cron job question (for checking kernel updates)

[Ranjan Maitra]

On Wed, 2 Oct 2013 09:26:32 -0700 Rick Stevens <ricks at alldigital.com>
wrote:

> On 10/02/2013 08:10 AM, Ranjan Maitra issued this missive:
> > Hi,
> >
> > I have a cron job running which yum updates all my machines once a day.
> > All of these work fine.
> >
> > I also have a cron job which checks for kernel updates every hour and
> > sends me a message if an updated kernel has been installed. Here is the
> > relevant script:
> >
> > --- begin file called check-kernel.sh in my scripts/yum directory---
> >
> > #!/bin/bash
> >
> > latestkernel=$(rpm -q kernel |tail -n1|sed -e 's/kernel-//')
> >
> > #echo "$latestkernel"
> >
> > if uname -a | grep -qv "$latestkernel"; then
> > notify-send "Kernel UPDATE on ${HOSTNAME}: Running Kernel is $(uname
> > -r) but lat est installed rpm is ${latestkernel}; REBOOT required"
> > fi;
> >
> >
> > --- end file called check-kernel.sh ---
> >
> > (A bit wordy, I know.)
> >
> > I have verified that this is executable and works from the commandline
> > without any errors.
> >
> > I have the following set up via crontab -e:
> >
> > 0,15,30,45 * * * * nice -n 19 $HOME/.xplanet/download_xplanet_cloudmap
> > 5 * * * * nice -n 19 $HOME/scripts/yum/check-kernel.sh
> >
> > The first line downloads cloudmaps for use with xplanet and works just
> > fine (or appears to) and has done so for aeons.
> >
> > However, nothing happens (or appears to) for the second line.
> >
> > What is wrong here?
> 
> The most common problem I've seen is that cron jobs typically have very
> limited paths and the executables you're running (notify-send, uname)
> may not be in the path the cronjob has. For giggles, do "echo $PATH" as
> the user the cronjob will run as. Then build a cron job that echos
> cron's concept of the path:
> 
> 	#!/bin/bash
> 	echo $PATH >/tmp/pathecho.txt
> 
> and have cron run that once as the same user. Look at the data in
> /tmp/pathecho.txt and I'll bet you'll find its far more restricted than
> that of an interactive shell. 

I tried this: here is what I got --

$ echo $PATH
/bin:/usr/bin:/usr/local/bin:/usr/local/sbin:/usr/sbin:/home/user/bin

$ cat /tmp/pathecho.txt 
/usr/bin:/bin

Clearly more restrictive as you suggest. 

However, what I do not understand is why this does not "work" though. I
do not understand because notify-send is in /usr/bin as well as in /bin:

$ which notify-send 
notify-send is /bin/notify-send
notify-send is /usr/bin/notify-send

Both appear to be in the path. So where is the problem? 

I will also try the suggestions in the references in Matthew Miller's
response now.

Many thanks,
Ranjan






> To fix it, put in a
> 
> 	PATH="data from the echo $PATH command"
> 
> right after the "#!/bin/bash" line in your cron job. Since most of
> your commands are in /bin, you could do:
> 
> 	PATH=$PATH:/bin
> 
> and that would probably suffice (just making sure /bin is in the cron's
> path).




-- 
Important Notice: This mailbox is ignored: e-mails are set to be
deleted on receipt. Please respond to the mailing list if appropriate.
For those needing to send personal or professional e-mail, please use
appropriate addresses.

____________________________________________________________
FREE 3D EARTH SCREENSAVER - Watch the Earth right on your desktop!
Check it out at http://www.inbox.com/earth