[arch-releng] [RFC] Switch from dm-snapshot to overlay

Christian Hesse list at eworm.de
Thu Jul 30 09:53:41 UTC 2015

Gerardo Exequiel Pozzi <vmlinuz386 at gmail.com> on Sat, 2015/07/18 18:18:
> Hello
> Guys, what do you think about switching to overlay filesystem by
> default? This is already implemented around Jan 2015 of this year.

I do not care and I am fine with either of both.

For my own project I do use one of both, depending on what matches my use
case. So please keep support for dm-snapshot in archiso.

> Why?:
> * It seems the most "natural" way.
> * Low RAM usage if user wants do to some changes inside live-enviroment.
> * No crazy crashes if zero-free-space is reached (some bbs/wiki talks
> posts ask about this)
> There is at least two issues at boot time:
> (1) /var/log/journal: Cannot set file attribute for '/var/log/journal',
> value=0x00800000, mask=0x00800000: Inappropriate ioctl for device

Looks like overlayfs is missing some features compared to ext4 and friends.
We had some changes in systemd about filesystem features lately, so is this
still true?

For live systems I tend to set some more journal configuration... What about
adding something like this in /etc/systemd/journald.conf:


> (2) /etc/machine-id: Failed to unmount transient /etc/machine-id file in
> our private namespace: Invalid argument

This happens even if you set the machine-id in initramfs. On an ext4-based
machine I have:

# systemctl status systemd-machine-id-commit.service
● systemd-machine-id-commit.service - Commit a transient machine-id on disk
   Loaded: loaded (/usr/lib/systemd/system/systemd-machine-id-commit.service; static; vendor preset: disabled)
   Active: inactive (dead)
Condition: start condition failed at Thu 2015-07-30 08:29:45 CEST; 3h 19min ago
           ConditionPathIsMountPoint=/etc/machine-id was not met
     Docs: man:systemd-machine-id-commit.service(8)
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