I noticed that when I typed sudo crontab -e I dont see my cron command, but when I do only crontab -e there is my command.
Is there a difference between the 2? If there is, where should I put my cron command, should it be in sudo or without the sudo?
Thanks!
Is there a difference between the 2?
Yes, indeed they are different.
The difference is that with sudo crontab -e the commands are schedule with root user's credentials. So that the commands in the sudo's cron table are executed as root user.
But with crontab -e, the commands are scheduled with the regular user who is logged in.
Where should I put my cron command, should it be in sudo or without the sudo?
Well, the answer to this depends on the type of command you want to run.
If the command required sudo access then sudo crontab -e should be used.
Else if the cron command doesn't require any special permission then use crontab -e.
Example:
If the ethernet network interface eth0 should be disabled or enabled at specific time then you would use the command
ifconfig eth0 up or ifconfig eth0 down
As the above commands require special permission (sudo), these commands are supposed to added to sudo's cron tab
Any other command which require minimal permission or no permission like removing a file from tmp directory like $ rm /tmp/somefile use the regular user's crontab.
Main part of the problem is to take care of the user with whom you wanna make your things done. Otherwise it will not trigger your cron job. And do make sure that you write output of your command in any file. It will help you to debug the problem which most probably might relate to your relative paths.
That's what I faced difficulties in. You can move forward following the below step:
identify your username with which you wanna go. Use whoami command.
Turn to your selected user mode and type crontab -e.
And append line < cron-schedule your-command >> output_filename.cron 2>&1 >
That's it.
Thanks!
Related
When I execute swapoff -a && swapon -a that works like a charm and when I create a scriptfile swap.sh and I run that it works great too.
chmod 755 swap.sh
But when I make a crontab that should execute the script, than nothing happens.
crontab -e
0 2 * * * /scripts/swap.sh
Am I missing something here?
Since you confirmed the script is running as super user (sudo) and the file has permissions to execute the problem is other thing (cron in this case):
Try using the full path
/sbin/swapoff -a && /sbin/swapon -a
You have to use full absolute pathnames in crontab commands because when cron runs a script, it does not perform initial login activity (which is where the path(s) are set).
All credits go to: https://ubuntuforums.org/archive/index.php/t-1766875.html
I want to edit system cron tab (/etc/crontab). I read that crontab -e is the best way to edit crontab and you need not restart cron services if you edit this way. However I am not able to edit /etc/crontab using crontab -e (this command edits the crontab associated with the user, not system crontab). So is there any better way of editing /etc/crontab (other than using VI editor- which I am doing now). Do I need to restart cron services if I edit /etc/crontab using VI edior?
There are two ways of cronjobs, one is by editing /etc/crontab and sending a SIGHUP the cron daemon. The other way is to use crontab -e to edit
a crontab entry, which is done for the current user or the one mentioned with -u. The -u option can only be used by root. The crontabs
created this way can be found in the directory
/var/spool/cron/crontabs/
and are named after the user with which uid the jobs will be started. In this case you don't need to SIGHUP cron, a normal user can't do this anyway.
Note: The syntax is slightly different to /etc/crontab: You can't enter an other user name to execute the cronjob.
You could do something like this
echo "0 23 * * * yum -y update > /dev/null 2>&1" >> /var/spool/cron/root
Then verify with
crontab -l
I have to execute a process on a cluster of machines. Size of cluster is of order 100. So I cannot execute processes manually, I have to execute them by script(which uses ssh, currently I am using python-paramiko for this). Number of tcp sockets these processes open is more than 1024(default limit of linux.) So I need to change that using {ulimit -n 10000}. This makes the changes for that shell session only. And this command works only with root user. So my script is not able to do that.
I tried to execute this command
sudo su && ulimit -n 10000 && <commandToExecuteMyProcess>
But this didn't work. The commands after "sudo su" didn't execute at all. They execute only when I logout of the su session.
This article shows way to make the changes permanently. But when I open limits.conf, I didn't find anything there. It only has some commented notes.
Please suggest me some way to increase the limit permanently or change it by script for each session.
That's not how it works: sudo su just opens a new shell so you can introduce commands as root, and after you exit that shell it executes the rest of the line as normal user.
Second: your this is a special case because ulimit is not actually a program, but a bash shell built-in command, so it must be used within bash, that is why something like sudo ulimit -n 10000 won't work: sudo can't find that program because it doesn't exist.
So, the only alternative is a bit ugly but works:
sudo bash -c 'ulimit -n 10000 && <command>'
Everything inside '...' will execute in a bash session of the root user.
Note that you can replace && with ; in this case: that's because it is being executed as root and ulimit -n 10000 will always complete successfully.
I am trying to run a shell script on crontab on Ubuntu platform. I have tried googling and other links but nothing has helped so far.
This is my crontab:
*/2 * * * * sudo bash /data/html/mysite/site_cleanup.sh
This is the content of my sh file:
#!/bin/sh
# How many days retention do we want ?
DAYS=0
# geting present day
now=$(date +"%m_%d_%Y")
# Where is the base directory
BASEDIR=/data/html/mysite
#where is the backup directory
BKPDIR=/data/html/backup
# Where is the log file
LOGFILE=$BKPDIR/log/mysite.log
# add to tar
tar -cvzf $now.tar.gz $BASEDIR
mv $now.tar.gz $BKPDIR
# REMOVE OLD FILES
echo `date` Purge Started >> $LOGFILE
find $BASEDIR -mtime +$DAYS | xargs rm
echo `date` Purge Completed >> $LOGFILE
The same script runs from a terminal and gives the desired result.
Generic troubleshooting for noninteractive shell scripts
Put set -x; exec 2>/path/to/logfile at the top of your script to log all subsequent commands to a file as they're run. If this doesn't work, you'll know that your script isn't being run at all; if it does, you'll know where it fails and how.
If this is a personal crontab
If you're running crontab -e as a user (without sudo), then the crontab being modified is one for commands run with that user's permissions. Check that file permissions allow that user to modify the content in question (which, if these files are in a cgi-bin directory, may require being run by the same user as the web server).
If your intent is to have commands run as root, rather than as your own user, be sure you use sudo when editing the crontab to edit the system crontab instead (but please take care as to your script's correctness in this case -- carelessness such as missing quotes or lack of appropriate precautions in xargs usage can cause a script to delete the wrong files if malicious filenames are created):
sudo crontab -e ## to edit the system (root) crontab
...or, if you're cleaning up files owned by the apache user (for example; check which account is correct for your own operating system and web server):
sudo -u apache crontab -e ## to edit the apache user's crontab
Troubleshooting for a system crontab
Do not attempt to put a sudo command within the commands run by cron; with sudo's default configuration, it requires a TTY (a keyboard and screen) to be attached to a session in order to run. Thus, your crontab line should not contain sudo, but instead should look like the following:
*/2 * * * * bash /data/html/mysite/site_cleanup.sh
Your issue is likely coming from the sudo call from your user level cron. Unless you've gone through and edited the bashrc profile to allow that script to run without sudo it'll hang up every time.
So you can lookup how to run a script with no password by modifying the bashrc profile, remove the sudo call if you aren't doing something in your script that calls for Super User permissions, or as a last ditch, extremely bad idea you can call your script from root's cron by doing sudo crontab -e or sudo env EDITOR=nano crontab -e if you prefer nano as your editor.
try to add this line to the crontab of user root and without the sudo.
like this:
*/2 * * * * bash /data/html/mysite/site_cleanup.sh
Ok I'm about to pull my hair out. I have a perl script that just will not run in the crontab however I have a previously written perl script that runs just fine every day on the same box. I have checked all of the given solutions on this site and others around the web and nothing seems to make a difference. Here is my cron and the first part of my script
55 13 * * * su oracle; cd /u02/oraclebackup;./move_em_bkup.pl >> /u02/oraclebackup/move_em_backup.log > move_em_bkup.dbg 2>$1
It touches the .dbg file but does not put anything in there. There are no errors or anything that I can use to go by.
#!/usr/bin/perl
use Strict;
use Archive::Tar;
use Net::SCP qw/ scp /;
use Net::SCP::Expect;
use DateTime;
Can anybody help?
The command you're running is:
su oracle; cd /u02/oraclebackup; ...
su oracle normally launches an interactive shell under the oracle account (assuming you have permission to do so). I'm not sure what that would do in a non-interactive cron environment, but even assuming it works, the cd /u02/oraclebackup and following sub-commands will be executed after that shell terminates, i.e., under the account that owns the crontab. The su oracle will either block the rest of the command or do nothing.
You can use su -c command to run a command as a specified user. In you case, you'd want something like:
su -c oracle sh -c 'cd /u02/oraclebackup; ...'
Or change su to su - if you need the oracle account's login environment.
Better yet, drop the su and put the whole thing in the oracle account's crontab. You might still need to play some more tricks to get the environment right; cron jobs run with a limited set of environment variables by default.