Copying here a question I asked on StackOverflow:
https://stackoverflow.com/questions/58846076
=======================================
On my system, `/home` and `/etc` have exactly the same permissions:
```
$ ls -ld /home /etc
drwxr-xr-x 67 root root 4096 Nov 13 15:59 /etc
drwxr-xr-x 3 root root 4096 Oct 18 13:45 /home
```
However, Postgres can read one, but not the other:
```
test=# select count(*) from (select pg_ls_dir('/etc')) a;
count
-------
149
(1 row)
test=# select count(*) from (select pg_ls_dir('/home')) a;
ERROR: could not open directory "/home": Permission denied
```
Even though the user the DB is running as can, in fact, run `ls /home`:
```
$ sudo -u postgres ls /home > /dev/null && echo "ls succeeded"
ls succeeded
```
What is going on?
My postgres version is 11.5, running on Arch Linux.
