Обсуждение: Linux file permission for COPY TO SQL command
I try to use COPY TO command to copy results of a SELECT but I get this message:
ERROR: could not open file "a file" for writing: Permission denied
User, group and other are granted full permission to this file. What should I do more to get this working?
-- Pozdrawiam Krzysztof Jasieński
On Oct 28, 2025, at 9:39 AM, Krzysztof <kj@limes.com.pl> wrote:
I try to use COPY TO command to copy results of a SELECT but I get this message:
ERROR: could not open file "a file" for writing: Permission denied
User, group and other are granted full permission to this file. What should I do more to get this working?
-- Pozdrawiam Krzysztof Jasieński
Hello,
COPY TO stores the output into a file on the server rather than in your local where client is running.
Spaces in the file name are actually no issue:
$ psql -h 172.17.0.2 -U postgres -c "COPY (SELECT * FROM pg_class) TO '/var/tmp/pg_class. OUT x'"
Password for user postgres:
COPY 420
... but the output file is on the server - in this example inside a docker container
postgres@7680e256387f:~$ ls -ltr /var/tmp
total 208
...
-rw-r--r-- 1 postgres postgres 49291 Oct 29 16:08 'pg_class. OUT x'
Copying to client side can be done with \copy (<query or table>) to '<output file>';
BR/Pozdrawiam,
Roland
On Oct 28, 2025, at 9:39 AM, Krzysztof <kj@limes.com.pl> wrote:I try to use COPY TO command to copy results of a SELECT but I get this message:
ERROR: could not open file "a file" for writing: Permission denied
Is there really a space in the actual file name. That might get tricky. You’re suggesting the file already exists: is that true? Directory permissions?User, group and other are granted full permission to this file. What should I do more to get this working?
-- Pozdrawiam Krzysztof Jasieński
Actually server and client are installed on the same machine.
The file (real file) permissions are as follows:
-rwxrwxrwx+ 1 kaj kaj 2 Oct 27 22:36 fd/fdo.txt
The directory permissions are as follows:
drwxrwxrwx+ 4 kaj kaj 4096 Oct 27 22:36 fd
The SQL command which tries to write to the file is this:
copy (select key from xcg where add=false) to '/home/kaj/fd/fdo.txt';
Pozdrawiam Krzysztof Jasieński
Hello,
COPY TO stores the output into a file on the server rather than in your local where client is running.
Spaces in the file name are actually no issue:
$ psql -h 172.17.0.2 -U postgres -c "COPY (SELECT * FROM pg_class) TO '/var/tmp/pg_class. OUT x'"
Password for user postgres:
COPY 420... but the output file is on the server - in this example inside a docker container
postgres@7680e256387f:~$ ls -ltr /var/tmp
total 208
...
-rw-r--r-- 1 postgres postgres 49291 Oct 29 16:08 'pg_class. OUT x'
Copying to client side can be done with \copy (<query or table>) to '<output file>';
BR/Pozdrawiam,
Roland
On 10/29/25 01:03, Rob Sargent wrote:On Oct 28, 2025, at 9:39 AM, Krzysztof <kj@limes.com.pl> wrote:I try to use COPY TO command to copy results of a SELECT but I get this message:
ERROR: could not open file "a file" for writing: Permission denied
Is there really a space in the actual file name. That might get tricky. You’re suggesting the file already exists: is that true? Directory permissions?User, group and other are granted full permission to this file. What should I do more to get this working?
-- Pozdrawiam Krzysztof Jasieński
Krzysztof <kj@limes.com.pl> writes:
> Actually server and client are installed on the same machine.
> The file (real file) permissions are as follows:
> -rwxrwxrwx+ 1 kaj kaj 2 Oct 27 22:36 fd/fdo.txt
> The directory permissions are as follows:
> drwxrwxrwx+ 4 kaj kaj 4096 Oct 27 22:36 fd
> The SQL command which tries to write to the file is this:
> copy (select key from xcg where add=false) to '/home/kaj/fd/fdo.txt';
The /home and /home/kaj directories would also need to be
world-searchable for the server to be able to write there.
(Do not make them world-writable...)
Did you notice the HINT that goes with that error message?
HINT: COPY TO instructs the PostgreSQL server process to write a file. You may want a client-side facility such as
psql's\copy.
regards, tom lane
I think the best solution is to use the psql '\copy' that works the same way as server-side COPY or COPY TO. in addition, the output is always stored in the client machine regardless whetehr the server is in localhost, remote or inside a container. postgres=# \copy (SELECT * FROM pg_class) to /home/MYACCOUNT/Desktop/OUT COPY 420 postgres=# \! ls -ltr /home/MYACCOUNT/Desktop/OUT -rw-rw-r-- 1 MYACCOUNT MYACCOUNT 49291 Oct 29 22:06 /home/MYACCOUNT/Desktop/OUT On 10/29/25 21:55, Tom Lane wrote: > Krzysztof <kj@limes.com.pl> writes: >> Actually server and client are installed on the same machine. >> The file (real file) permissions are as follows: >> -rwxrwxrwx+ 1 kaj kaj 2 Oct 27 22:36 fd/fdo.txt >> The directory permissions are as follows: >> drwxrwxrwx+ 4 kaj kaj 4096 Oct 27 22:36 fd >> The SQL command which tries to write to the file is this: >> copy (select key from xcg where add=false) to '/home/kaj/fd/fdo.txt'; > The /home and /home/kaj directories would also need to be > world-searchable for the server to be able to write there. > (Do not make them world-writable...) > > Did you notice the HINT that goes with that error message? > > HINT: COPY TO instructs the PostgreSQL server process to write a file. You may want a client-side facility such as psql's\copy. > > regards, tom lane > >
That helped. Thanks. Pozdrawiam Krzysztof Jasieński On 10/29/25 8:55 PM, Tom Lane wrote: > The /home and /home/kaj directories would also need to be > world-searchable for the server to be able to write there. > (Do not make them world-writable...) > > Did you notice the HINT that goes with that error message? > > HINT: COPY TO instructs the PostgreSQL server process to write a file. You may want a client-side facility such as psql's\copy. > > regards, tom lane > >