ssmtp to email cron output

Cron output in Ubuntu gets discarded. The default install of Ubuntu does not install a Mail Transport Agent (MTA), so cron cannot mail you the output.

You can install an MTA -several are easily available in the Ubuntu repositories- but configuration is not trivial. MTAs date from before the IMAP- and SMTP-based e-mail systems we use today, which makes them highly flexible and configurable...but not necessarily the easiest solution.

ssmtp is a limited-purpose MTA intended to replace the 'mail' command and send all output to an SMTP mailserver. ssmtp is provided by the 'ssmtp' package.

Install

sudo apt-get install ssmtp

Configuration file #1: /etc/ssmtp/ssmpt.conf

This tells ssmtp how to send email to my account.
It's not the best idea to store your e-mail password in world-readable plain text. See how to protect the password properly.

# Config file for sSMTP sendmail
#
# The person who gets all mail for userids < 1000
# Make this empty to disable rewriting.
root=me@example.com

# The place where the mail goes. The actual machine name is required no
# MX records are consulted. Commonly mailhosts are named mail.domain.com
mailhub=my_mail_server.net:465
AuthUser=me@example.com
AuthPass=my_email_password
UseTLS=Yes

# Where will the mail seem to come from?
rewriteDomain=example.com

# The full hostname
hostname=hey_its_my_computer

# Are users allowed to set their own From: address?
# YES - Allow the user to specify their own From: address
# NO - Use the system generated From: address
FromLineOverride=YES

Configuration File #2: /etc/ssmtp/

This directs root mail to my account.

# sSMTP aliases
#
# Format:       local_account:outgoing_address:mailhub
#
# Example: root:your_login@your.domain:mailhub.your.domain[:port]
# where [:port] is an optional port number that defaults to 25.
root:me@example.com:my_mail_server.net:465

And now cron output lands in my normal inbox.

Moving Cron jobs to Anacron

Cron is a great way to run recurring jobs. But some jobs need to run weekly...and sometimes the computer is turned off, so the cron job doesn't run. So I'm going to migrate some jobs to anacron. Cron runs once each minute, checking if the time matches anything in the crontab list. Anacron, however, runs once each hour (triggered by cron, restart, or resume) and checks the interval in days since a job was last run.

Tips

• Anacron is a root/sudo-level command. Running it as a user will silently FAIL.
• Anacron will silently FAIL to run scripts with periods '.' in the filename.
• Anacron stores the timestamps of each job's last run in /var/spool/anacron/JOBNAME. This is handy to change while testing.

There are two ways to run a command using anacron. You can place the command directly in the anacrontab (/etc/anacrontab), or you can put a script in one of the periodic folders (/etc/cron.daily, /etc/cron.weekly, or /etc/cron.monthly)Here are some examples:

• For comparison, here's an example cron.daily entry that runs at 07:25 each morning:
  

  # min hr dom mon dow   command
  25 07 * * * date > /home/YOUR_USERNAME/.cron/test_file_1

• This /etc/anacrontab entry runs each time anacron is called (days = 0), which is very useful for testing. Start anacron manually with sudo anacron -d.
  

  #days delay  jobname   command
  0 0 anacron-test2  date > /tmp/crontab-test-ouput-everytime

• This /etc/anacrontab entry runs once daily (days = 1), no matter how many times anacron is called automatically or manually.

  #days delay  jobname   command
  1 0 anacron-test3  date >> /tmp/crontab-test-output-daily