Jeg går lidt og drømmer om at bo i kollektiv. Eller bofællesskab. Navnet betyder ikke så meget, men folk har mange (forskellige) værdier knyttet til hvert af de ord og jeg ved derfor ikke altid hvad jeg skal vælge at bruge.

Jeg har haft drømmen nogle år, men det er ikke rigtig blevet til noget. Dels pga. det ikke passede ind i hvor jeg var i livet, dels fordi jeg oplever at det er svært at finde mit drømmekollektiv eller -bofællesskab – og derefter at komme igennem nåleøjet og komme ind. Især hvis man gerne vil bo i eksempelvis Aarhus 🙂

Men nu er det ikke helt min stil at give op, og derfor gør jeg nu forsøget med at søsætte et nyt projekt; et projekt om at skabe det hjem hvor jeg gerne selv vil bo – uanset om det så ender på -tiv eller -skab 😀

Det jeg drømmer om…

… er mange ting, men her er et par af dem 🙂 Jeg er også udmærket klar over at det er svært at få alt. Der er mange kompromiser der skal tages og måske et par kreative løsninger der skal udtænkes. Men altså… her mine drømme:

Som sagt; ovenstående er ikke en kravliste men er mere tænkt til at give et billede af hvad det er for et hjem, jeg drømmer om. Der kan være mange forskellige måder at løse de enkelte ønsker på, og selvfølgelig skal man også være indstillet på at indgå kompromiser når man starter noget fælles op.

Kuppelhuse

I min jagt på det gode hus (og i overvejelserne om at købe eksisterende hus eller bygge nyt) er jeg faldet over kuppelhusene – og blevet lidt forelsket. Derfor vil jeg gerne pitche idéen om at bygge “selv” og at bygge kuppelhuse.

Jeg har haft lidt kig på Easy Domes som en mulighed – jeg synes de er super fede. Lavet i træ, med store vinduer og med højt til loftet – som selvfølgelig kan udnyttes på mange måder.

Easy Domes sælger kuppelhuse i forskellige størrelser. Jeg har leget lidt med at tegne et par kupler ind på en godt 1000m² grund (i Aarhus) for at se hvordan det ser ud:

Der er selvfølgelig mange ting at tage hensyn til – ikke mindst lokalplaner og regulativer – og kuplerne kan helt sikkert placeres bedre end min meget hurtige indsætning. Men tanken er

• 2 “store” kupler (ca. 72m² beboelsesareal) der kan fungere som fællesrum. Dvs. køkken, bryggers, hyggestue, og (selvfølgelig) træningsrum.
• 4 “medium” kupler (ca. 44m²) som kan fungere som beboelse. Medium-kuplerne er stadig høje nok til at kunne have en 1. sal, så jeg forestiller mig at man kan have 2 eller 3 værelser efter behov. Dette kan tilpasses til at huse eks. 2 singler, eller måske en lille familie.
• Jeg er lidt i tvivl om jeg synes det er bedst at have bad/toilet i hvert af beboelseskuplerne, eller om de skal være i fælleskuplerne.

Dette giver et kollektiv-størrelse på 8 personer – måske lidt flere hvis der er børn. Måske lidt færre hvis vi vil prioritere gæsteværelse, et ekstra kontor, eller andet.

Økonomi og alt det praktiske

Der dukker straks en masse spørgsmål op – og mange af dem er der ikke endelige svar på. Det er det vi skal finde ud af sammen. Men jeg har gjort mig et par tanker (over de spørgsmål jeg tænker er klassiske) og svaret lidt løst nedenfor.

Klik på overskrifterne for at se mere.

Jeg er solgt – hvordan kommer jeg med?

Godt spørgsmål og tak fordi du spørger.

Jeg kunne godt tænke mig at etablere en kernegruppe på en 3-4 personer som brænder for dette projekt. Det kommer til at koste noget arbejde. Der skal blandt andet

• Findes fælles enighed om de værdier vi gerne vil bygge på. Det vil formentlig ændre sig lidt undervejs, men det er nok en god idé lige at sætte sig ned og finde et startsted.
• Findes det rigtige sted at bo (by / land).
• Findes det rigtige hus – eller købe ind på at bygge nyt – muligvis kuppelhuse.
• Etableres en økonomisk model – muligvis med stiftelse af en forening.
• Snakkes med bank / realkreditinstitut.
• Snakkes med kommune, arkitekter, rådgivere, byggefirma et al hvis der bygges nyt.

… og derefter kommer alt det kulturmæssige arbejde der følger med når man flytter ind og starter nyt kollektiv.

Men hvis det ikke har skræmt dig væk, så send mig en ansøgning på kollektivetjoanna@mettle.dk¹Tag mig med til et drømmeland… med en kort beskrivelse af dig selv, hvorfor du synes dette projekt er spændende, og hvad du gerne vil bidrage med. Måske også noget om en tidshorisont 🙂

Lidt (mere) om mig

Jeg tænker mange af mine værdier skinner igennem i det ovenstående, men her kommer alligevel en lidt mere formel introduktion af mig.

De obligatoriske kolde facts… 39 år, opvokset på en gård på Als, uddannet ingeniør fra DTU, arbejder med software, har boet 14 år i Kbh og omegn, og har boet i Aarhus siden 2018.

Meget af min fritid har været optaget af akroyoga de senere år; det er en fantastisk idrætsform med styrke, smidighed, koordination, og samarbejde. Akroyoga har givet mig meget socialt – både da jeg boede i København og i mine udlandsrejser – og er også en af grundene til at jeg har taget teten med at undervise hold og startet foreningen Akroyoga Aarhus – altså lige indtil Corona kom og satte det hele på pause.

En anden ting Corona har sat på pause er min elskede cykeltur til/fra arbejdet. Til gengæld har det forgangne år endelig fået sat skub i min morgenbevægelse; altså lidt yoga, håndstand, stræk, let styrke og en smule dans når jeg føler mig fri nok til det 🙂 Jeg håber det er noget jeg kan holde ved og er en af mine motivationspunkter for at få et godt træningsrum i mit næste hjem.

Når jeg ikke render rundt og løfter folk i vejret sætter jeg stor pris på et godt lejrbål, shelterture, MC-ture, foto, klaver og guitar, brætspil og en god øl i ny og næ. På min bogreol står et par bøger af Malcom Gladwell (Tipping Point og Outliers), Kahneman (Thinking – fast and slow), Rosenberg (Nonviolent communication), samt Covey (7 gode vaner). Skønlitterært holder jeg af Asimov (eks. The Complete Robot), Gaiman og Pratchet (eks. Good Omens) og Den lille prins.

Introduction

I recently decided to install Ubuntu Focal Fossa (currently in beta) and test it out. I use my computer(s) a lot – both home and professionally – and I enjoy getting new software installed. It is always exciting to discover new features (and bugs 😖 ) and see what’s been changed.

One of the new features in Focal Fossa is improved ZFS support; it is now possible to use it / enable it right from the installation of Ubuntu. Great ✋. I wanted to give it a go (looking forward to features such as built-in raid support and snapshots) but unfortunately it clashed a little bit with my wish to encrypt my home directory.

While this post is about home directory encryption in a setting of ZFS (and its built-in support of encryption), the general approach may also be of interest to you if you run ext4 and/or other disk encryption tools.

But Why?

Why would you want to encrypt your home directory? Do you have something to hide? Why go through the troubles?

Well… there are a couple of reasons why I chose to do it¹And I am sure there are more…:

• I work as a consultant in IT and it is mandatory (for several reasons) for us to encrypt our data on-disk. E.g. Customer NDAs comes readily to mind.
• While we don’t have private key files for our net banking and government related sites any-more²But have a mobile app for it instead. Perhaps we should pay a bit of attention to security on those devices as well…!, I still have SSH-keys for technical accounts on the net, and for my personal server. And who knows what a skilled hacker could gather of personal information from my web browser cache!?!?
• If my laptop got stolen, I would also like to know that the thief could not readily browse through my personal data (mails, photos, documents, etc.). I believe it is similar to when burglars breaks in to homes: It is not a nice feeling to know that some random stranger has been rummaged through your personal belongings.
• Lastly: Why not? I’m a geek and it’s fun 🙂

Overview – What is the challenge?

The main challenge is two fold:

Ubuntu 20.04 did not provide an option to encrypt your home directory when using ZFS

Ubuntu did previously provide this option, but it used eCryptfs which was considered buggy, under-maintained, [and] not fit for main anymore and has thus been removed.

When enabling encryption manually (after installation) the decrypt action is performed before user login

The issue arises because ZFS is configured (on Ubuntu 20.04) to automatically mount all file systems on the system at boot time – including encrypted home directories. GDM has support for asking for passwords, and hence a prompt appears at boot time. This is great for system wide storage, but not so great for user directories.

PAM to the rescue

PAM is a authentication system that allows programs that rely on authentication to be written independent of the underlying authentication scheme. I.e. if GDM need to authenticate me as a user, it (GDM) can be agnostic about whether my password is in a file on the hard drive or is validated against an AD on the network.

PAM is the Pluggable Authentication Module system in *nix world. If you don’t know it, don’t worry. Neither do I. It is a complex system and I have not had the time (or urge) to really dig in to it other than what I needed here:

We can use PAM to get a hold of the user password when logging in, and in turn use the password to unlock our home directory storage.

So… what we are going to do is:

1. Migrate the home directory from an unencrypted home directory to an encrypted one.
2. Write a small Bash script to assist us in unlocking our home directory.
3. Set up PAM to use the Bash script.
4. Configure properties (used in the unlock script) on our ZFS volume.

Warning – Here Be Monsters

This is the computer-nerdiest post I have written on this site up until now, so if you have not heard of ZFS before, nor are you considering encrypting your home directory, then I am surprised that you got this far in the text 😀

If you continue on this journey with me, then I will assume that you

• Know your way around your Linux system.
• Have the basic knowledge of ZFS (at least read the ZFS man page. Or skimmed it. Or… you know… have heard of it).
• Know your way around Bash scripting.

Here Be Monsters. Messing around your filesystem may lead to data loss. Do back up your data. Proceed at own risk.

Step 1: Migrating the data

It is not possible to encrypt an existing dataset (filesystem) in ZFS once it has been created. Instead one has to make a little (fairly straight-forward) dance to create a new dataset (encrypted right from the beginning) and then move the data.

The command snippets below are examples from my own system; remember that you need to adapt the paths as you go.

1. Create a temporary admin user.
2. Log out of your normal user and log in with the temporary admin user.
3. Move the mount point of your normal user homedir:
   sudo zfs set mountpoint=/home/jvc_nonenc rpool/USERDATA/jvc_tdssc
   Note, here rpool/USERDATA/jvc_tdssc is the existing un-encrypted dataset for my home directory, created by the Ubuntu installation.
4. Really important: Set the property com.ubuntu.zsys:bootfs-datasets as follows:
   VAL=$(zfs get com.ubuntu.zsys:bootfs-datasets rpool/USERDATA/jvc_tdssc -H -ovalue)
sudo zfs set com.ubuntu.zsys:bootfs-datasets=$VAL rpool/USERDATA/jvc_enc
   As described in the Addendum section below, I originally thought this was only needed for automatic snapshotting, but it turns out, omitting this can lead to filesystem deletion!
5. Creat a new encrypted home directory:
   sudo zfs create -o encryption=aes-256-gcm -o keyformat=passphrase -o keylocation=prompt rpool/USERDATA/jvc_enc -o mountpoint=/home/jvc
   Important: Use your normal user password for this encryption, otherwise you won’t be able to decrypt the storage automatically when you log in.
6. Set ownership of new home directory: sudo chown jvc:jvc /home/jvc
7. Copy data from old home directory to new: sudo -u jvc rsync -ar /home/jvc_noenc/ /home/jvc/
8. Make a mental note to clean up (remove) the temporary user and old home directory when all is set and done.

I did the dance and rebooted my computer, and got (as expected) this:

So yes, my home directory was encrypted. Great. But as expected, I now have to enter my password twice: Once during boot for unlocking the storage, and then once more for logging in to the system. This is an issue for me in two ways:

1. I just dislike having to enter my password twice.
2. If my girlfriend should use my computer, then she would not be able to do so without me entering my password at boot time.

Fair enough… most of the time I don’t shut down my computer but only suspends it (like everyone else)… but still…

Step 2: Writing the unlock-mount script

I will just show the script I use here. Assuming that you know how to read Bash, the content is fairly clear (and comments are provided in the code). The properties canmount and dk.talldanestale.automount:user will be explained in step 4.

Save the script to /sbin/mount-zfs-homedir and remember to set the executable bit:

#!/bin/bash

set -eu

# Password is given to us via stdin, save it in a variable for later
PASS=$(cat -)

# List all zfs volumes, listing the *local* value of the property canmount.
zfs get canmount -s local -H -o name,value | while read volname canmount; do
    # Filter on canmount == 'noauto'. Filesystems marked 'noauto' can be mounted,
    # but is not done so automatically during boot.
    [[ $canmount = 'noauto' ]] || continue

    # Filter on user property dk.talldanestale.automount:user. It should match
    # the user that we are logging in as ($PAM_USER)
    user=$(zfs get dk.talldanestale.automount:user -s local -H -o value $volname)
    [[ $user = $PAM_USER ]] || continue

    # Unlock and mount the volume
    zfs load-key "$volname" <<< "$PASS" || continue
    zfs mount "$volname" || true # ignore erros
done

Debug tip: You can change set -eu to set -eux to make Bash print out all commands as it is executing the script. In order to see the output, you also need to enable debug output in PAM. See next step.

Note: The use of here-string (the <<< operator) instead of echo "$PASS" | ... prevents your password from being written to the log.

Step 3: Set up PAM to use the Bash script.

The approach is to use the PAM module pam_exec.so to pass on the user password to an unlock-script.

The PAM configuration is a set of files residing in /etc/pam.d/. Some files are service specific³i.e. named after the service it is relevant to while others are shared (included) by the other files. On my Ubuntu system there is a file named /etc/pam.d/common-auth that is included from other services that enable users to login⁴console login, gdm, ssh etc.. This is the place to add the pam_exec.so hook:

1. Edit the file /etc/pam.d/common-auth:
2. Add the line:

auth optional pam_exec.so expose_authtok /sbin/mount-zfs-homedir

This line can be read as:

1. Set up a hook for user authentication (auth) …
2. that is allowed to fail (optional) …
3. to run a command (pam_exec) …
4. that exposes the password through stdin (expose_authtok).
5. The command to run is mount-zfs-homedir.

That is it for PAM configuration.

Debug tip: If you need to debug things, then adding debug log=/tmp/file.log will help you. Example:

auth optional pam_exec.so expose_authtok debug log=/tmp/file.log /sbin/mount-zfs-homedir

Step 4: Configure properties on our ZFS volume.

The unlock script used two properties, which we will explain and configure here:

Property canmount

The first (substantial) line of the script lists datasets in the zfs pool along with the canmount property. We filter on values noauto. The noauto value indicates to the system that it should not be auto-mounted during boot (which is the trigger for the password prompt at boot).

In other words: We need to mark our home directory not to be auto-mounted at boot:

sudo zfs set canmount=noauto rpool/USERDATA/jvc_enc

Property dk.talldanestale.automount:user

Next, the script is filtering on a custom property dk.talldanestale.automount:user which I use to indicate to which user this dataset (filesystem) belongs. I do not want to attempt to mount my girlfriend’s home directory using my password.

The property is one I created. The ZFS states that user properties must contain a ‘:’, but otherwise is free to choose. I like the concept of prepending (semi) global properties with organization identifier. Hence the dk.talldanestale.

To set the property, execute:

sudo zfs set dk.talldanestale.automount:user=jvc rpool/USERDATA/jvc_enc

That’s it. I hope it helps you on your journey.

Addendum: zsys automatic snapshots

One of the really nice features of ZFS is the snapshot feature. It enables you to, well, take a snapshot on the fly of the filesystem for later use. Later use could be…

• mounting (read-only) for retrieving lost files.
• rolling back system after a failed upgrade or install of a driver.
• a precautionary backup when you are about to perform actions that could potentially result in data loss.

On Ubuntu there is a hook set up in the apt/dpkg configuration that (via zsys) creates a snapshot of the machine just before installing packages. Unfortunately something broke when I created my new home directory and now I would get the error Couldn't find any association for the user dataset ....

Not knowing anything about zsys or how this was set up on Ubuntu I went spelunking and found the property com.ubuntu.zsys:bootfs-datasets that was set on my old home dataset but (of course) not on my new. So… copying this property fixed the issue:

VAL=$(zfs get com.ubuntu.zsys:bootfs-datasets rpool/USERDATA/jvc_tdssc -H -ovalue)
sudo zfs set com.ubuntu.zsys:bootfs-datasets=$VAL rpool/USERDATA/jvc_enc

All done. Hope it helped you as well 🙂

Update March 2021

It turns out that this step (setting com.ubuntu.zsys:bootfs-datasets) is not needed only for snapshotting your new home directory, but also to prevent zsys from deleting it – as happened to Mikhail in the comments below.

It turns out that:

1. zsys considers the namespace USERDATA to be theirs.
2. If a dataset is in that namespace, it will try to manage it.
3. Managing means e.g. taking automatic snapshots of it, but it also means deleting “left over” data sets.
4. If a dataset is in namespace USERDATA but does not have the property com.ubuntu.zsys:bootfs-datasets, then zsys considers it eligible for deletion!

Mikhail filed a bug report to the zsys project. My stance is that it (zsys) should never delete a filesystem unless they are absolute sure that they created it and it is no longer needed. For instance, they could tag a dataset with a zsys-named property (not just namespace USERDATA) and only manage / delete those datasets. Deleting a filesystem on the basis of a missing property is (imho) a bug.

In other words:

• Remember to tag the new dataset!
• If you don’t want it to be managed (i.e. automatic snapshots), choose another namespace than USERDATA.

I was planning a small hiking trip with my girlfriend and a couple of friends when I got a little bit frustrated with the availability of map data for Danish hiking routes and sleeping facilities. Yes! We have great resources, but they all (two I will mention here) have some limitations.

Ud-i-naturen is a great overview of *everything* you could need going out into nature. The trouble is: It is a webpage and as such is not a great user experience on a small touch screen (phone) when you are hiking.

The Shelter App fixes that by being a native app, but it has another problem: It is only showing sleeping facilities and thus you need to correlate the map in the app with either another hiking map app, or a paper map.

What do I want instead?

Well, I have been enjoying Skåneleden for some years while living in Copenhagen. At that time, it was possible to download a KML file with all the tracks and shelters. This, I could import in my Locus Map app and vupti, I would have everything I needed in one view, offline (including map tiles).

Today, Skåneleden has changed strategy a bit. Instead of downloading all of the data, they created an online hiking trip planner – including planning of public transportation out and home. Impressive. You select the tracks you plan to hike, can see distances of each track, filter on difficult level and more. And in the end, you download it as a gpsx file to whatever device you like.

I still prefer the “raw” kml file (or gpsx or ???); anything better than a heavy and clumsy webpage. Yes I know… Smartphones are getting more… powerful (not smart) and internet is more ubiquitous, but still… when hiking, I like the idea of being offline – if nothing else, just to save battery life 😉

Hiking trips on Fyn

So, as I said… I was planning my hiking trip and got frustrated with the situation. I stumbled upon Book-en-shelter where you can get a map of hiking routes on Southern Fyn along with mapping of shelters (across all of Fyn) – but again… no download.

The itchy part for we was… the data is there. You can show/hide tracks and click on shelter locations.

So I took a look at the source and extracted the data into two gpx-files. One for the tracks, and one for the shelters. So… if you like me, like to carry your tracks offline, here is to you:

• Hiking tracks on Southern Fyn
• Shelters across all of Fyn

Note: The data was extracted April 2020. They are not updated here on this site. Please check Book-en-shelter for latest info.

Ps.: If you would like more detailed descriptions of the routes, you can find it on VisitFyn.

I was browsing through Pete Egoscue’s book Pain Free before lending it out to a friend. I feel upon his non-disclaimer and it just resonated with me (again) that I had to share it 🙂

As he writes:

Health care starts with personal responsibility. Any disclaimer that suggests otherwise does a great disservice.

Pete Egoscue – Pain Free

As a small bonus, here is his Eight Laws of Physical Health: