Intro

Back­ups are im­por­tant ok? I know that. You should know that. So, why don't most peo­ple do prop­er back­ups of their com­put­er­s?

Be­cause most of the ways to do back­ups are ei­ther in­con­ve­nient or use­less.

So, here's how the so­lu­tion I have im­ple­ment­ed that makes back­ups con­ve­nient and use­ful.

The backup tool itself

I use restic be­cause it kicks as­s. It work­s, it's fast, it's space ef­fi­cien­t, and it's easy.

You just need to write a short script like this one:

#!/bin/bash -x

# Where to backup?
MOUNTDIR=/backup
BACKUPDIR=$MOUNTDIR/backup-$HOSTNAME

if [ -d $BACKUPDIR ]
then
    # Backups are password protected
    export RESTIC_PASSWORD=passwordgoeshere

    # What to backup
    restic -r $BACKUPDIR --verbose backup \
            /home/ralsina \
            --exclude ~ralsina/.cargo \
            --exclude ~ralsina/.local/share/Steam/ \
            --exclude ~ralsina/.cache \
            --exclude ~ralsina/.config/google-chrome/ \
            --exclude ~ralsina/.rustup \
            --exclude ~ralsina/.npm \
            --exclude ~ralsina/.gitbook \
            \
            /etc/systemd/system/backup.* \
            /usr/local/bin

    # Keep at most one backup for the last 7 days that have backups
    restic -r $MOUNTDIR/backup-pinky forget --prune --keep-daily=7
    # Cleanup
    restic -r $MOUNTDIR/backup-pinky prune
    # Make really sure things are stored
    sync; sync; sync; sync
fi

Backup rule 3-2-1

The 3-2-1 rule:

• 3 copies of the back­up da­ta (1 pri­ma­ry, 2 copies)
• 2 dif­fer­ent me­dia
• 1 must be off­site

In my case, these are:

• Pri­ma­ry back­up is to disk
• Sec­ondary back­up is to a disk in an­oth­er ma­chine (sim­i­lar scrip­t, us­ing sftp)
• Ter­tiary back­up is to a pen drive (d­if­fer­ent me­di­a) I then put in my pock­et (off­site).

To per­form the pri­ma­ry and sec­ondary back­up­s, it's just two slight­ly dif­fer­ent ver­sions of that script (ac­tu­al­ly, it's just one script with ar­gu­ments, left as an ex­er­cise for the read­er).

The ter­tiary back­up is a bit more com­pli­cat­ed, be­cause I want­ed it to be con­ve­nient

The Convenient Way To Backup to a Removable Drive

My us­er sto­ry was this:

As a per­son that needs an off­site back­up but don't want to trans­mit all that data, I want to plug a pen drive in­to the ma­chine and have it AU­TO­MAT­I­CAL­LY start back­ing the da­ta in­to the pen drive.

Then, once the back­up is fin­ished, at some point, I can just un­plug it and take it with me.

Let's just say that find­ing a way that works took me a few hours and I am pret­ty sure my so­lu­tion is more com­pli­cat­ed than it needs to be. But hey, it work­s, so it's good enough.

This be­ing Lin­ux and the year be­ing 2022 ... this so­lu­tion in­volves sys­temd. And be­cause it's sys­temd, it's com­pli­cat­ed.

Automount

First part is we need to mount the pen drive automatically in a well known location. For this we need two things. An automount service, so systemd will automatically mount something in /backup:

/etc/systemd/system/backup.automount

[Unit]
Description=Automount Backup

[Automount]
Where=/backup
TimeoutIdleSec=5min

[Install]
WantedBy=multi-user.target

And a mount service so it knows what to mount in /backup and how:

/etc/systemd/system/backup.mount

[Unit]
Description=Backup
Wants=backup.service
Before=backup.service

[Mount]
What=/dev/disk/by-uuid/74cac511-4d7a-4221-9c0f-e554de12fbf1
Where=/backup
Type=ext4
Options=auto

[Install]
WantedBy=multi-user.target

The in­ter­est­ing parts are:

• Wants and Before: that backup.service is going to be a systemd service that actually runs the backup script. We want it to run, and to run AFTER the device is mounted.
• Where and What: Where is the mountpoint, and What is the pen drive's UUID as shown by sudo blkid

En­able and start the au­to­mount ser­vice, no need to do any­thing to the mount one.

Then of course we need the back­up ser­vice it­self. Just a "oneshot". When it's start­ed, it runs the back­up scrip­t:

/etc/systemd/system/backup.service

[Unit]
Description=Backup
Requires=backup.mount
After=backup.mount

[Service]
Type=oneshot
ExecStart=/usr/local/bin/backup.sh

[Install]
WantedBy=multi-user.target

En­able but don't start this ser­vice. Since it's "Want­ed" by the moun­t, that means when the de­vice is ef­fec­tive­ly mount­ed the back­up will start.

OR THAT WOULD IT DO IF THINGS MADE SENSE.

Sadly, the device is only mounted when, after being inserted, something tries to use the mountpoint. So, with these three services installed nothing happens unless, after you plug the pen drive you go and do something like ls /backup, which triggers the mount, which triggers the backup script.

So, how does one fix that? No idea. My workaround was to add TWO MORE SERVICES, so that ls /backup runs every minute.

/etc/systemd/system/backup_try.timer

[Unit]
Description=Try to run backup

[Timer]
OnUnitActiveSec=1min

[Install]
WantedBy=timers.target

/etc/systemd/system/backup_try.service

[Unit]
Description=Trigger Backup

[Service]
Type=oneshot
ExecStart=/bin/ls /backup

[Install]
WantedBy=multi-user.target

And with that, yes, I can just plug the pen drive when I get to the of­fice in the morn­ing and un­plug it lat­er, know­ing there is a back­up in it.