Category:Admin guides
{{admin_guides}}
Large portions of this guide were taken from Michael W Lucas' ''[https:shop.aer.io/mwl/p/Tarsnap_Mastery_Online_Backups_for_the_Truly_Paran/9780692400203-8826?collection=Technology_Books-177660 Tarsnap Mastery]''. I highly recommend it and anything else he's written.
Installation =
The package is called <code>tarsnap</code> on most distributions and is usually included in the official repos. If it's not, take a look at their [https:www.tarsnap.com/download.html download page]. After installation, generate a key and associate it with your Tarnsap account using the following command.
<pre>
tarsnap-keygen --keyfile /root/tarsnap.key --user name@example.com --machine HOSTNAME
</pre>
Configuration =
The configuration file is usually stored in <code>/etc/tarsnap.conf</code>. You may need to copy the sample configuration to <code>/etc/</code> from elsewhere but it's likely already in the right place. This is what we use but make sure to look at the sample and read the manual before copying and pasting this.
<pre>
cachedir /usr/local/tarsnap-cache
keyfile /root/tarsnap.key
nodump
print-stats
checkpoint-bytes 1G
humanize-numbers
</pre>
Automation =
We use [https:github.com/alexjurkiewicz/acts/ ACTS] for automation. It stands for ''Another Calendar-based Tarsnap Script'' and manages backup creation and rotation. It keeps 31 daily backups, 12 monthly backups, and never deletes yearly backups; maintaining those are on you. When you feel like a specific yearly backup is no longer necessary, delete it yourself.
After adding a new user to our database that has read-only access to everything, we'll create pre- and post-backup scripts for managing database dumps, configure ACTS, then set up email alerts.
Database dumps ==
Refer to SQL Snippets for more quick commands regarding SQL databases.
Setting MySQL up ===
Add a new user with a complicated password and minimal permissions to all databases with the following SQL command.
<pre>
grant lock tables,show view,select on *.* to 'archive'@'localhost' identified by 'CHANGEMETOSOMETHINGSECURE';
</pre>
Setting PostgreSQL up ===
Same as above but PostgreSQL variant; you'll have to repeat these statements after connecting to ''every'' database you want backed up. From what I can tell, there is no way to give a user read-only permission across ''all'' PostgreSQL databases.
<pre>
CREATE ROLE archive WITH LOGIN ENCRYPTED PASSWORD 'CHANGEMETOSOMETHINGSECURE';
\c dbname
GRANT USAGE ON SCHEMA public TO archive;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO archive;
GRANT SELECT ON ALL SEQUENCES IN SCHEMA public TO archive;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON TABLES TO archive;
ALTER DEFAULT PRIVILEGES IN SCHEMA public GRANT SELECT ON SEQUENCES TO archive;
</pre>
Scripting the dumps ===
We store scripts in <code>/usr/local/scripts</code> but you can put them wherever. This one is named <code>/usr/local/scripts/pre-acts.sh</code>. '''''Make sure to change the variables according to your needs.'''''
<pre>
#!/bin/sh
######################################################
# MAKE SURE TO CHANGE VALUES ACCORDING TO YOUR NEEDS #
######################################################
# Create a timestamp for dump names
DAY=$(date +%Y-%m-%d)
# Pick a database server, postgres or mysql
DATABASE=postgres
# Dump file location
DUMPFILE=/root/db_dumps/$DATABASE-backup-$DAY
##########################
# MYSQL-SPECIFIC OPTIONS #
##########################
MYSQLPASSWORD='CHANGEMETOSOMETHINGSECURE'
#############################
# POSTGRES-SPECIFIC OPTIONS #
#############################
# Set the read-only user's password
export PGPASSWORD='CHANGEMETOSOMETHINGSECURETOO'
# Space-separated list of databases for backing up
DBNAME="dbname1 dbname2"
case $DATABASE in
mysql)
touch $DUMPFILE
chown 0:0 $DUMPFILE
chmod 600 $DUMPFILE
mysqldump -u archive -p$MYSQLPASSWORD --all-databases > $DUMPFILE
;;
postgres)
for i in $DBNAME
do
PGDUMP=$DUMPFILE-$i
touch $PGDUMP
chown 0:0 $PGDUMP
chmod 600 $PGDUMP
pg_dump -h 127.0.0.1 -U archive -Fp -n public -O -x -d $i > $PGDUMP
done
;;
esac
exit
</pre>
This one is stored in <code>/usr/local/scripts/post-acts.sh</code>. It deletes all dumps older than 5 days.
<pre>
#!/bin/sh
find /root/db_dumps/ -type f -mtime +5 -delete
</pre>
Make sure these are marked as executable with <code>chmod +x /path/to/script.sh</code>.
ACTS configuration ==
ACTS can be installed by simply <code>wget</code>ing <code>acts</code> and <code>acts.conf.sample</code> directly from [https:github.com/alexjurkiewicz/acts/ the repo]. Alternatively, you can clone the whole repository and symlink <code>acts</code> to wherever you like for easier updates then copy <code>acts.conf.sample</code> to <code>/etc/acts.conf</code>. The following is how we do it.
<pre>
cd /root/
git clone https://github.com/alexjurkiewicz/acts/
ln -s /root/acts/acts /usr/local/scripts/acts
</pre>
Make sure you reference the sample configuration file but these are the base options we use. Add additional directories to the <code>backuptargets</code> line, omitting the preceding <code>/</code>. Until you run ACTS and verify that your configuration works properly, leave <code>verbose</code> set to 1. After you're sure everything works, set it to 0. ACTS expects the config file to be located in <code>/etc/acts.conf</code>
<pre>
backuptargets="usr/local/scripts root/db_dumps"
tarsnapbackupoptions="--one-file-system --humanize-numbers"
verbose=1
prebackupscript=/usr/local/scripts/pre-acts.sh
postbackupscript=/usr/local/scripts/post-acts.sh
</pre>
Cronjob ==
This runs ACTS at 02:30 on every day of every month.
<pre>
# min hour day month weekday command
30 2 * * * /usr/local/scripts/acts
</pre>
Failure notifications ==
We use XMPP for most of our internal communication and have a dedicated MUC for alerts. There are tools such as [https:github.com/lhost/sendxmpp sendxmpp] that allows for piping messages to arbitrary MUCs and contacts. However, that <code>sendxmpp</code> implementation isn't available in all repositories. [https:salsa.debian.org/mdosch/go-sendxmpp go-sendxmpp] is an alternative written in Go that provides pre-built binaries for a large number of platforms.
Download the binary, make it executable, then move it to <code>/usr/local/bin</code>. Put the following script in <code>/usr/local/scripts/alert</code> then make it executable. It takes input from <code>stdin</code>, stores it in a variable, then uses that variable in a message template that contains the cronjob's name and the machine's hostname. All of that is stored in another variable then piped to <code>go-sendxmpp</code>. The <code>go-sendxmpp</code> invocation requires TLS, sets its name to <code>Alert</code>, then relays whatever is passed on <code>stdin</code> to the <code>example@muc.example.com</code> MUC.
<pre>
#!/bin/bash
STDIN=$(</dev/stdin)
MSG="$1 cronjob on $(cat /etc/hostname) just exited.n```n$STDINn```"
echo -e "$MSG" | /usr/local/bin/go-sendxmpp -tr 'Alert' -c example@muc.example.com
</pre>
Before attempting to run the script, create <code>/root/.sendxmpprc</code> with the following contents, replacing USERNAME and PASSWORD with your bot's credentials.
<pre>
username: USERNAME
password: PASSWORD
</pre>
With all of this in place, run the following and see if the setup works.
<pre>
echo 'This is a test' | /usr/local/scripts/alert Test
</pre>
The output should look something like this.
<pre>
18/11/21 | 00:15:41 Alert: Test cronjob on hostname just exited.
This is a test</pre>
If everything works as expected, you can now use it in cronjobs like so.
<pre>
@daily a command to do something 2>&1 | /usr/local/scripts/alert 'Cronjob title'
</pre>
Backups =
Yes, backups for the backups are necessary. Specifically, backups of backup ''keys'' are necessary; if you lose the key, you lose your backups. There is no way around this. While saving your key in a password manager, in a text file on your PC, on someone else's PC (please don't ever do this), or even on another server are all potential solutions, it's good to have an offline copy Just In Case™. We use [https:github.com/intra2net/paperbackup paperbackup] because it's easily read by both machines (QR codes) and humans (plain text); run your key through this, print the resulting PDF, put it in a folder, put the folder in a box, and put the box somewhere very very safe.