macOS Catalina Boot Volume Layout – The Eclectic Light Company
Note: I’ve now up to date this with the newest roadmaps for 10.15 free up. An additional article will apply on 11 October explaining extra about those.
When you improve to macOS 10.15 Catalina, your boot quantity will successfully be break up into two. Assuming it’s the usual inner garage, your current boot quantity will likely be renamed to Macintosh HD – Data, and a brand new read-only gadget quantity created and given the title Macintosh HD. However, when your Mac begins up in Catalina, you gained’t see the Data quantity, because it’s hidden within the System quantity, in what Apple refers to as a Volume Group.
Although new to macOS, this scheme is already in use in iOS, and specifies the read-only gadget quantity as having the function APFS_VOL_ROLE_SYSTEM, and the writeable consumer quantity has the function APFS_VOL_ROLE_DATA. In that, the amount with the System function is in most cases fastened on the root /, and that containing each consumer and mutable gadget knowledge is then fastened in /System/Volumes and accessed from there the usage of a number of firmlinks.
In this scheme, inode numbers are allotted relative to the foundation, so the information and directories of each volumes percentage the similar quantity inode and quantity house. Thus you’ll be able to’t distinguish the place an merchandise is situated by way of checking its quantity inode. Furthermore, absolute URL paths are given from the foundation listing /, in order that they too don’t disclose which of the volumes within the quantity team an merchandise is saved on.
Inode numbers do make it simple to spot firmlinks: similar to laborious hyperlinks, the 2 directories forming the firmlink have equivalent inode numbers, even though as they’re directories and APFS doesn’t enhance listing laborious hyperlinks, they are able to solely be firmlinks.
A bootable Catalina APFS container in most cases comprises a minimum of 5 APFS volumes:
- the read-only gadget quantity, by way of default at the inner disk named Macintosh HD, which paperwork the foundation of the boot document gadget,
- the writable knowledge quantity, by way of default at the inner disk named Macintosh HD – Data, which is in most cases hidden from view at /System/Volumes and accessed by means of firmlinks,
- Preboot, a small quantity of round 40-50 MB,
- Recovery, the Recovery Volume, of round 500 MB,
- VM, containing digital reminiscence caches, which is upwards of 20 KB relying on use.
Firmlinks are equivalent in some respects to standard symbolic hyperlinks, however are solely made between folders, paintings in each instructions, and with a little bit added magic successfully merge the contents of 2 connected folders. For instance, the /Users listing at the read-only gadget quantity comprises some directories in /Shared. As /Users is a firmlink, the directories there are merged with the ones within the /Users/Shared listing at the writable (Data) quantity.
A equivalent trick applies to the /Applications listing: consumer packages are put in within the Applications listing at the writable quantity; SIP-protected Apple apps are put in in /System/Applications, which is living at the read-only gadget quantity. When you browse the top-level Applications folder within the Finder, you’ll see the mix of each units of apps, with consumer apps connected in the usage of a firmlink between the 2 volumes. Further information about quantity teams and the document gadget magic in Catalina is in this Carbon Copy Cloner KB article.
Layout of same old folders and information at the System quantity is proven on this roadmap:
to be had right here as a PDF: CatalinaSysR
If you need the earlier model, for past due beta releases, right here it’s in PDF: CatalinaSys
Layout of same old folders and information at the Data quantity is proven on this roadmap:
to be had right here as a PDF: CatalinaDataR
If you need the earlier model, for past due beta releases, right here it’s in PDF: CatalineData
The present checklist of firmlinks taken from /usr/percentage/firmlinks is:
/Applications <-> Applications
/Library <-> Library
/System/Library/Caches <-> System/Library/Caches
/System/Library/Assets <-> System/Library/Assets
/System/Library/PreinstalledAssets <-> System/Library/PreinstalledAssets
/System/Library/AssetsV2 <-> System/Library/AssetsV2
/System/Library/PreinstalledAssetsV2 <-> System/Library/PreinstalledAssetsV2
/System/Library/CoreServices/CoreTypes.package/Contents/Library <-> System/Library/CoreServices/CoreTypes.package/Contents/Library
/System/Library/Speech <-> System/Library/Speech
/Users <-> Users
/Volumes <-> Volumes
/cores <-> cores
/decide <-> decide
/personal <-> personal
/usr/native <-> usr/native
/usr/libexec/cups <-> usr/libexec/cups
/usr/percentage/snmp <-> usr/percentage/snmp
in every case proven because the gadget quantity trail and the Data quantity trail which might be firmlinked. These haven’t modified since past due betas.
One treasured trick for at all times the usage of the precise trail in Terminal is to find the folder or document in a Finder window, and drag and drop that into the command line. macOS then magically plays any trail conversions for you. You might also in finding my software Precize helpful, because it offers paths, inode numbers, and an excellent deal extra.
For main points of the jobs and functions of those folders, and the ones inside the Home folder, please refer again to the former article detailing the amount structure of macOS 10.14 Mojave.
Details given listed below are in accordance with exploration of the document gadget of Catalina 10.15 first complete free up.
Amended 1535 UTC 10 October 2019 for the discharge model.