Some question regarding btrfs

Hello, I am new to btrfs and have a few questions regarding some of its usages:

  1. The full disk automated Manjaro install creates @, @home, @cache, @log subvolumes in a btrfs parition and a 300 MiB efi partition (with or without swap). But in Fedora 34 automated install, the installer creates a /boot ext4 partition alongside the efi and root btrfs paritions. Is their any advantage of using the separate /boot partition so that one can consider manual installation of Manjaro with ext4 /boot partition rather than just the automated full disk install?
  2. What is the default zstd compression ratio in Manjaro full disk btrfs install?
    [the /etc/fstab has flag compression=zstd, is it zstd:1 compression or something else?]

Again, I am new to btrfs, so pardon me for any stupid question. :sweat_smile:

Well, it’s been a while since I installed Manjaro ─ this system here has been running Manjaro for well over two years now and I’ve never had to reinstall ─ so I’m not sure on the latest GRUB, but GRUB used to have a problem with /boot being on btrfs. I’m guessing that this may have been remedied in the meantime, but my own /boot is still ext4.

Is there an advantage to having a separate /boot? Well, that’s a matter of perspective and personal preference. On my machine, I keep /boot mounted read-only during normal operation ─ I do have to remount it as read/write for updates.

/boot doesn’t need to be big if you don’t keep loads of different kernels around, so it’s not like you’d be wasting space by making it into a fixed partition.

The default compression level is 3.


Thanks a lot for clarifying. :slightly_smiling_face:

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@Shirshendu There may be a problem with external /boot when you try to rollback your system.

If /boot is inside btrfs, the /boot/kernel, /boot/initramfs and /lib/modules do contain the same kernel-version in every snapshot. This is easy to rollback.

If /boot is on another partition this will not be the case. When you rollback you may get in trouble.
Please read further details in:


One advantage is that if you want to use GRUB_SAVEDEFAULT you can’t do that with a btrfs /boot

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in fedora they make two partition for boot. one is efi partition mount in /boot/efi in this they put the UEFI boot files. and other is boot partition mount in /boot they put the kernenl imgfiles, grub files, initramfs files and vmlinuz files. i think this maybe safety.
in manjaro they just make a separate partition /efi mount in /boot/efi,in here put the UEFI boot files.the /boot is not a separate partition just under the root directory

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