[SOLVED] Adding commands in system crontab file to be executed at start up

PaulExordium · 12-23-2021, 08:26 AM

Code:

# non-commented content of /etc/crontab file (Debian 11)

SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin

17 *	* * *	root    cd / && run-parts --report /etc/cron.hourly
25 6	* * *	root	test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.daily )
47 6	* * 7	root	test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.weekly )
52 6	1 * *	root	test -x /usr/sbin/anacron || ( cd / && run-parts --report /etc/cron.monthly )

# added for testing

@reboot		user	date >> $HOME/starts.log
@reboot		user	/usr/bin/firefox-esr
@reboot		user	$HOME/MyApplication

The added commands work fine if run from the terminal but only the first one will be executed at start up, the processes "firefox-esr" and "MyApplication" don't show up.

What am I missing?

pan64 · 12-23-2021, 08:33 AM

At first, cron has its own environment. Especially cron has no any idea about your GUI (and works independently from that). So firefox and MyApp will not find DISPLAY.
Next, crontab will be started before X, so probably firefox and MyApp were started too early.
Finally you need to collect the logs/output of those commands to see what's going on.

michaelk · 12-23-2021, 09:21 AM

pan64 is correct cron is not associated with a terminal or the desktop. To run from cron you need to specify the display i.e.

DISPLAY=:0.0 /usr/bin/firefox-esr

A better solution would be to have your programs run as a startup application i.e. when you log in.

PaulExordium · 12-24-2021, 05:03 AM

If I understand correctly, there is no point in trying to launch a graphic "anything" with "cron" since it was not designed for that. So, after a little learning, I created a "MyApplication.desktop" file in the $HOME/.local/share/appplications" folder and with the "Tweaks" utility added "MyApplication" as a startup application. Easy enough.

Thank you pan64,
thank you michaelk.

pan64 · 12-24-2021, 06:12 AM

Great! If your problem is solved please mark the thread solved. Also if you want to say thanks just click on yes.

djk44883 · 12-31-2021, 09:12 AM

also if you were going to do this, with command which would execute, you need to make sure "user" is in the cron group

pan64 · 12-31-2021, 09:56 AM

Quote:

Originally Posted by djk44883

also if you were going to do this, with command which would execute, you need to make sure "user" is in the cron group

? where is it coming from ? see man crontab:

Quote:

A crontab file contains instructions to the cron(8) daemon of the general form: ``run this command at this time on this
date''. Each user has their own crontab, and commands in any given crontab will be executed as the user who owns the
crontab.

djk44883 · 12-31-2021, 11:29 AM

Mistaken on group I've added myself to group crontab It's easier (maybe not correct) to find and add to cron.d (or /etc/crontab) than crontab -e unless/until you set up an editor...

I can point and click via GUI and use a text editor I'm accustomed with to create files in cron.d (owned by root) generally avoid /etc/crontab as "user" so whatever files are created by "user" and interaction isn't don't by root.

users crontab are deeply buried /var/spool/crontabs/user
Yes each user has their own, in the above example they are using system crontab. Not only the variables won't expand, a user needs to be in the crontab group to even have command executed. The errors should be in cron.log or which ever logging facility is capturing it.

man cron notes Debian specifics "SGID crontab(1) instead of SUID root" and your crontab page notes files are only " This is enforced by having the directory writable only by the crontab group and configuring crontab command with the setgid bid set for that specific group."

It's likely not best practices, it's just my single user system --- it's relative to the OP example even if they had correct commands - user can't run unless they are in group crontab