register-ScheduledJob

You can also create scheduled jobs using Powershell and the Register-ScheduledTask cmdlet. A typical format is to call the cmdlet and pass the Action, Trigger, and TaskName to be created. To create our quintessential example of running a batch file every 5 minutes, open Powershell and issue the following:

PS C:\Users\demouser> $jobname="Interspire Tasks Every 5mn"
PS C:\Users\demouser> $action=New-ScheduledTaskAction -Execute 'c:\bin\cron.bat'
PS C:\Users\demouser> $schedule=New-JobTrigger -Once -At (Get-Date).Date -RepeatIndefinitely -RepetitionInterval (New-TimeSpan -Minutes 5)
PS C:\Users\demouser> Register-ScheduledTask -TaskName $jobname -Action $action -Trigger $schedule

Some will notice the schedule uses “New-JobTrigger” and not “New-ScheduledTaskTrigger”. I could not find a recurring interface below daily execution for “New-ScheduledTaskTrigger”. It seems that “Register-ScheduledTask” will take a New-JobTrigger argument for its schedule.

Alternatives to the Task Scheduler

Depending on your needs or preferences, using the native Windows Task Scheduler may not be the ideal choice. Let’s explore next two options which essentially install a Unix look alike (I know the two approaches are very different and neither are actually Unix look-alike).

Windows Subsytem for Linux

Microsoft offers Windows Subsystem for Linux. WSL basically allows you to install a Linux distribution of choice on top of Windows. The subsystem is completely integrated within windows allowing for seamless use of Windows programs and Linux tools along side each other within the same environment. The corollary is that the Linux cron system now becomes available for use within Windows.

There are many guides on installing WSL and will instead focus on some caveats to use cron in WSL.

The three main caveats of using cron from WSL are:

• WSL does not start by default on boot
• The cron services does not start by default with WSL
• WSL needs a privileged password to start the cron service.

Shout out to Ian Paul for his wonderful article “How to Launch Cron Automatically in WSL on Windows 10 and 11“, which provides a step-by-step way address the caveats above.

Let’s tackle the last one by allowing all to start the cron service without a password using sudo.

Edit the sudoers file

sudo visudo

Towards the end of the file right before the “includes” if you have any, add the following entry:

%sudo ALL=NOPASSWD: /usr/sbin/service cron start

Save the sudoers file. Next, let’s add a scheduled task using the Windows Task Scheduler to ask WSL start the cron service at boot time:

You can use the wizard as oulined above or do it from a privileged command line:

C:\users\demouser> schtasks.exe /Create /SC ONSTART /TN "Start WSL Cron Service at Boot Time" /TR "wsl.exe sudo /usr/sbin/service cron start”

One final note would be select that the service “Runs whether user is logged in or not”. Now the WSL cron service will start at every boot and Unix style crontabs can be used.

Cygwin

Cywin takes a totally different approach. Paraphrasing cygwin.com, Cygwin is a large collection of GNU and other open source tools that provide functionality similar to Linux in Windows. One of these tools is crontab.

Again, we will assume that Cygwin is already installed by running setup-x86_64.exe as detailed on the Cygwin web site. Cron is not part of the default installation set of Cygwin and must be added if it was not added already.

Start a Cygwin Terminal as an Administrator. Then instrall cron as a service on cygwin:

cygrunsrv --install cron --path /usr/sbin/cron --args -n

Another shout out this time to David J Nice for https://www.davidjnice.com/cygwin_cron_service.html regarding in particular what arguments to pass to cron on startup.

Once this is done, you can use the usual GNU/Linux commands to manage cron such as crontab -e to edit your crontab. You can review our article “Setting Up Scheduled Sending Using Cron“ to get more details on the crontab file format.

Other Windows Scheduling Software

In addition to using the vanilla Task Scheduler or installing Linux tools alongside / on top Windows, there are also a number of Windows scheduling apps. Some are:

• Z-cron https://z-dbackup.de/en/z-cron-scheduler/
• Visual Cron https://www.visualcron.com

The internet also has a number of sites compiling lists of windows scheduling software

Web Control Panel

The last category we will mention are for servers that are managed via a web-based control panel such as Plesk. Although Plesk is mostly used to managed GNU/Linux servers, it can also be installed on Windows server as well.

Plesk calls their cron / scheduling “Scheduled Tasks”.

If you have multiple domains, select the domain you want to add a scheduled task for.
Navigate to the Scheduled Tasks/Add Task to schedule a new task.
Choose “Run a command” the the task type.
Enter the command you want schedule.
Select the frequency for recurring tasks or the specific date and time as appropriate.
If possible, click “Run Now” to verify the setup, then on “OK” to save the new schedule task.

Refer to the Plesk Documentation for more details.

Final Thoughts

Although Windows does not have a drop-in cron like system, it offers the Windows Task Scheduler which provides equivalent scheduling services. With a little bit of legwork, one can also have access to more cron-looking scheduling using Windows Services for Linux and Cygwin. Also, there are native Windows Task Scheduler alternatives, and lastly, it is possible to have access to a Windows server that is managed by a web based control panel.

The best approach to use will depend on your use case and personal preferences. Happy Windows scheduling.

Note: This tutorial is based on Windows 10, and there may be slight variations in using Task Scheduler on other Windows versions.

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Installing & Configuring the Cygwin Cron Service in Windows.

To set up cron on Cygwin, you’ll need to install two additional cygwin packages using the cygwin setup.exe:

• cron: Vixie’s Cron
• cygrunsrv: NT/W2K service initiator

Both programs are in the «Admin» category. Cron is the cron-daemon and Cygrunsrv is the program used to install & manage Cygwin programs as Windows services.

You’ll also need vi(m) installed if you haven’t already as it’s the default editor for the crontab command. (It is possible to use another editor such as nano provided you set it as your default editor in your bash profile.)

Once you have the packages installed you can install cron as a Windows Service using Cygrunsrv.

cygrunsrv —install cron —path /usr/sbin/cron —args -n

There are a lot of web posts that say you should use cygrunsrv -I cron -p /usr/sbin/cron -a -D (See Errors #1 & #2).

By default, cron will install as a service that uses the Local System account. If you test cron at this point — for Windows 2003 at least — the windows event log will show Windows Application Event Log: (CRON) error (can’t switch user context) — See error #3. This is because your test crontab is set up as the local administrator but the service is running as the ‘Local System’ account and does not have permission to create a token object.

To finish off the install, create a new user called cygrunsrv and use the Local Security Policy snap-in to allow that user to ‘Create a token object’, ‘Logon as a service’ & ‘Replace a process level token’ using the local group policy.

You will also need to add the user to the Local Administrators Group. I’ve added this as a note because I’m currently checking what permissions are really required. If it’s possible, it would be better to not have this account added to the Local Administrators Group.

Set the service to run as .\cygrunsrv, set the password and restart the cron service.

You can start and stop the cron service by using:

• Using the Windows Services Snap-in
• From a cmd window or run dialogue; ‘net start cron’ & ‘net stop cron’
• Or, since you are setting this up in Cygwin; ‘cygrunsrv —start cron’ & ‘cygrunsrv —start cron’

To test the service, set up a crontab as the local administrator and check that it runs. A good test is to open a cygwin bash shell and run

$crontab -e

This will open the crontab in vi(m). Add the following line:

* * * * * echo «Cron test at $(date +\%k:\%M)» >> /cygdrive/c/crontest.txt 2>&1

(A little tip here; if you use the date command in a cron job, you need to escape the % characters will a backslash otherwise it won’t work…)

If everything is running correctly this will generate a file called c:\crontest.log and add a new line every minute.

Common errors and their solutions.

#1 cygrunsrv: Error starting a service: QueryServiceStatus: Win32 error 1062: The service has not been started.

This error appears in the Cygwin shell windows when you try to start the service. It is accompanied by error #2 in /var/log/cron.log. The resolution is the same as error #2.

You may find that although it appears that the service didn’t start, it did start but just stopped again. When this happens you may find that you have a cron process running that will lead to error #4 the next time you try to start the service.

#2 cygwin cron «unknown option — D» appears in /var/log/cron.log

To fix this use -n instead of -D: ie cygrunsrv —install cron —path /usr/sbin/cron —args -n

From the Man Page

Cron should be started from /etc/rc or /etc/rc.local. It will return immediately, so you don’t need to start it with ‘&’. The -n option changes this default behavior causing it to run in the foreground. This can be useful when starting it out of init.

#3 Windows Application Event Log: (CRON) error (can’t switch user context)

This error appears in the Windows Application Event Log and occurs because the account running the service can’t switch user context. In other words, the cron service is running using one account — e.g. Local System — and can’t switch to run as the account to whom the crontab being run belongs to. This can be resolved by using an account especially created for the job of running the cron server — in this how-to that account is ‘cygrunsrv’.

#4 /usr/sbin/cron: can’t lock /var/run/cron.pid, otherpid may be nnnn: Resource temporarily unavailable

Cron is already running a process. When you are having issues setting up cron, you may find that although the service stopped, cron is left running as an orphan process in the background. Use ps -a to find the process and then use kill -9 to finish it off!

Appendices.

What the switches mean in the cygrunsrv command.

cygrunsrv —install cron —path /usr/sbin/cron —args -n

The switches are:

• —install (-I) Installs the service on Windows.
• —path (-p) Gives the full path to the executable as Cygwin sees it.
• —args (-a) Passes any arguments to the executable that you might need. You can add more than one by surrounding them in double quotes.

Cron Commands.

• ‘cygrunsrv —start cron’ from a Cygwin shell: Starts the Cron Service
• ‘net start cron’ from a Windows command prompt: Starts the Cron Service
• ‘cygrunsrv —stop cron’ from a Cygwin shell: Stops the Cron Service
• ‘net stop cron’ from a Windows command prompt: Stops the Cron Service
• crontab -e: Edit a crontab
• crontab -l: List a crontab

For additional information in /var/log/cron.log you can use debug flags by adding the switch ‘-x’

e.g. cygrunsrv —install cron —path /usr/sbin/cron —args «-n -x sch,proc,pars,load,misc»

• sch :be verbose when iterating through the scheduling algorithms
• proc :be verbose about the state of the process, including all of its offspring
• pars :be verbose about parsing individual crontab lines
• load :be verbose when loading crontab files
• misc :be verbose about miscellaneous one-off events
• bit :currently not used
• ext :make the other debug flags more verbose
• test :trace through the execution, but do not perform any actions

Local Security Policy.

When you add the user to the service, Windows will automatically enable that user to run as a service. You can put this back to the default setting in your Local Security Policy settings.

From the openssh.README.txt (in regards to cygrunsrv).

Useful Links.

• Using Windows security in Cygwin.
• cygrunsrv.README.
• Understanding and Configuring User Account Control in Windows Vista.