I have php script on "first" Linux server that publishes websites on "second" Linux server. websites are being published just fine, except permissions and ownership for files and folder getting changed and make websites crash. So, I found the bash script on "second" Linux Server that changes it. But I don't understand what triggers it. There is nothing in php code that would trigger. And I don't know how to find these daemon or zombie process that get trigger when certain event happens. can someone help how to find that?
A cronjob could have been set to trigger this bash script to run. You can view crons for the current user with the command crontab -l
If it is a cron, edit the crontab with crontab -e and delete/edit the line that is causing the bash script to run. Alternatively you can just usr crontab -r to remove all the crons for the user
Related
I have modified my rc.local script to run some python script at startup.
This python script seems to be started successfully.
As the script is running forever (intended) and I want to see what the script does, my question is:
Is there a way to access the shell that runs this script?
Yes, to see what is going on, I could log to some file, but what if that script needs to get input from the user via console?
Thanks for your help!
You will not be able to interact with the script run by rc.local. But you can see what it does by logging its output into dedicated files:
python myscript.py > /home/myhome/log/myscript.log 2> /home/myhome/log/myscript.err
where error messages go into a separate log file.
Note that your script will be executed by root, having permissions and ownership accordingly.
Here's a link to an earlier answer about this with a method to log all outputs of rc.local.
Now you can see in your log file, if the execution stops due to the script demanding input or indeed crashing, and then you can fix the script accordingly.
If you don't want to mess with rc.local for testing, you could also first run it through crontab on your or root's account (scheduled execution by user, see man crontab). This might be easier for debugging, and you can start it through rc.local once it works as you want.
I work on an installation script for an embedded system (over ssh).
To do that, I have a first bash script who manage the partition size. After that, this script configure the execution of a second bash scrit at reboot with crontab.
The second bash script download and compile many things and it could take few hours. During this, the system must not be stopped!
The user could unplug the power of the system, and the best way to prevent any trouble with this is to show the installation progression to the user.
The user have to reconnect itself manually after the first reboot.
How can I print something into the ssh session of the user with the script launch by crontab at reboot?
You can modifiy SSHD to display a banner by modifying the /etc/ssh/sshd_config and uncommenting the Banner parameter. You can have your cron job or whatever you want update the file that it uses for the banner. The downside to this is that this message is only updated when the sshd is started.
you can put your message into any of the startup script. For example putting this line
echo "message you want to print at startup"
into ~/.bashrc file will print "message you want to print at startup" at startup after reboot.
I can't seem to run cron jobs and I can't figure out why. I'm new to this so I might be making an amateur mistake.
First, I create a script and call it 'test.sh', putting it in the /usr/local/bin folder. The script contains:
#!/bin/bash
echo "This test works!"
Next, I create a file called 'randomtest' in the /etc/cron.d folder. The file contains:
00 09 * * * root /usr/local/bin/test.sh >> /var/log/test.log
I expect the cron job to run at 9:00 AM every day, but for some reason, it doesn't. I also don't get a log file as expected. I checked the permissions on the test.sh file and it's currently set to 755, which should work.
Is there something I'm doing wrong? Am I missing a crucial element? Do I need to add my 'randomtest' file to the crontab or something?
Reload the cron daemon by using /etc/init.d/crond reload.
(Even if it's already running!)
The problem is that you're messing around with the /etc/cron.d directory rather than using the crontab command.
Unless you definitely need a cron job to run as root, just add it to your own crontab using the crontab command. You can use crontab -e to edit it, but it's better to keep your own copy of your crontab (ideally under version control) and use the crontab filename version of the command to install it. This ensure that the cron daemon will be aware of the update, and that any syntax errors will be caught. It also means you don't need to run any commands as root; avoiding root commands unless they're actually necessary is always a good idea.
Note that system crontabs (those in /etc/crontab and under the /etc/cron.d directory -- though those locations are implementation details that you ideally shouldn't have to worry about) have a different syntax than user crontabs; each line has an extra field that specifies the account under which the commans is to be run.
If you need a command to run as root, you can either update a system crontab file (carefully!), or you can set up a user crontab for the root user, using the normal crontab command as you would for any user account.
I'm having a peculiar issue with a shell script that I have set to run every minute via crontab.
I use Pelican as a blog platform and wanted to semi-automate the way in which the site updates whenever there's a new post. To do this, I've created a script to look for a file called respawn in the same directory as the content (it syncs via Dropbox so I simply create the file there which syncs to the server).
The script is written so that if the file respawn exists then it rebuilds the blog and deletes it. If it's not, it exits instead.
Here's the script called publish.sh
#!/bin/bash
Respawn="/home/user/content/respawn"
if [ -f $Respawn ]
then
sudo /home/user/sb.sh;rm $Respawn
else
exit 0
fi
exit 0
Here's the crontab for the shell script
* * * * * /home/user/publish.sh
And finally, here's the contents of sb.sh
make html -C /var/www/site/
Now, if I run the script via SSH and respawn exists, it works perfectly. However, if I let the cron do it then it doesn't run the shell script but it still deletes the respawn file.
I have one other cron job that runs every 4 hours that simply runs sb.sh which works perfectly (in case I forget to publish something).
I've tried using the user's crontab as well as adding it to root instead and I've also added the user to the sudoers file so it can be run without password intervention. Neither seem to work. Am I missing something?
It must be sudo. cron can't input the password.
Check mail for the user running the cron to confirm. Something like sudo: no tty present.
Try changing sudo /home/user/sb.sh;rm $Respawn to
/home/user/sb.sh;rm $Respawn
sudo is not necessary to run your command in this context, since it'll be invoked as root anyway.
I'm struggling trying to debug a cron job which isn't working correctly. The cron job calls a shell script which should unrar a rar file - this works correctly when i run the script manually, but for some reason it's not working via cron. I am using the absolute file path and have verified that the path is correct. Has anyone got any ideas why this could be happening?
Well, you already said that you have used absolute paths, so the number one problem is dealt with.
Next to check are permissions. Which user is the cron job run as? Does it have all the permissions necessary?
Then, a little trick: if you have a shell script that fails and it's not run in a terminal I like to redirect the output of it to some files. Right at the start of the script, add:
exec &>/tmp/my.log
This will redirect STDOUT and STDERR to /tmp/my.log. Then it might also be a good idea to also add the line:
set -x
This will make bash print which command it's about to execute, and at what nesting level.
Happy debugging!
The first thing to check when cron jobs fail is to see if the full environment is available to the script you are trying to execute. In other words, you need to realize that a job executed via cron runs as a detached process meaning it is not associated with a login environment. Therefore whenever you try to debug a cron job that works when you execute manually, you need to be sure the same environment is available to the cronjob as is available to you when you execute it manually. This include any PATH settings, and other envvars that the script may depend on.
For me, the problem was a different shell interpreter in crontab.