2

I want to (soft)link my .thunderbird dir onto the actual directory which is on a SD card.

Thus,

(xenial)florian@localhost:~$ ls -la /var/host/media/removable/SD\ Card/.thunderbird/
total 24
drwx------.  5 florian florian 4096 May 21 09:23 .
drwxrwxrwx. 10 florian florian 4096 Mar  4 22:42 ..
drwx------.  3 florian florian 4096 Apr  6 13:43 Crash Reports
drwx------. 10 florian florian 4096 May  7 20:39 kps6nx9x.default
drwx------.  2 florian florian 4096 Nov  8  2018 Pending Pings
-rw-rw-r--.  1 florian florian   94 Nov 14  2013 profiles.ini
(xenial)florian@localhost:~$ ls -la .thunderbird 
lrwxrwxrwx. 1 florian florian 47 May 21 09:32 .thunderbird -> /var/host/media/removable/SD Card/.thunderbird/

I changed permissions all the way down to /var/host/media/removable/SD Card:

drwxrwxrwx.  15 root root  4096 Sep 15  2018 var
drwxrwxrwx.  9 root root     4096 Sep 15  2018 host
drwxrwxrwt. 5 root    root     100 May 20 21:22 media
drwxrwxrwx. 10 florian florian 4096 Mar  4 22:42 SD Card

Still, however,

(xenial)florian@localhost:~$ ls .thunderbird 
ls: cannot access '.thunderbird': Permission denied

What is going on here?

  • Do you have a file /proc/sys/fs/protected_symlinks ? If so, is cat /proc/sys/fs/protected_symlinks 0 or 1 ? – Mark Plotnick May 21 at 8:41
  • The file exists and cat /proc/sys/fs/protected_symlinks is 1. – Florian Theilmann May 21 at 9:05
  • What filesystem is on the SD card? If FAT32 or NTFS, you will need to make sure it's mounted with dmask/fmask set (in case of vfat) or uid=1000 (in case of ntfs). See here for an example of vfat: unix.stackexchange.com/a/37074/111122 – Egon May 21 at 18:37
3

Run sudo chmod o-t /var/host/media.

Reference: https://sysctl-explorer.net/fs/protected_symlinks/

This is the problem with your permissions:

drwxrwxrwt. 5 root    root     100 May 20 21:22 media

The t at the end of this means that the directory is sticky.

Quoting from the linked webpage:

When set to "1" symlinks are permitted to be followed only when outside a sticky world-writable directory, or when the uid of the symlink and follower match, or when the directory owner matches the symlink's owner.


Another thing, just pointing out something that you don't want to do here:

I changed permissions all the way down to /var/host/media/removable/SD Card:

Not a good idea. Now everybody will be able to read, write, and execute all the files you have under /var. Better to change them back to what they were before (i.e. restore a backup or in dire cases reinstall).

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