Cannot read from /tmp with PostgreSQL COPY, but able to read the same file from another directory with the exact same permissions I have a file /tmp/foo.csv that looks like this:

1,2
10,20
100,200


I have the same exact file in another directory /mydata/foo.csv. Both directories and files have the same exact permissions, owner, and were created by the same user, yet when I run

COPY foo FROM '/tmp/foo.csv' (FORMAT CSV, DELIMITER ',', HEADER TRUE);


I get this error

ERROR:  could not open file "/tmp/foo.csv" for reading: No such file or directory


When I run

COPY foo FROM '/mydata/foo.csv' (FORMAT CSV, DELIMITER ',', HEADER TRUE);


I see COPY 3.

What am I missing here?

Here's the relevant file and directory information:

╭─foo@bar  / ‹py27› 
╰─$ ll -d /mydata /mydata/foo.csv /tmp /tmp/foo.csv                                                                                                                       1 ↵
drwxrwxrwt  2 root root 4.0K Sep  9 08:26  /mydata
drwxrwxrwt 17 root root  420 Sep  9 08:57  /tmp
-rw-r--r--  1 root root   17 Sep  6 12:03  /mydata/foo.csv
-rw-r--r--  1 root root   17 Sep  9 08:36  /tmp/foo.csv
╭─foo@bar  / ‹py27› 
╰─$ diff /mydata/foo.csv /tmp/foo.csv
╭─foo@bar  / ‹py27› 
╰─$ 


I'm running Arch Linux

NOTE: I've also tried this on another Linux machine running CentOS and I was unable to reproduce the problem.
On Arch, the systemd script for PostgreSQL (/usr/lib/systemd/system/postgresql.service) enables private /tmp, which means the PostgreSQL server process can't communicate with the user using /tmp. 

Two possible solutions:


Create a new folder somewhere else and give user postgres read privileges on it: # sudo mount -t tmpfs -o users,rw tmpfs /data
(NOT RECOMMENDED) Set PrivateTmp option in postgresql.service to false.