Setup monthly ZFS scrubs with email alerts on Ubuntu Server 22.04

Published: 2023-02-03 · Last modified: 2023-02-03

A preliminary note of caution

I would advice against using email alerting for anything industry or mission critical, as email has issues with reliability among other things.


ZFS is installed and configured, (install ZFS on Ubuntu Server).

Install msmtp and dependencies

msmtp is an SMTP client that is simple and easy to configure.

Fetch the latest version of the package list:

sudo apt update

Install msmtp along with msmtp-mta and mailutils:

sudo apt install -y msmtp msmtp-mta mailutils

Configure msmtp

Edit the /etc/msmtprc file (with root privileges), you can do this on Ubuntu using the sudoedit command:

sudoedit /etc/msmtprc

Note: You can easily change the sudoedit editor by setting the SUDO_EDITOR environment variable.

Edit the /etc/msmtprc file:

# Set default values for all following accounts.
auth           on
tls            on
tls_starttls   on
tls_trust_file /etc/ssl/certs/ca-certificates.crt

# Outlook.
account        outlook
port           587
password       very_secret_password

# Gmail.
account        gmail
port           587
password       much_different_password

Note: In this example, I have added templating for sending emails over TLS using either Gmail or Outlook. You can add other accounts by following the same format, (the account variable is required, but its value does not matter, it will not be used as an identifier).

Install ZED

ZED (ZFS Event Daemon) listens for ZFS events, and it can be configured to send email alerts after automated scrubs.

Install ZED:

sudo apt install zfs-zed

Configure ZED

Edit the ZED config file /etc/zfs/zed.d/zed.rc:

This configuration file is a little long, so I have included the relevant lines below. First up, the recipient email address of the alerts is set:

# Email address of the zpool administrator for receipt of notifications;
#   multiple addresses can be specified if they are delimited by whitespace.
# Email will only be sent if ZED_EMAIL_ADDR is defined.
# Disabled by default; uncomment to enable.

Then the mail command is set:

# Name or path of executable responsible for sending notifications via email;
#   the mail program must be capable of reading a message body from stdin.
# Email will only be sent if ZED_EMAIL_ADDR is defined.

Then the command-line options for the mail command is set:

# Command-line options for ZED_EMAIL_PROG.
# The string @ADDRESS@ will be replaced with the recipient email address(es).
# The string @SUBJECT@ will be replaced with the notification subject;
#   this should be protected with quotes to prevent word-splitting.
# Email will only be sent if ZED_EMAIL_ADDR is defined.

Note: The e-mail address after -r will determine the sender address of the alert email.

Finally (and optionally), the alerting verbosity is set, setting it to 1 will send alerts regardless of the pool health:

# Notification verbosity.
#   If set to 0, suppress notification if the pool is healthy.
#   If set to 1, send notification regardless of pool health.

Note: If you want to test the email alerts, set this variable to 1.

[Optional] Configure ZED scrubbing schedule

Interestingly, ZED on Ubuntu and Debian is pre-configured to perform a scrub on the second Sunday of each month (not a 🐛).

This feels like a pretty sane default, but if you want to change it, you can do so by editing the /etc/cron.d/zfsutils-linux file.


# Scrub the second Sunday of every month.
24 0 8-14 * * root if [ $(date +\%w) -eq 0 ] && [ -x /usr/lib/zfs-linux/scrub ]; then /usr/lib/zfs-linux/scrub; fi

Note: This does a scrub on all ZFS storage pools. You can alternatively also delete the /etc/cron.d/zfsutils-linux file and configure a (root) cron job for each pool individually.

[Optional] Test ZFS scrub email alerts

If you want to test the email alerts, you can do so by creating a small ZFS test pool, scrubbing it, and then discarding it (source).

cd /tmp
dd if=/dev/zero of=zpool_test bs=1 count=0 seek=512M
sudo zpool create test /tmp/zpool_test
sudo zpool scrub test
sudo zpool export test
rm /tmp/zpool_test

Note: ZED_NOTIFY_VERBOSE=1 must be set in the ZED config file for this to work.