macOS Catalina: incorrect permissions on /tmp directory I've recently initialized my MacBook Pro 10.2 restoring from a TimeMachine Backup. It installed macOS Catalina GM on a Beta (Not sure about that, but now I got version 19B77a (10.15.1).

After this installation, there are problems installing applications or updating etc. 

After some investigation I've discovered that the system is unable to write the /tmp directory.

I've tried to made an ls to the / directory:

$ ls -lah /
total 9
drwxr-xr-x   22 root  admin   704B Feb 12 22:16 .
drwxr-xr-x   22 root  admin   704B Feb 12 22:16 ..
-rw-rw-r--    1 root  admin     0B Oct  8 07:20 .DS_Store
lrwxr-xr-x    1 root  admin    36B Feb 12 22:14 .VolumeIcon.icns -&gt; System/Volumes/Data/.VolumeIcon.icns
----------    1 root  admin     0B Oct  8 07:20 .file
drwx------    7 root  admin   224B Apr  3 19:46 .fseventsd
drwxr-xr-x    2 root  wheel    64B Oct  8 07:20 .vol
drwxr-xr-x+ 144 root  admin   4.5K Apr  3 08:02 Applications
drwxr-xr-x   64 root  wheel   2.0K Mar 11 17:57 Library
drwxr-xr-x@   8 root  wheel   256B Oct 15 07:37 System
drwxr-xr-x    5 root  admin   160B Feb 13 01:22 Users
drwxr-xr-x    4 root  wheel   128B Apr  3 19:50 Volumes
drwxr-xr-x@  38 root  wheel   1.2K Oct 15 07:46 bin
drwxr-xr-x    2 root  wheel    64B Aug 24  2019 cores
dr-xr-xr-x    3 root  wheel   4.2K Apr  3 19:46 dev
lrwxr-xr-x@   1 root  admin    11B Feb 12 22:06 etc -&gt; private/etc
lrwxr-xr-x    1 root  wheel    25B Apr  3 19:50 home -&gt; /System/Volumes/Data/home
drwxr-xr-x    6 root  wheel   192B Feb 13 01:22 opt
drwxr-xr-x    6 root  wheel   192B Feb 13 01:22 private
drwxr-xr-x@  64 root  wheel   2.0K Feb 12 22:14 sbin
lrwxr-xr-x@   1 root  admin    11B Feb 12 22:14 tmp -&gt; private/tmp
drwxr-xr-x@  11 root  wheel   352B Feb 12 22:14 usr
lrwxr-xr-x@   1 root  admin    11B Feb 12 22:14 var -&gt; private/var


So I can see there is an incorrect group in the alias /tmp directory, but correct in /private:

$ ls -lah /private/
total 0
drwxr-xr-x    6 root  wheel   192B Feb 13 01:22 .
drwxr-xr-x   22 root  admin   704B Feb 12 22:16 ..
drwxr-xr-x  126 root  wheel   3.9K Mar 30 00:07 etc
drwxr-xr-x@   2 root  wheel    64B Feb 13 01:22 tftpboot
lrwxr-xr-x@   1 root  wheel    11B Jun 27  2018 tmp -&gt; private/tmp
drwxr-xr-x   31 root  wheel   992B Feb 13 08:08 var


So the next step is try to set the correct group on /tmp, but, since Catalina, the System partition is read-only:

$ sudo chown root:wheel /tmp 
Password:
chown: /tmp: Read-only file system


Obliviously I've already disabled SIP:

$ /usr/bin/csrutil status
System Integrity Protection status: disabled.


So, whats next? Got any suggestion?
I see exactly the same group ownership on my Catalina system, so I suggest that this isn't the cause of whatever problems you have.

Perhaps ask another question detailing the problems with installing applications and writing to /tmp ?