Proposal for a improved software distribution using BTRFS

[Feathers McGraw]

I can't get a Jolla phone because...ANYWAY - I have a Jolla Tablet on order (Indegogo early contributor ) so at least I have that.

I know this was a long time ago, but I was thinking about this again earlier. I'm guessing you haven't received your tablet yet, but did you ever try putting Sailfish on another device? Asking because the N5 port is discussed quite a lot on TMO, and I was wondering if anyone outside that particular echo chamber had actually tried it?

[InsideJob]

I installed openSuSE from some magazine last month and my root partition was BTRFS. The home partition was XFS for some reason though. And of course EFI boot had to be FAT. That's too many partition types for me.

[Feathers McGraw]

OK, Now I'm ticked. I can't get a Jolla phone ... I have a Jolla Tablet on order

I've had my Jolla for 3 days now, it's just what I wanted. When I'm using my Nexus 7, I sometimes find myself trying to swipe it to close/minimise apps. Annoying to have to move your hand to the bottom edge to go back, too. The UI of Sailfish is really nicely thought out, although it seemed a little strange at first. I'd be interested to see how you get on with it on a N4.

I think you'll really like the tablet. Lots of cool software already, the selection on the Jolla store doesn't do it justice - a lot of the best stuff is actually at https://openrepos.net/ because of Jolla's packaging requirements (no daemons, no extra libs installed outside of the app directory etc.).

I was pleasantly surprised to find an excellent open source pebble daemon (link) on there. It has a nice GUI for configuration, can load and unload apps from the pebble, forward all notifications, even lets you control music apps that support the MPRIS DBus interface (like Sirensong) from the watch. Basically, it does everything the official Pebble app for Android does, and it's open source to boot. Clever devs!

I expected to need the Android support, but I haven't installed it yet. So far, there has been a high quality native app for everything I need. The one thing I think I might install it for is a banking app, but that's it.

They've done a really good job so far, I hope they can keep it up.

BTW, on the first day I had a hiccup when updating Sailfish to a newer version. Device booted but no UI. To get to recovery, you just hold volume down during boot and plug it in to a computer with a USB cable. It appears as an ethernet device, network manager auto-connects... telnet to it to get a simple menu, 30 seconds later I've reset it and no more problems. That was a BTRFS snapshot - you win! Lol.

[SteveRiley]

I'm trying to convince my wife to give up her Nexus 4 so I can put Sailfish on it...

Sell ya mine...not using it now that I got a Galaxy Note 4.

[claydoh]

Yeah Clay - perfect use case for btrfs. Get a 64 GB thumb drive for backups and build that pool!


Uhhh... not the summer time swimming thing - the data-in-a-pile thing...

Oh, I need a pool. It has been steamy and hot down here in Savannah since, what, March? Been swimming in sweat the past few weeks in particular, and I had to actually put on long pants for court , first time since last winter (2014's, that is) that my calves have not seen the sun.

[oshunluvr]

Now that is useful, and for me in particular. My 64GB ssd gets a bit tight on / all the time. And an extra backup method is always useful.

Yeah Clay - perfect use case for btrfs. Get a 64 GB thumb drive for backups and build that pool!


Uhhh... not the summer time swimming thing - the data-in-a-pile thing...

[oshunluvr]

I just discovered that the Jolla smartphone uses BTRFS. I had a feeling it might, because it seems to support a lot of new Linux things (Wayland by default, systemD etc).

I ordered one last week when it became clear that The Other Half Keyboard isn't just vapour-ware and will actually materialise soon, so it looks like I'll definitely be learning about BTRFS

OK, Now I'm ticked. I can't get a Jolla phone because I live in damn America where corporations rule and consumers are sheep - and for some reason our fugin congress thinks that's OK. ANYWAY - I have a Jolla Tablet on order (Indegogo early contributor ) so at least I have that. I'm trying to convince my wife to give up her Nexus 4 so I can put Sailfish on it...

[claydoh]

I see a couple real-world best use cases for btrfs and an average Джо:

A single small SSD: The need for a partitioning goes away when you use btrfs. Simply create and delete subvolumes at will and mount them as though they were partitions. The real advantage here is all the free space is part of the pool so your root, home, data, spare, backup, whatever "partitions" now share the free space and take it when they grow. No advance guessing how many gig's will be need for root, etc. If you have a 2TB drive, who cares if you waste a dozen GBs or even more? You don't even notice. But with a 64GB ssd, you might regret partitioning 20GB for your install only to find yourself using only 8GB of it. He makes his on-line backups with snapshots and off-line backups (btrfs send/receive) to a USB drive to the cloud or over his network to a server.

Now that is useful, and for me in particular. My 64GB ssd gets a bit tight on / all the time. And an extra backup method is always useful.

[Feathers McGraw]

I just discovered that the Jolla smartphone uses BTRFS. I had a feeling it might, because it seems to support a lot of new Linux things (Wayland by default, systemD etc).

I ordered one last week when it became clear that The Other Half Keyboard isn't just vapour-ware and will actually materialise soon, so it looks like I'll definitely be learning about BTRFS

[oshunluvr]

Yeah, right? 'Cause you have nothing else to do...

[Feathers McGraw]

I guess a direct answer to your query is: A file is not deleted (space freed) until itself and all the snapshots of it are deleted. One advantage here is subsequent snapshots of a subvolume don't re-duplicate data. In other words, six snapshots of your home don't contain six copies of a file you deleted from the original subvolume, only one copy is saved. Once the original and all the snapshots containing the file reference are deleted - the space is freed.

Thanks, I understand now

BTRFS just moved up my "to do" list

[dibl]

It's really about tolerance for potential calamity. If your house burns down, you better have a backup elsewhere.

Well said. And that tolerance varies greatly among individuals (and perhaps organizations). Personally, these days I don't add a lot of new data in an hour or a day or even a typical week. But there's 25 years' of research work, digitization of music and images, correspondence, and records of various kinds sitting here spinning on disks. So it's not important to get a daily or even a weekly backup under my circumstances -- the cost of recreating (or foregoing) that much new work is small. But my occasional full backups go onto one of a rotating set of 1T hdds, and off to a trusted relative's house for safekeeping in the event of disaster. I can't tolerate even the tiniest chance of a total loss, even though I can easily tolerate the chance of a small loss.

[oshunluvr]

Disk full conditions have the same effect they always do. A full disk doesn't allow more writes to it until it's no longer full. You would have to delete some data - snapshot or otherwise - before continuing.

I guess a direct answer to your query is: A file is not deleted (space freed) until itself and all the snapshots of it are deleted. One advantage here is subsequent snapshots of a subvolume don't re-duplicate data. In other words, six snapshots of your home don't contain six copies of a file you deleted from the original subvolume, only one copy is saved. Once the original and all the snapshots containing the file reference are deleted - the space is freed.

I guess the difference is that with a conventional backup all the files are duplicated thus the space used is doubled. With a snapshot, while held within the same pool as the source subvolume, no additional space is used until and unless there is a change to a file(s) on the source subvolume.

You can determine the amount of unique space a snapshot holds by enabling quota on your btrfs filesystem and running a qgroup list. The quota feature is still under development so it is not advised to leave it active all the time - only when needed.

As Steve points out - snapshots aren't really backups in the traditional sense. At least until you send it to a different pool.

[Feathers McGraw]

All of this seems to rely on old versions of files still existing on the disk somewhere.

I understand that if not all of the drive is in use you can delete an old file and write a new one to a different physical location on the disk without destroying the old file (just removing the "pointer" to it)... but what happens if your disk is quite full?

At some point you will need to re-use the parts of the disk that still contain "old" or deleted files, does this break a BTRFS snapshot?

[oshunluvr]

A snapshot is not a backup -- what happens when the pointed-to data ceases, for some calamitous reason, to exist?

Somewhat true - just like any backup - it depends on your level of need for protection. A snapshot is more protection than nothing and super quick and simple and as dibl and I have stated - we've yet to see a calamitous event at the filesystem level since 2010 using btrfs.

It's really about tolerance for potential calamity. If your house burns down, you better have a backup elsewhere. Others might consider that if one's house burns down, you'd have larger problems than having to rebuild a spreadsheet. So therefore, different levels of need for backups exist. A snapshot will protect you from a deletion or corruption (at the userspace level), but not a device failure. A separate device backup will protect you from a hard drive failure, but not a house fire. Pictures of my kids exist in both digital format and print (some anyway) so do I make hard copies and have them in a safe deposit box or fireproof safe? No, because life would go on without those pictures.

I suppose another factor in backups is cost of creation - both in workload and money. An automatic, free, and reasonably flawless backup system should always be chosen no matter what the value of the data - why not, right? Like Google backup of your cell phone contacts, messages, pics, even a list of what you've installed - happens without user input (time or money), all you have to do is opt in. You'd be crazy not to take it. But paying for a service that requires you to remember to use it and takes your time? Maybe you wouldn't care that much about your text messages.

Anyway - back to the snapshot: A snapshot is a backup - albeit at a rather low level. If you need it a higher level of backup - use send/receive to another device of that same snapshot (still happens without much effort - just takes longer). If you need a still higher level - better get a cloud service.