Tag: Cron

Chronic and Cron

I had Cron running my recollindex job at the desired time and I had sSmtp set up to email using POP through my gmail email account. The trouble was recollindex gives a lot of output and I was being sent an email with over 22,000 lines in it each time Cron ran the job!

I checked to see if there were command line options I could pass to recollindex to make it run silently or at least more quietly. No joy – recollindex doesn’t support that type of functionality.

I could make it silent by adding a redirect to null on the crontab command line like:

15 01 * * * recollindex >/dev/null 2>&1

But that would mean there would never be any output and there’d never be an email – whether recollindex ran successfully or otherwise.

I Googled a bit and found Chronic. This is a wrapper for Cron jobs. Chronic manages the output from other programs and arranges to only display that output if the command has an error or fails. If the command succeeds, any other output will be  hidden.  And that means no email. So you only get an email if it doesn’t work. Perfect.

To install Chronic type the following into a terminal:

sudo apt-get install moreutils

And to use it in the crontab listing, precede the command you wish to run with chronic, like this:

15 01 * * * chronic recollindex

And to test? Set the time just a few minutes into the future and let it run. You can use top to watch the process list and see that the processes are launched. If it all works according to plan you shouldn’t get an email.

I then changed the command line again so that it would generate an error. I added an extra x to the recollindex command. Because it was spelled incorrectly Cron wouldn’t be able to find a program by that name and that would generate an error. And because there had been an error I should get an email. So I used crontab and changed the line to say:

crontab -e
15 01 * * * chronic recollindexx

Note the extra x. I set the time to a few minutes in the future, let the job run and then checked my email. I had an email with the following subject:

Cron <dave@Nostromo> chronic recollindexx (failed)

and the following content:

Command ‘recollindexx’ not found in /usr/bin, /bin at /usr/bin/chronic line 44

Finally – success! Cron warns me by email if recollindex fails, and only if it fails. (The last step was to go back into crontab and remove the extra x and reset the time to my desired time of 01:15.)

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sSmtp Mail Server

So. I had Recoll working fine and Cron launching recollindex every night at 01:15 to update the index. I wanted to have Cron email me to let me know that recollindex had been launched successfully each night. That was easily achieved by adding the following line to the crontab file:

MAILTO=username@mail.com

I substituted my real email address for the dummy values shown here of course. That told Cron I wanted it to email me. But for Ubuntu to be able to email out it either needs to be set up as an email server or it needs to be able to authenticate against an existing external email server (like Thunderbird does). I didn’t want to have to configure an email server on my Ubuntu PC just for this, so I hunted round for ways to have it authenticate against an external mail server.

Happily, I found sSmtp. sSmtp is an extremely simple, resource conserving, SMTP server that will allow your PC to do just that. It allows processes in your PC to email out, by authenticating against an external mail server. One of my email accounts is a Google mail (gmail) account. I chose to use the gmail mail server as my external mail server.

To install sSmtp type the following into a terminal window:

sudo apt-get install ssmtp

When it had installed I used gedit to edit the ssmtp.conf  file.

gedit /etc/ssmtp/ssmtp.conf

I added or edited the following lines:

root=username@gmail.com
mailhub=smtp.gmail.com:587
rewriteDomain=
hostname=username@gmail.com
UseSTARTTLS=YES
AuthUser=username
AuthPass=password
FromLineOverride=YES

Of course I used my real gmail email adddress details, username and password.

Then I added each account that I wanted to be able to send mail from by editing the revaliases file.

gedit /etc/ssmtp/revaliases

I added two lines, one for root and one for me.

root:username@gmail.com:smtp.gmail.com:587
localusername:username@gmail.com:smtp.gmail.com:587

Again, I used my real gmail email address and my Ubuntu local username.

Now all I had to do was configure gmail to accept POP.

Once I had done that I could test the email throughput by sending an email to one of my other accounts using the following terminal command:

sudo ssmtp otheremail@other.com

Use a real, but different email address than your gmail one.

The message must be formatted in the following way:

To: destination_address@example.com
From: my_email@gmail.com
Subject: Example Message

Cowabunga, Dude!

Bart.

and then hit Ctrl-D. Note the blank line following the Subject: to line. Everything after that is the body of the email. Then go and check your other email account and see if the email got there. If there are any immediate issues, you will see an error message in the terminal window.

If everything has gone according to plan, you should receive the email. It all worked, and that meant that Cron would be able to email me when the recollindex program was launched each night. And that is what happened. In the wee wee hours of the morning I got an email from Cron. All 22,000 lines of it! The output from recollindex is verbose, to understate the matter somewhat.

And that’s what brought me to Chronic.

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Cron and recollindex

Cron is a daemon in Linux systems that runs processes at specified times. A file contains definitions of times and programs. At the specified time it runs the listed program. I wanted to use Cron to launch the recollindex program for me, once a night at 01:15 in the morning. To put entries into the Cron list, you need to use a program called crontab, which maintains the definitions files (cron tables).

You start crontab like this:

crontab -e

I added the following entry at the bottom of the file:

15 01 * * * recollindex

From left to right the tokens mean minutes hours day_of_month month day_of_week.  The asterisks mean unrestricted. So in this example it means run the recollindex program at 01:15 every day, every month. As a test I set the time in the crontab to be a few minutes in the future and used the top command to view the running processes. By watching the process list I could see that the recollindex program was indeed launched and executed at the appropriate time. The system seemed to be working. But how would I know if it had worked every night?

By adding the line:

MAILTO=username@mail.com

You can get Cron to email you when processes are complete. But that meant setting up my Ubuntu system so that applications could email out from it via an SMTP server (Simple Mail Transport Protocol).

And that brought me to sSmtp.

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Recoll Desktop Search

To help me locate an item of interest amongst the ever growing collection of documents, emails, photographs and other data files I have on my computer, I use a desktop search program. Desktop search programs create and maintain an index of the contents of your files. You can specify a word or phrase that you know is in the file and the program will display the list of files that match your search clue. You can preview or open the file from the list of matches.

A good desktop search program will go further. You should be able to specify the file types to include or exclude from a search, and which files and folders to ignore when indexing.

To be really useful the desktop search program needs to be able to burrow through the databases of other applications, such as the email store of Thunderbird, and index the data it finds there. (Actually the search in Thunderbird is very good on its own, but sometimes I need to search for something and see all matching images, documents and emails in one place.)

Recoll
Recoll with search results

The program I’ve settled on in Ubuntu is called Recoll. It is very flexible, it indexes all sorts of files – and the search is fast. Recoll needs to have its index updated periodically to keep it in synch with the changing content of your files. There is a program called recollindex which updates the Recoll index. I didn’t want to have to remember to manually run recollindex, I wanted to find a way to have recollindex started automatically for me.

The answer to that was Cron.

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