Lennart Poettering Announces New Project: casync

[duby229]

It would be pretty stupid getting rid of ISOs. Blank drive, fresh install - ISO becomes mandatory. Unless you are into IMG files, which take often even more disk space. Either way, you need installation media images to get going..

I think you misunderstand, ISO is a standardized format. IMG is just raw data of any kind. It can be whatever you format it as.

[aht0]

I think you misunderstand, ISO is a standardized format. IMG is just raw data of any kind. It can be whatever you format it as.

I've got specific use case in mind. I am using both sorts for OS installs. And there I can't imaging getting rid of ISO's no matter what. IMG files would in this context be just exact software copies of pre-made USB install mediums.

[duby229]

I've got specific use case in mind. I am using both sorts for OS installs. And there I can't imaging getting rid of ISO's no matter what. IMG files would in this context be just exact software copies of pre-made USB install mediums.

Which, imo, is better because it can be formatted in whatever filesystem you prefer.

[ermo]

I tried to read that post about what casync is, and its about as clear as mud. So what does this actually *do*? Is it like Git for binary data with an rsync like interface?

As clear as mud?

- You serialize your data in a nice, reproducible format (akin to tar, but with nicer properties)
- You chop up your serialized data as chunks of variable size based on some clever criteria (smaller files are combined, larger ones chopped up)
- You compress each chunk individually
- You calculate a strong hash of each compressed chunk
- You name each compressed chunk after its strong hash and save it as a file in some directory
- You save the hashes in a linear array index file
- You compare local and remote index files
- You download/upload the missing compressed chunks (each chunk is conveniently named after its hash value, remember?)
- You re-combine the uncompressed chunks in the correct order

I'm not sure I understand what is unclear about that? Did you read the entire article? Or did I miss some obvious sarcasm...?

[TiberiusDuval]

So folks, say I want to ship some version of Ubuntu Mate for Raspberry PI, and want to do push updates to it via the Web later on with possible rollback if things break. What's the best method to do this today?

Hmm something like TrueOS does, it uses ZFS way of snapshot, as far as I know Linux BTRFS can do same. So in Ubuntu case before update snapshot is taken, and relevant, marking in bootloader, then normal apt-get does its work. If update borks whole system, you just load older snapshot.

[starshipeleven]

Hmm something like TrueOS does, it uses ZFS way of snapshot, as far as I know Linux BTRFS can do same. So in Ubuntu case before update snapshot is taken, and relevant, marking in bootloader, then normal apt-get does its work. If update borks whole system, you just load older snapshot.

+1 to this.

Turris Omnia (a high end router made for enthusiasts) uses btrfs to do that and it works fine.
Snapshots on each upgrade and if it does not boot anymore the bootloader tries to boot from an older snapshot. Their uboot (bootloader) has non-mainstream patches to support btrfs, of course.

On a raspi the bootloader is dumb as a bag of bricks and not really modifiable, so this logic will have to be implemented in the kernel/initramfs you leave in the boot partition.

[rabcor]

Ok, I had no idea all that works with alsa & dmix. So you can switch between sinks while the app is running these days? No need to close the browser to switch to bt headphones?

I'm not too clear on the terminology, but changing your default playback device or telling an application to use a specific playback device without restarting anything? yes you can. (But for software to be able to target a specific playback device they must be coded to support it like media players usually are, with options to choose playback devices, otherwise yes, you still have to restart them and set the playback device for it before it is run. But I don't see the problem with that, windows doesn't have the ability to on-the-fly swap out playback devices for applications that do not specifically support it either)

[grok]

It would be pretty stupid getting rid of ISOs. Blank drive, fresh install - ISO becomes mandatory. Unless you are into IMG files, which take often even more disk space. Either way, you need installation media images to get going..

If you don't want isos, there's PXE. Could be worth having pet distros support a PXE installer before going with sync astrophysics. A big offender is linux mint (it supports only the graphical installer run from live desktop anyway. I suppose that simplifies the release process)

[grok]

So folks, say I want to ship some version of Ubuntu Mate for Raspberry PI, and want to do push updates to it via the Web later on with possible rollback if things break. What's the best method to do this today?

Perhaps you should look into Nix OS instead as the package manager itself does atomic commits and rollbacks - it guarantees reproducible changes.

That might be a more useful level than a glorified rsync, cp -a or dd if=network of=/dev/sda on top of some btrfs/zfs/cow thing.
Not sure if it works if you break it so much as to render it completely unbootable but would seem very robust for the rest.

An entirely different feature is FreeBSD boot environments. I'm not qualified to explain what these do but intuitively this seems about snapshotting your boot system so that you can break your computer and not sweat about it. This might have been implicitly referred to with the comment about TrueOS.

[caligula]

I'm not too clear on the terminology, but changing your default playback device or telling an application to use a specific playback device without restarting anything? yes you can. (But for software to be able to target a specific playback device they must be coded to support it like media players usually are, with options to choose playback devices, otherwise yes, you still have to restart them and set the playback device for it before it is run. But I don't see the problem with that, windows doesn't have the ability to on-the-fly swap out playback devices for applications that do not specifically support it either)

Maybe this gives some idea. Possible with Pulseaudio, but does this work with alsa+dmix:

1. boot your computer
2. system loads, initializes alsa, pulseaudio, bluetooth, and sets the builtin sound card as default
3. click the firefox icon and start the browser
4. play a youtube video, sound comes from big speakers connected to internal sound card
5. decide you want to listen to the video via bluetooth headphones. Turn on the headphones.
6. headphones appear as secondary device in volume control, pulseaudio knows you prefer them so it automatically switches all audio currently playing (the youtube video) to bluetooth headphones.
7. start a game. sound goes to headphones right from the start. doesn't matter if the game uses alsa/pulse interface
8. decide you want to share the game sounds with everyone else. Turn off headphones.
9. pulse automatically switches back to internal sound card and sound playback continues from bigger speakers

So this really is possible without pulseaudio?