[flatpak] - I cannot choose or change datadir when running from flatpak

[orsenthil]

flatpak run org.bitcoincore.bitcoin-qt -choosedatadir

The -choosedatadir Should allow me to choose the datadir. But it is not. It immediately starts downloading headers from the peers.
The chooses a predefined datadir in

~/.var/app/org.bitcoincore.bitcoin-qt$ ls
cache  config  data

• I am unable to modify the datadir location when I run the client using flatpak (on PopOS).

To reproduce

1. Install flatpak client
2. try the command

flatpak run org.bitcoincore.bitcoin-qt -choosedatadir

Everytime.

System information

1. PopOS, Flatpak version. Client information

$ flatpak run org.bitcoincore.bitcoin-qt -version
Bitcoin Core version v22.0.0
Copyright (C) 2009-2021 The Bitcoin Core developers

Please contribute if you find Bitcoin Core useful. Visit
<https://bitcoincore.org/> for further information about the software.
The source code is available from <https://github.com/bitcoin/bitcoin>.

This is experimental software.
Distributed under the MIT software license, see the accompanying file COPYING
or <https://opensource.org/licenses/MIT>

[ryanofsky]

I don't know much about the flatpak, but I'm guessing the "flatpak run" command is invoking bitcoin-qt with a hardcoded -datadir= argument that preempts the -choosedatadir argument:

bitcoin/src/qt/intro.cpp

Lines 210 to 213 in 66e2d21

	/* If data directory provided on command line, no need to look at settings
	or show a picking dialog */
	if(!gArgs.GetArg("-datadir", "").empty())
	return true;

Probably easiest way to fix this is for flatpack to stop passing a hardcoded datadir to bitcoin-qt and instead create an initial $HOME/.config/Bitcoin/Bitcoin-Qt.conf file with something like:

[General]
strDataDir=/path/to/datadir

Or, to help with this and make it easier, bitcoin-qt could provide a new softer way of setting a datadir directory that has lower precedence than existing command line and config options like a -defaultdatdir argument or a BITCOIN_DATADIR environment variable.

Assuming flatpak is passing a -datadir argument, it might not be possible to fix this solely in bitcoin-qt without changing the flatpak, because the -datadir argument does take precedence over everything else by design.

[maflcko]

https://github.com/flathub/org.bitcoincore.bitcoin-qt/blob/2d5b49c3ee87bc86f93e75b87512163afd54e284/install_wrappers.sh#L6

[ryanofsky]

https://github.com/flathub/org.bitcoincore.bitcoin-qt/blob/2d5b49c3ee87bc86f93e75b87512163afd54e284/install_wrappers.sh#L6

Thanks. Since that wraps both bitcoind and bitcoin-qt, it looks like a similar problem would also happen with bitcoind and the -conf option. For example if user tried to use the flatpak with -conf argument and a configuration file containing datadir=/some/path, the configured datadir would be ignored because of the flatpak command line argument.

Maybe a decent way to fix these issues across all the binaries could be to make GetDefaultDataDir check for a BITCOIN_DATADIR environment variable, and change the flatpak to set BITCOIN_DATADIR instead of passing -datadir=

Having the wrapper create an initial Bitcoin-Qt.conf as suggested previously could also work to fix the GUI problem, but seems more awkward.

[orsenthil]

@MarcoFalke - Interesting. the change /setup was in the flathub/org.bitcoincore.bitcoin-qt repo, while the issues page led me here.

That said, yes. I found it impossible to configure anything or provide datadir during startup while running from flatpak.

[ryanofsky]

That said, yes. I found it impossible to configure anything or provide datadir during startup while running from flatpak.

You should still be able to override the datadir from the command line by appending your own -datadir argument.

[orsenthil]

I had tried that. I gave an option a different datadir, which I had moved, and run didn't recognize. I will try again and share the output.

I ended up using a non flatpak version - compiled from the master of this repo.

[ryanofsky]

Sounds good. I think we have enough information to fix this in any case.

Another possible option if flatpak supports this could be to put a symlink in the flatpak datadir location that points to the desired location

[orsenthil]

I tried the symlink option too. I moved the datadir from ~/.var/app/org.bitcoincore.bitcoin-qt and ln -s that data dir; but the flatpak run complained (something like datadir doesn't exist).

[nolajohn]

This worked for me - Pop!_OS (Ubuntu 22.04 LTS) running bitcoincore installed via flatpak:

Get the flatpak ID:

> flatpak list | grep -i bitcoin
> Bitcoin Core	org.bitcoincore.bitcoin-qt	26.1	stable	user

Allow flatpak to use the new data folder:

> flatpak override --user --filesystem=/my/new/folder/for-btc-data org.bitcoincore.bitcoin-qt

Launch from the command line:

> flatpak run org.bitcoincore.bitcoin-qt --datadir=/my/new/folder/for-btc-data &

I have to launch from the command line. Editing the flatpak .desktop file does not work.

[laanwj]

Allow flatpak to use the new data folder:

> flatpak override --user --filesystem=/my/new/folder/for-btc-data org.bitcoincore.bitcoin-qt

This is the correct solution. Flatpak applications are sandboxed, and there's nothing bitcoin-qt can do to reach outside that, unless given explicit permission.

After giving it permission, as above, you should be able to use the qt chooser dialog to pick the datadir, so that it gets picked automatically in the future:

> flatpak run org.bitcoincore.bitcoin-qt -choosedatadir &

If that never shows the datadir picker with flatpak, that's a bug. It is.

[laanwj]

I don't know much about the flatpak, but I'm guessing the "flatpak run" command is invoking bitcoin-qt with a hardcoded -datadir= argument that preempts the -choosedatadir argument:

Looks like you're right. Flatpak creates a wrapper script that simply passes -datadir unconditionally.
https://github.com/flathub/org.bitcoincore.bitcoin-qt/blob/master/install_wrappers.sh

There would be multiple ways to solve this. One way to fix it without changes to this repository would be to adapt the script so that when -choosedatadir is passed, or an explicit -datadir,, it doesn't pass the argument.