topic Re: Crontab not accepting changes in Operating System - Linux

Crontab not accepting changes

Idris Lirio — Thu, 13 Nov 2008 14:20:14 GMT

I have a problem with linux 7.3 crontab -e not writting the changes to the crontab file. Once crontab is opened for root it generates a file in the /tmp directory which is updated when I make changes and :w!, but after I exit with any other option wq, w, etc the tmp file disappears and the changes are not written to cron. There is also a message saying crontab: no changes made to crontab. any help with this is greatly appreciated.

Re: Crontab not accepting changes

Fredrik.eriksson — Thu, 13 Nov 2008 15:25:34 GMT

There could be a permission error?
I'm not sure where the "crontab -e" file is supposed to be stored.
But you could just aswell use /etc/crontab or a local crontab file which you can execute by running:
# crontab /path/to/local/crontab.file

Hope this helps you :)
Best regards
Fredrik Eriksson

Re: Crontab not accepting changes

Ivan Ferreira — Thu, 13 Nov 2008 17:51:41 GMT

Try removing and reinstalling your cron:

crontab -l > cron.root
crontab -r
crontab cron.root

Then try to edit again. This is to ensure that permissions for the cron file are correct.

Also, ensure that the crontab command has the SUID and SGID bit enabled:

# ls -la $(which crontab)
-rwsr-sr-x 1 root root 311288 mar 14 2007 /usr/bin/crontab

Re: Crontab not accepting changes

Idris Lirio — Thu, 13 Nov 2008 18:28:30 GMT

Ivan

I just tried this and still have the smae issue.

/var/spool/cron/root
-rw------- 1 root root 3.2k Nov 13 12:17 root

-rwsr-xr-x 1 root root 21080 Apr 14 2002 /usr/bin/crontab

The funny thing is I can edit the /var/spool file and crontab -e shows the changes, but a straight edit using crontab -e does not even when :w! is used and states cron was updated, but I suspect the update only refers to the /tmp file and not the actual cron file which is never updated on exit

Re: Crontab not accepting changes

Ivan Ferreira — Thu, 13 Nov 2008 18:32:51 GMT

Sometimes, when you have a syntax error in your cron file, for example, a missing value, the changes are not saved.

Â¿Can you upload a txt file with all your procedure?

Re: Crontab not accepting changes

skt_skt — Thu, 13 Nov 2008 19:48:38 GMT

check if your / fs is RW mode; You may not have /tmp as seprate file system now. give a try..

Re: Crontab not accepting changes

Idris Lirio — Thu, 13 Nov 2008 20:29:28 GMT

The file contains the entire crontab for root

Re: Crontab not accepting changes

Johnson Punniyalingam — Fri, 14 Nov 2008 03:30:44 GMT

#----------------------
# Monitor load avg on noble boxes
#----------------------
*/5 * * * * /root/monitor/loadavg.pl
#----------------------

above entry in your crontab looks to me wrong.

A crontab file has five fields for specifying day , date and time followed by the command to be run at that interval.

* * * * * command to be executed
- - - - -
| | | | |
| | | | +----- day of week (0 - 6) (Sunday=0)
| | | +------- month (1 - 12)
| | +--------- day of month (1 - 31)
| +----------- hour (0 - 23)
+------------- min (0 - 59)

Thanks,
Johnson

Re: Crontab not accepting changes

Dennis Handly — Fri, 14 Nov 2008 12:58:03 GMT

>Johnson: */5 * * * * /root/monitor/loadavg.pl
>above entry in your crontab looks to me wrong.

You might want to explain what you think is wrong? That "*/5" syntax seems to be linux for every 5 minutes. (Not valid for HP-UX though.)

Re: Crontab not accepting changes

Idris Lirio — Fri, 14 Nov 2008 15:42:14 GMT

I agree the */5 is a valid entry and we use it on our other 7.3 boxes which happen to be red hat. Sorry for not mentioing that earlier

Re: Crontab not accepting changes

Idris Lirio — Fri, 12 Dec 2008 17:43:55 GMT

I have found a possible cause for this but have not yet found a fix. The problem is with VIM and the way it handles tmp files I ran a stat and posted the results below. The way the stat should look. The Inodes should be the same after the w: and the modify and change times should be different than the access time.

Just After the file was opened:
File: "/tmp/crontab.6550"
Size: 2463 Blocks: 8 IO Block: -4611708214818369536 Regular File
Device: 803h/2051d Inode: 24 Links: 1
Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root)
Access: Fri Dec 12 10:48:18 2008
Modify: Fri Dec 12 10:48:18 2008
Change: Fri Dec 12 10:48:18 2008

After edit and :w to tmp file:
File: "/tmp/crontab.6550"
Size: 2478 Blocks: 8 IO Block: -4611721408957902848 Regular File
Device: 803h/2051d Inode: 24 Links: 1
Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root)
Access: Fri Dec 12 10:48:18 2008
Modify: Fri Dec 12 10:48:43 2008
Change: Fri Dec 12 10:48:43 2008

The problem I am having with the VIM editor.
Vim is creating a new tmp file with every write or save
Which causes the access, modify, and change times to be the same

File: "/tmp/crontab.18352"
Size: 3079 Blocks: 8 IO Block: -4611692890375057408 Regular File
Device: 805h/2053d Inode: 7209236 Links: 1
Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root)
Access: Fri Dec 12 10:19:28 2008
Modify: Fri Dec 12 10:19:28 2008
Change: Fri Dec 12 10:19:28 2008

After the w: on the tmp file:
File: "/tmp/crontab.18352"
Size: 3094 Blocks: 8 IO Block: -4611692890375057408 Regular File
Device: 805h/2053d Inode: 7209239 Links: 1
Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root)
Access: Fri Dec 12 10:19:56 2008
Modify: Fri Dec 12 10:19:56 2008
Change: Fri Dec 12 10:19:56 2008

If anyone has or knows of a way to correct this please advise

Re: Crontab not accepting changes

Dennis Handly — Sat, 13 Dec 2008 07:41:16 GMT

>The problem is with VIM and the way it handles tmp files

Why do you think this has anything to do with crontab?

>Vim is creating a new tmp file with every write or save, which causes the access, modify, and change times to be the same

What's wrong with that?

Re: Crontab not accepting changes

Idris Lirio — Mon, 15 Dec 2008 15:08:52 GMT

When using crontab -e if the change time is not different from the access time then the temp file is not written back to the original crontab file. This is shown in my previous posting of the stat that I ran on a working server compared to the non working. What I am looking for is a way to get vim to not create a new temp file every time a w or wq is initiated.

Re: Crontab not accepting changes

Dennis Handly — Tue, 16 Dec 2008 12:46:45 GMT

>When using crontab -e if the change time is not different from the access time then the temp file is not written back to the original crontab file.

This doesn't make sense. It should compare the modification time with the previous modification time, when it wrote it. But I suppose it doesn't like the fact that the inode has changed?

>This is shown in my previous posting of the stat that I ran on a working server compared to the non working.

That's a compelling argument.

>What I am looking for is a way to get vim to not create a new temp file every time a w or wq is initiated.

I'm not sure why it would do that? In the meantime, could you do the following:
:w
:touch %
:q

That way your modification time should be different from the inode change time.

Re: Crontab not accepting changes

Idris Lirio — Tue, 16 Dec 2008 14:11:17 GMT

The cause of the problem has been located. My /tmp directory is a symlink to another partition with more space which apparently due to the way vim handles files causes crontab -e to not work properly. /tmp must be an actual directory and not a symlink I have tested this and the problem of not saving the crontab went away when /tmp was an actual directory.

Thanks for all your help guys and the link below is where I found the answer to the problem.

http://bugs.gentoo.org/32938

Re: Crontab not accepting changes

Idris Lirio — Mon, 22 Dec 2008 14:07:00 GMT

Solution listed in previous post