Tar error：通过Cron / PHP运行时存档中的意外EOF

Question

I have a PHP console script that is called via cron which itself among other things creates a tar file of a directory.

When calling the PHP script via cron the the tar file is not created correctly. The following error is given when viewing the tar file:

gzip: stdin: unexpected end of file
tar: Unexpected EOF in archive
tar: Error is not recoverable: exiting now

When calling the PHP script manually via console the tar file is created correctly. The cron log output shows no errors.

Here the tar call form the PHP script.

 exec("cd $this->backupTempFolderName/$id; tar -czf ../../$this->backupFolderName/$tarFileName $dbDumpFileName documents");

Dose anybody have an idea why the tar is created correctly when manually called and fails when called via cron?

Update : The error given while creating the tar file via cron is:

tar: ../../backup/20150819-060003.tar.gz: Wrote only 4096 of 10240 bytes
tar: Error is not recoverable: exiting now

Sometimes the error is:

tar: ../../backup/20150819-054002.tar.gz: Cannot write: Broken pipe
tar: Error is not recoverable: exiting now

As said before, the when executed via cron the tar file is created, but always 50% of the correct size (when manually executing the script):

-rw-r--r--  1 gtz gtz 1596099468 Aug 19 06:25 20150819-042330.tar.gz <- Manually called skript, working tar
-rw-r--r--  1 gtz gtz  858570752 Aug 19 07:21 20150819-052002.tar.gz <- Script called via cron, broken tar

Update 2

After doing some further research based on the input given here, might should add that the cron called script is running on a virtual private server - I suspect that some limitations may exist for cron jobs that are not documented by the hoster (only limit on minimum repetition time is given in the docs).

Answer 1

That error comes usually from lack of disk space.

I would do some more researching on this subject, by adding some logs before and after the tar execution.

Also check what user your configuration is using for the cron job you have running the backup. It can be some quota limit on that user as well, that doesn't happen when you run on the console outside cron.

Ask your provider for quota limits on the VPS for users and for processes... That is what rings the bell here.

Answer 2

I guess that you have a resource limitation As M. Ivanov has said, add this command in your PHP script:

shell_exec("php -info");

and check this parameter both when you execute your script from command line and from cron job

memory_limit => ???

You can also try to run your cron by enhancing the memory limit to 1600M

php -d memory_limit=1600M scriptCompressor.php

Hope that helps :)

Answer 3

cronjobs by themselves usually don't have limits. If you are using shared hosting they may have installed some enforcing scripts but I suspect they would also break your console backups.

If you are running cronjobs from some container, eg Drupal, they have special limits.

Also check bash limits with: ulimit -a

Report disk space before backup starts and afterwards just in case. It's usually quite small on VPS.

Answer 4

You may want to try creating the tarball directly from PHP to avoid the exec call. See this answer: https://stackoverflow.com/a/20062628/5260945 .

Also, looking at your cron entry, there is no leading slash on your example. I know this could just be a typo for the comment, but make sure you have an absolute path for the cd command. The default environment for a cron job is not the same as for your login shell.

Answer 5

I am sure its memory or execution time problem. Do one thing run the same script for directory which contains only single test file and check the output, if your script works in this scenario then 100% sure its memory problem.

try to tweak memory parameter and execute your script.

I hope this help you.

Thanks

Answer 6

Looking at the following error.

tar: ../../backup/20150819-054002.tar.gz: Cannot write: Broken pipe
tar: Error is not recoverable: exiting now

I see that as the exec function in the PHP script is not blocking or causing an error prematurely. So the PHP session that get's called during the Cron job exits before the command finishes. This is just a guess but you can try to send this to the background when you run it from Cron.

exec("cd $this->backupTempFolderName/$id; tar -czf ../../$this->backupFolderName/$tarFileName $dbDumpFileName documents &");

This command should be blocking so this is just a shot in the dark.

http://php.net/manual/en/function.exec.php

Answer 7

Error occurs when you trying to execute the php file and gives EOF error. It means somewhere in your php file you must check the code of your cron file it may happen that you forget to complete the brackets of the condition or class etc...

Good luck ['}

Answer 8

To write the errors to the log when executed via cron replace >/paht/to/application/app/logs/backup-output.log in the cron line by 2>&1 >/path/to/application/app/logs/backup-output.log Also check the path in the cron line .. maybe the change-dir is not working as you might think. Try printing getcwd() to a log or something, when running the php script from cron.

Edit: I wonder why this was voted not useful . The questioner mentioned that no errors are printed to the log when the cron executes the script. Thats not hard to imagine as > just redirects the STDOUT and not the STDERR (on which php errors would get printed) to the log. So adding 2>&1 might reveal some new informations.