= AutoUpdates

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[IMPORTANT]
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[[automatic-updates]]
Automatic Updates
-----------------

You must decide whether to use automatic link:dnf[DNF] or link:yum[YUM]
updates on each of your machines. There are a number of arguments both
for and against automatic updates to consider. However, there is no
single answer to this question: It is up to the system administrator or
owner of each machine to decide whether automatic updates are desirable
or not for that machine. One of the things which makes one a good system
administrator is the ability to evaluate the facts and other people's
suggestions, and then decide for onesself what one should do.

A general rule that applies in most cases is as follows:

_If the machine is a critical server, for which unplanned downtime of a
service on the machine can not be tolerated, then you should not use
automatic updates. Otherwise, you *may* choose to use them._

Even the general rule above has exceptions, or can be worked around.
Some issues might be resolved through a special setup on your part. For
example, you could create your own dnf|yum repository on a local server,
and only put in it tested or trusted updates. Then use the automatic
updates from only your own repository. Such setups, while perhaps more
difficult to setup and maintain, can remove a large amount of risk
otherwise inherent in automatic updates.

[[how-are-automatic-updates-done]]
How are automatic updates done?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can use a service to automatically download and install any new
updates (for example security updates).

[[fedora-22-or-later-versions]]
Fedora 22 or later versions
^^^^^^^^^^^^^^^^^^^^^^^^^^^

The http://dnf.readthedocs.org/en/latest/automatic.html[dnf-automatic]
RPM package as a link:dnf[DNF] component provides a service which is
started automatically.

[[install-and-settings-of-dnf-automatic]]
Install and settings of dnf-automatic
+++++++++++++++++++++++++++++++++++++

On a fresh install of Fedora 22 with default options the dnf-automatic
RPM is not installed, the first command below installs this RPM.

....
dnf install dnf-automatic
....

Though, you have to change a configuration file. In order to do this,
run as the root user (or become root via su -) from a terminal window.

....
env EDITOR='gedit -w' sudoedit /etc/dnf/automatic.conf
....

Detailed description of dnf-automatic settings is provided on
http://dnf.readthedocs.org/en/latest/automatic.html[dnf-automatic] page.

[[run-dnf-automatic]]
Run dnf-automatic
+++++++++++++++++

Once you are finished with configuration, execute:

`systemctl enable dnf-automatic.timer && systemctl start dnf-automatic.timer`

to enable and start the systemd timer.

Check status of dnf-automatic:

`# systemctl list-timers *dnf-*`

[[changes-as-of-fedora-26]]
Changes as of Fedora 26

As of Fedora 26 there are now three timers that control dnf-automatic.

* dnf-automatic-download.timer - Only download
* dnf-automatic-install.timer - Download and install
* dnf-automatic-notifyonly.timer - Only notify via configured emitters
in _/etc/dnf/automatic.conf_

You can still use _download_updates_ and _apply_updates_ settings from
inside _/etc/dnf/automatic.conf_.

[[fedora-21-or-earlier-versions]]
Fedora 21 or earlier versions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

The yum-cron RPM package provides a service which is started
automatically. Though, you have to change a configuration file. In order
to do this, run as the root user (or become root via su -) from a
terminal window. On a fresh install of Fedora 20 with default options
the yum-cron RPM is not installed, the first command below installs this
RPM.

....
yum install -y yum-cron
env EDITOR='gedit -w' sudoedit /etc/yum/yum-cron.conf"
....

and enter your password. After, change the line

....
apply_updates = no
....

to

....
apply_updates = yes
....

Save the file. You are now done. Yum-cron updates your system every time
when there are new updates available.

[[can-we-trust-dnf-or-yum-updates]]
Can we trust dnf or yum updates?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Dnf and Yum in Fedora has the GPG key checking enabled by default.
Assuming that you have imported the correct GPG keys, and still have
gpgcheck=1 in your for dnf or for yum, then we can at least assume that
any automatically installed updates were not corrupted or modified from
their original state. Using the GPG key checks, there is no way for an
attacker to generate packages that your system will accept as valid
(unless they have a copy of the *private* key corresponding to one you
installed) and any data corruption during download would be caught.

However, the question would also apply to the question of update
quality. Will the installation of the package cause problems on your
system? This we can not answer. Each package goes through a QA process,
and is assumed to be problem free. But, problems happen, and QA can not
test all possible cases. It is always possible that any update may cause
problems during or after installation.

[[why-use-automatic-updates]]
Why use Automatic updates?
~~~~~~~~~~~~~~~~~~~~~~~~~~

The main advantage of automating the updates is that machines are likely
to get updated more quickly, more often, and more uniformly than if they
updates are done manually. We see too many compromised machines on the
internet which would have been safe if the latest updates where
installed in a timely way.

So while you should still be cautious with any automated update
solution, in particular on production systems, it is definitely worth
considering, at least in some situations.

[[reasons-for-using-automatic-updates]]
Reasons FOR using automatic updates
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

While no one can determine for you if your machine is a good candidate
for automatic updates, there are several things which tend to make a
machine a better candidate for automatic updates.

Some things which might make your machine a good candidate for automatic
updates are:

* You are unlikely to apply updates manually for whatever reason(s).
* The machine is not critical and occasional unplanned downtime is
acceptable.
* You can live without remote access to the machine until you can get to
its physical location to resolve problems.
* You do not have any irreplaceable data on the machine, or have proper
backups of such data.

If all of the above apply to your machine(s), then automatic updates may
be your best option to help secure your machine. If not all of the above
apply, then you will need to weigh the risks and decide for yourself if
automatic updates are the best way to proceed.

[[reasons-against-using-automatic-updates]]
Reasons AGAINST using automatic updates
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

While no one can determine for you if your machine is a bad candidate
for automatic updates, there are several things which tend to make a
machine a worse candidate for automatic updates.

Some things which might make your machine be a bad candidate for
automatic updates are:

* It provides a critical service that you don't want to risk having
unscheduled downtime.
* You installed custom software, compiled software from source, or use
third party software that has strict package version requirements.
* You installed a custom kernel, custom kernel modules, third party
kernel modules, or have a third party application that depends on kernel
versions (this may not be a problem if you exclude kernel updates, which
is the default in Fedora dnf.conf or yum.conf files). (But see also
https://bugzilla.redhat.com/show_bug.cgi?id=870790[bug #870790] - you
may need to modify in Fedora 22 or later versions in base section to add
exclude=kernel*. or in Fedora 21 or earlier versions to
exclude=kernel*.)
* Your enviroment requires meticulous change-control procedures.
* You update from other third party yum|dnf repositories besides Fedora
(core, extras, legacy ) repositories which may conflict in versioning
schemes for the same packages.

There are also some other reasons why installing automatic updates
without testing may be a bad idea. A few such reasons are:

* The need to back up your configuration files before an update. Even
the best package spec files can have mistakes. If you have modified a
file which is not flagged as a configuration file, then you might lose
your configuration changes. Or an update may have a different format of
configuration file, requiring a manual reconfiguration. It is often best
to backup your configuration files before doing updates on critical
packages such as mail, web, or database server packages.
* Unwanted side effects. Some packages can create annoying side effects,
particularly ones which have cron jobs. Updates to base packages like
openssl, openldap, sql servers, etc. can have an effect on many other
seemingly unrelated packages.
* Bugs. Many packages contain buggy software or installation scripts.
The update may create problems during or after installation. Even
cosmetic bugs like those found in previous Mozilla updates (causing the
user's icons to be removed or break) can be annoying or problematic.
* Automatic updates may not complete the entire process needed to make
the system secure. For example, dnf or yum can install a kernel update,
but until the machine is rebooted (which dnf or yum will not do
automatically) the new changes won't take effect. The same may apply to
restarting daemons. This can leave the user feeling that he is secure
when he is not.

[[best-practices-when-using-automatic-updates]]
Best practices when using automatic updates
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you decide to use automatic updates, you should at least do a few
things to make sure you are up-to-date.

Check for package updates which have been automatically performed, and
note if they need further (manual) intervention. You can monitor what
dnf or yum has updated via its log file (usually or ).

[[fedora-22-or-later-versions-1]]
Fedora 22 or later versions
^^^^^^^^^^^^^^^^^^^^^^^^^^^

You can monitor updates availability automatically by email after
modifying dnf-automatic configuration file (usually ).

....
[emitters]
emit_via = email

[email]
# The address to send email messages from.
email_from = root@localhost.com

# List of addresses to send messages to.
email_to = root

# Name of the host to connect to to send email messages.
email_host = localhost
....

You would replace root with a actual email address to which you want to
report sent, and localhost with a actual address of SMTP server. This
change will mean that after dnf-automatic runs, it will email you
information you about available updates, or log about downloaded
packages, or installed updates according to settings in .

[[fedora-21-or-earlier-versions-1]]
Fedora 21 or earlier versions
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

You can monitor this automatically by email by modifying the cron job to
mail you the last part of the log file. For example, edit
/etc/cron.daily/yum.cron so that it looks like the following:

....
#!/bin/sh

if [ -f /var/lock/subsys/yum ] ; then
/usr/bin/yum -R 10 -e 0 -d 0 -y update yum
/usr/bin/yum -R 120 -e 0 -d 0 -y update
/usr/bin/tail /var/log/yum.log | /bin/mail -s yum-report youremail@yourdmain
fi
....

You would replace youremail@yourdomain with a actual email address to
which you want to report sent. This change will mean that after yum runs
every night, it will email you the tail end of the log file showing what
happened. (Note this assumes you have a working mail setup on your
machine.)

[[alternative-methods]]
Alternative methods
~~~~~~~~~~~~~~~~~~~

As an alternative to dnf-automatic or yum-cron,
https://github.com/rackerlabs/auter[auter] can be used. This operates in
a similar way to yum-cron, but provides more flexibility in scheduling,
and some additional options including running custom scripts before or
after updates, and automatic reboots. This comes at the expensive of
more complexity to configure.

....
dnf install auter
....

Edit the configuration. Descriptions of the options are contained in the
conf file:

....
/etc/auter/auter.conf
....

Auter is not scheduled by default. Add a schedule for "--prep" (if you
want to pre-download updates) and "--apply" (install updates). The
installed cron job contains lots of examples:

....
/etc/cron.d/auter
....

To make auter run immediately without waiting for the cron job to run,
for example for testing or debugging, you can simply run it from the
command line:

....
auter --apply
....

If you want to disable auter from running, including from any cron job:

....
auter --disable
....

[[alternatives-to-automatic-updates]]
Alternatives to automatic updates
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[[notifications]]
Notifications
^^^^^^^^^^^^^

[[fedora-22-or-later-versions-2]]
Fedora 22 or later versions
+++++++++++++++++++++++++++

Instead of automatic updates, dnf-automatic can only download new
updates and can alert your via email of available updates which you
could then install manually. It can be set by editing of file.

[[fedora-21-or-earlier-versions-2]]
Fedora 21 or earlier versions
+++++++++++++++++++++++++++++

Instead of automatic updates yum can alert your via email of available
updates which you could then install manually. You could accomplish such
a setup with a cron job such as that listed below. Simply put this in
/etc/cron.daily with a suitable filename (such as
yum-check-updates.cron).

....
#!/bin/sh

/usr/bin/yum check-update 2>&1 | /bin/mail -s "yum check-update output" root
....

You can of course change the email address it sends to, etc. to meet
your own needs.

[[scheduling-updates]]
Scheduling updates
^^^^^^^^^^^^^^^^^^

Another common problem is having automatic updates run when it isn't
desired (holidays, weekends, vacations, etc). If there are times that no
one will be around to fix any problem arising the from the updates, it
may be best to avoid doing updates on those days.

[[fedora-22-or-later-versions-3]]
Fedora 22 or later versions
+++++++++++++++++++++++++++

This problem can be fixed by modification of the timer of dnf-automatic
using the description on
https://www.digitalocean.com/community/tutorials/how-to-use-systemctl-to-manage-systemd-services-and-units[Use
Systemctl] page.

[[fedora-21-or-earlier-versions-3]]
Fedora 21 or earlier versions
+++++++++++++++++++++++++++++

One method is to use a crontab entry instead of the
/etc/cron.daily/yum.conf provided by default. For example, to only run
updates from Monday through Friday mornings (avoiding weekends), you
might use a crontab entry such as the following:

....
0 7 * * 1-5   /usr/bin/yum -y update
....

If you need more control over when it runs, you could create a file
called, for example, /usr/local/etc/no-yum-update.conf, which contains a
list of dates not to update on. What dates go in this file is up to you
to decide (vacations, holidays, etc). The dates would be in the format
YYYY-MM-DD (e.g. 2005-03-31). Then create a
/etc/cron.daily/yum-update.cron script something like the following:

....
#!/bin/sh

today=$(date +%Y-%m-%d)

while read banned; do
[ "$today" == "$banned" ]  && exit 0
done < /usr/local/etc/no-yum-update.conf
yum -y update
....

[[other-methods-of-protection]]
Other methods of protection
^^^^^^^^^^^^^^^^^^^^^^^^^^^

Yet another thing to consider if not using automatic updates is to
provide your machine with some other forms of protection to help defend
any attacks that might occur before updates are in place. This might
include an external firewall, a host-based firewall (like iptables,
ipchains, and/or tcp wrappers), not performing dangerous tasks on the
computer (like browsing the web, reading e-mail, etc), and monitoring
the system for instrusions (with system log checkers, IDS systems,
authentication or login monitoring, etc).

'''''

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