manual: clarify volume creation section

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Daiderd Jordan 2020-03-26 20:14:08 +01:00
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@ -141,13 +141,14 @@ sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
<para>
The root filesystem is read-only as of macOS 10.15 Catalina, all writable
paths to a separate data volume. This means creating or writing to <filename>/nix</filename>
is not allowed. While changing the default prefix would be possible, it's
a very intrusive change that has side effects we want to avoid for now.
paths were moved to a separate data volume. This means creating or writing
to <filename>/nix</filename> is not allowed. While changing the default prefix
would be possible, it's a very intrusive change that has side effects we want to
avoid for now.
</para>
<para>
For common writable locations <literal>firmlinks</literal> where introduced,
For common writable locations <literal>firmlinks</literal> were introduced,
described by Apple as a "bi-directional wormhole" between two filesystems.
Essentially a bind mount for APFS volumes. However this is (currently) not
user configurable and only available for paths like <filename>/Users</filename>.
@ -156,8 +157,10 @@ sudo rm /Library/LaunchDaemons/org.nixos.nix-daemon.plist
<para>
For special cases like NFS mount points or package manager roots <link xlink:href="https://developer.apple.com/library/archive/documentation/System/Conceptual/ManPages_iPhoneOS/man5/synthetic.conf.5.html">synthetic.conf(5)</link>
provides a mechanism for some limited, user-controlled file-creation at <filename>/</filename>.
This only applies on a reboot, but <command>apfs.util</command> can be used
to trigger the creation (not deletion) of new entries.
This only applies at boot time, however <command>apfs.util</command> can be used
to trigger the creation (not deletion) of new entries without a reboot.
It would be ideal if this could create firmlinks, however a symlink or mountpoint
are the only options.
</para>
<screen>