Home » How do I completely silence a cronjob to /dev/null/?

How do I completely silence a cronjob to /dev/null/?


Make the line this:

* * * * *       root    /usr/local/sbin/mycommand.sh > /dev/null 2>&1

This will capture both STDOUT (1) and STDERR (2) and send them to /dev/null.


You can also disable the email by setting and then resetting the MAILTO="" which will disable the sending of any emails.


* * * * *       root    /usr/local/sbin/mycommand.sh > /dev/null 2>&1

 * * * * *      root    /usr/local/sbin/myothercommand.sh

Additional messaging

Often times you’ll get the following types of messages in /var/log/syslog:

Nov 11 08:17:01 manny CRON[28381]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)

These are simply notifications via cron that a directory of cronjobs was executed. This message has nothing to do directly with these jobs, instead it’s coming from the crond daemon directly. There isn’t really anything you can do about these, and I would encourage you to not disable these, since they’re likely the only window you have into the goings on of crond via the logs.

If they’re very annoying to you, you can always direct them to an alternative log file to get them out of your /var/log/syslog file, through the /etc/syslog.conf configuration file for syslog.

have a script which needs to be executed each minute. The problem is that cron is logging to /var/log/syslog each time it executes. I end up seeing repeated the message it was ececuted over and over in /var/log/syslog

Since nothing you do seems to stop this, it is worth asking: what exactly is this script and what exactly is the message you see in syslog?

If slm’s suggestion did not work, this is because something is logging to syslog directly — either cron, as seems to be implied in some of your comments, or else the process run by cron. Messages sent to syslog do not come from stdin or stderr, so 2>&1&> will not help.

There might be a way to configure the behavior of the application in question, except we don’t know what it is.

There certainly is a way to configure most contemporary syslog implementations (there are several) to filter messages very specifically. For example, if there is a unique tag used in the log message, you can target that. But again, since we don’t know anything about the particular message, or which syslogd you use, then there’s nothing specific that can be recommended.

My general point is that if you don’t want to redirect/filter messages because “this will redirect all the messages”, then you can refine the filtering technique. The server fault thread you linked to just mentions filtering by facility (*.cron) — but you can configure more specialized filters than that.

Debian and Ubuntu both have rsyslog available. On debian 5+ it is the default syslog, on ubuntu it is an option, so you’ll have to install it. To create a filter that targets some kind of specific content, place this near the top (i.e., before any other rules, but after the general configuration, module loading, etc) of /etc/rsyslog.conf. Best way to do this is not to edit the rsyslog.conf itself, but to create a file in /etc/rsyslog.conf.d/ directory, with name starting with two digits which are less than 50, ie /etc/rsyslog.conf.d/15-my-filter.conf. You can put there something like this:

:msg, contains, "/usr/bin/w3m -no-cookie" /dev/null

This will send the message to /dev/null (or a separate log if you prefer). However, the message will still be passed through the subsequent rules which send it to /var/log/syslog. To prevent that:

& stop

Immediately after that other line. This throws away anything which matched the preceding rule. Or, for single-line rules you can just add stop to the end of that rule line.

You have to restart rsyslogd after changing the configuration, (e.g. on systemd systems systemctl restart rsyslog):

kill -HUP $(cat /var/run/rsyslogd.pid)

HUP causes the daemon to restart itself.

Change /etc/default/cron

# Or, to log standard messages, plus jobs with exit status != 0:
# For quick reference, the currently available log levels are:
#   0   no logging (errors are logged regardless)
#   1   log start of jobs
#   2   log end of jobs
#   4   log jobs with exit status != 0
#   8   log the process identifier of child process (in all logs)

By default the EXTRA_OPTS line is ""

Related Solutions

Joining bash arguments into single string with spaces

[*] I believe that this does what you want. It will put all the arguments in one string, separated by spaces, with single quotes around all: str="'$*'" $* produces all the scripts arguments separated by the first character of $IFS which, by default, is a space....

AddTransient, AddScoped and AddSingleton Services Differences

TL;DR Transient objects are always different; a new instance is provided to every controller and every service. Scoped objects are the same within a request, but different across different requests. Singleton objects are the same for every object and every...

How to download package not install it with apt-get command?

Use --download-only: sudo apt-get install --download-only pppoe This will download pppoe and any dependencies you need, and place them in /var/cache/apt/archives. That way a subsequent apt-get install pppoe will be able to complete without any extra downloads....

What defines the maximum size for a command single argument?

Answers Definitely not a bug. The parameter which defines the maximum size for one argument is MAX_ARG_STRLEN. There is no documentation for this parameter other than the comments in binfmts.h: /* * These are the maximum length and maximum number of strings...

Bulk rename, change prefix

I'd say the simplest it to just use the rename command which is common on many Linux distributions. There are two common versions of this command so check its man page to find which one you have: ## rename from Perl (common in Debian systems -- Ubuntu, Mint,...

Output from ls has newlines but displays on a single line. Why?

When you pipe the output, ls acts differently. This fact is hidden away in the info documentation: If standard output is a terminal, the output is in columns (sorted vertically) and control characters are output as question marks; otherwise, the output is...

mv: Move file only if destination does not exist

mv -vn file1 file2. This command will do what you want. You can skip -v if you want. -v makes it verbose - mv will tell you that it moved file if it moves it(useful, since there is possibility that file will not be moved) -n moves only if file2 does not exist....

Is it possible to store and query JSON in SQLite?

SQLite 3.9 introduced a new extension (JSON1) that allows you to easily work with JSON data . Also, it introduced support for indexes on expressions, which (in my understanding) should allow you to define indexes on your JSON data as well. PostgreSQL has some...

Combining tail && journalctl

You could use: journalctl -u service-name -f -f, --follow Show only the most recent journal entries, and continuously print new entries as they are appended to the journal. Here I've added "service-name" to distinguish this answer from others; you substitute...

how can shellshock be exploited over SSH?

One example where this can be exploited is on servers with an authorized_keys forced command. When adding an entry to ~/.ssh/authorized_keys, you can prefix the line with command="foo" to force foo to be run any time that ssh public key is used. With this...

Why doesn’t the tilde (~) expand inside double quotes?

The reason, because inside double quotes, tilde ~ has no special meaning, it's treated as literal. POSIX defines Double-Quotes as: Enclosing characters in double-quotes ( "" ) shall preserve the literal value of all characters within the double-quotes, with the...

What is GNU Info for?

GNU Info was designed to offer documentation that was comprehensive, hyperlinked, and possible to output to multiple formats. Man pages were available, and they were great at providing printed output. However, they were designed such that each man page had a...

Set systemd service to execute after fstab mount

a CIFS network location is mounted via /etc/fstab to /mnt/ on boot-up. No, it is not. Get this right, and the rest falls into place naturally. The mount is handled by a (generated) systemd mount unit that will be named something like mnt-wibble.mount. You can...

Merge two video clips into one, placing them next to each other

To be honest, using the accepted answer resulted in a lot of dropped frames for me. However, using the hstack filter_complex produced perfectly fluid output: ffmpeg -i left.mp4 -i right.mp4 -filter_complex hstack output.mp4 ffmpeg -i input1.mp4 -i input2.mp4...

How portable are /dev/stdin, /dev/stdout and /dev/stderr?

It's been available on Linux back into its prehistory. It is not POSIX, although many actual shells (including AT&T ksh and bash) will simulate it if it's not present in the OS; note that this simulation only works at the shell level (i.e. redirection or...

How can I increase the number of inodes in an ext4 filesystem?

It seems that you have a lot more files than normal expectation. I don't know whether there is a solution to change the inode table size dynamically. I'm afraid that you need to back-up your data, and create new filesystem, and restore your data. To create new...

Why doesn’t cp have a progress bar like wget?

The tradition in unix tools is to display messages only if something goes wrong. I think this is both for design and practical reasons. The design is intended to make it obvious when something goes wrong: you get an error message, and it's not drowned in...