[Bug 2048474] [NEW] Subiquity creates far too many zfs file systems

[Hadmut Danisch]

Public bug reported:

I just installed a Xubuntu machine (23.10) with subiquity, choosing ZFS
as a root file system.

Just to install a simple Xubuntu I had no less then two zpools and 25
ZFS file systems right after installation.

Besides the fact, that this is a waste of space (even in ZFS, every file
system occupies some space) and slows the system significantly down,
since every file mv beyond these borders has to be turned into a copy
operation (and thus occupies additional disk space once snapshots
exist), it jams the system and overwhelmes the admin with an avalanche
of file systems, some of them really useless.

Furthermore, it counterfights the intention to have a roll back for the
system, since you really need to synchronize all snapshots (and
technically can't have several filesystems snapshot' at exactly the same
time).

This overload of ZFS filesystems does not make any sense (at least, no
sense I am able to recognize after working intensively and permanently
with ZFS for about 10 years), and I do not see what purpose it should
have to distribute parts of the system onto different file systems,
especially things like having /usr and /var/lib/dpkg on different
filesystems (and thus different snapshots), since /var and /usr *must*
match the state described by /var/lib/dpkg/info/* and apt cache. While
it does make some sense to have things like LXD on a separate ZFS file
system, having /usr and /var/lib/dpkg/info on different ones is a strong
wish for a broken inconsistent system.

Fundamentally, an clean and simple installation should come with just
one ZFS file system, i.e. the root filesystem on /. Maybe /tmp and /home
would be good for a second one, especially if Ubuntu was able to create
a fresh install and leave /home intact or even allow to have different
Ubuntu installations/versions to choose from during boot while sharing
/home or maybe /usr/local.

It does not make much (which?) sense to have two distinct zpools either.
If it's for encryption: ZFS encryption allows to encrypt file systems
and their childred, not just complete zpools.

However, all these extra file systems should only be offered as a option
during installation, part of the manual installation process.

In my eyes, this is merely unusable and looks as if someone not really
experienced more or less just used the examples section of subiquity,
but never actually worked with all that overhead.

Which is sad, since ZFS is one of the best filesystems (if not the best)
Linux currently has to offer.

Proposal:

Create just a single ZFS for /, and leave all others to the admin's
choice during installation.

regards

** Affects: subiquity (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2048474

Title:
  Subiquity creates far too many zfs file systems

Status in subiquity package in Ubuntu:
  New

Bug description:
  I just installed a Xubuntu machine (23.10) with subiquity, choosing
  ZFS as a root file system.

  Just to install a simple Xubuntu I had no less then two zpools and 25
  ZFS file systems right after installation.

  Besides the fact, that this is a waste of space (even in ZFS, every
  file system occupies some space) and slows the system significantly
  down, since every file mv beyond these borders has to be turned into a
  copy operation (and thus occupies additional disk space once snapshots
  exist), it jams the system and overwhelmes the admin with an avalanche
  of file systems, some of them really useless.

  Furthermore, it counterfights the intention to have a roll back for
  the system, since you really need to synchronize all snapshots (and
  technically can't have several filesystems snapshot' at exactly the
  same time).

  This overload of ZFS filesystems does not make any sense (at least, no
  sense I am able to recognize after working intensively and permanently
  with ZFS for about 10 years), and I do not see what purpose it should
  have to distribute parts of the system onto different file systems,
  especially things like having /usr and /var/lib/dpkg on different
  filesystems (and thus different snapshots), since /var and /usr *must*
  match the state described by /var/lib/dpkg/info/* and apt cache. While
  it does make some sense to have things like LXD on a separate ZFS file
  system, having /usr and /var/lib/dpkg/info on different ones is a
  strong wish for a broken inconsistent system.

  Fundamentally, an clean and simple installation should come with just
  one ZFS file system, i.e. the root filesystem on /. Maybe /tmp and
  /home would be good for a second one, especially if Ubuntu was able to
  create a fresh install and leave /home intact or even allow to have
  different Ubuntu installations/versions to choose from during boot
  while sharing /home or maybe /usr/local.

  It does not make much (which?) sense to have two distinct zpools
  either. If it's for encryption: ZFS encryption allows to encrypt file
  systems and their childred, not just complete zpools.

  However, all these extra file systems should only be offered as a
  option during installation, part of the manual installation process.

  In my eyes, this is merely unusable and looks as if someone not really
  experienced more or less just used the examples section of subiquity,
  but never actually worked with all that overhead.

  Which is sad, since ZFS is one of the best filesystems (if not the
  best) Linux currently has to offer.

  Proposal:

  Create just a single ZFS for /, and leave all others to the admin's
  choice during installation.

  regards

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