Hello Garuda users.
I want to do this:
have opt as a subvolume.
(etc/fstab)
UUID=5fbd1add-9f9f9f-492d-bf66-9f61355d7cdc /opt btrfs subvol=/@opt_,noatime,compress=zstd,discard=async,ssd 0 0
I have been doing some research and I understand that I need to create a subvolume
is this the correct way?
sudo btrfs subvolume create @opt
If I reboot in theory this should work fine?
Yes, except you have an underscore after the subvolume name in /etc/fstab which is not in the subvolume name you noted. The rest looks fine.
If there is already content in /opt you should first move it away and then move it into the subvolume, when it is mounted.
I think you would first have to mount your root partition, maybe at /mnt/data, cd to /mnt/data and the run sudo btrfs subvolume create @opt
(etc/fstab)
UUID=5fbd1add-9f9f9f9f-492d-bf66-9f61355d7cdc /opt btrfs subvol=/@opt_,noatime,compress=zstd,discard=async,ssd 0 0
I have been doing some research and I understand that I need to create a subvolume
is this the correct way?
sudo btrfs subvolume create @opt
This way did not work for me it does not start the system
but I did it from the system itself, you are suggesting to do it with a liveusb?
what i want to achieve is that /opt is out of snapshot
It looks like you did not fix the extra underscore, that might be why you aren't able to boot.
If you want to make it a top-level subvolume (instead of a subvolume of /), you can either set it up from a live environment or--perhaps easier--mount subvolid=0 somewhere.
sudo mkdir /mnt/top-level_subvolume
sudo mount -o subvolid=0 /dev/sdx /mnt/top-level_subvolume
cd /mnt/top-level_subvolume
From here, ls should show you your highest-level subvolumes (@, @cache, @home, etc). Go ahead and make your new subvolume.
sudo btrfs subvolume create @opt
This is right. There are a few different ways you can do this, but one fairly simple way would be to mv your existing directory:
sudo mv /opt /opt_old
Make a new directory:
sudo mkdir /opt
Mount the subvolume there:
sudo mount -o subvol=@opt /dev/sdx /opt
Copy all the stuff into it:
sudo cp -ax --reflink=always /opt_old @opt
When you are ready, you can delete opt_old. I would double-check the files are in the new directory and working as expected, everything survives a reboot, et cetera before you do.
Hopefully if I made a mistake someone will chime in with a correction before something gets broken. 
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