python Popen chmod error starting Postgresql

Question

I can run:

sudo service postgresql start

from the command line with no issues. However when I try running the following:

import os
from subprocess import Popen,PIPE

pwd = getsudopwd()
cmd = ['sudo','service',process,'state']
p = Popen(cmd,stdout=PIPE,stdin=PIPE,stderr=PIPE,universal_newlines=True)
out,err = p.communicate(pwd+'\n')
if err: raise RuntimeError(err)

I get the following error

chmod: changing permissions of '/var/run/postgresql': Operation not permitted. So, why is there is an error accessing the pid directory for postgresql when this is run from Python?

I tried this on OSX and Trusty, and it worked fine. I couldn't supply password the way you want it, but you should be able to run echo "mypasswd" | sudo -S command. The -S option will force sudo to read passwd from the stdin. — Boris, Feb 21 '15 at 23:39
He should be able to create another process (for example, echo process) and set the stdin of the sudo process to echo.stdout. — Boris, Feb 21 '15 at 23:48
related: [Using sudo with Python script](http://stackoverflow.com/a/24257940/4279) — jfs, Feb 22 '15 at 01:42

Padraic Cunningham · Accepted Answer · 2015-02-22T01:44:46.703

2

You can simply use -S with sudo:

from subprocess import Popen, PIPE
import getpass

pwd = getpass.getpass()
proc = Popen(['sudo', '-S', 'service',process,'state'],
             stdout=PIPE, stdin=PIPE, stderr=PIPE,universal_newlines=True)
out,err= proc.communicate(input="{}\n".format(pwd))

edited Feb 22 '15 at 01:44

answered Feb 22 '15 at 00:18

Padraic Cunningham

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you should leave `stdout`, `stderr` separate: `stderr=PIPE` as in the question (`sudo` writes the prompt to stderr with the `--stdin` option, the child process might right to stdout something useful). – jfs Feb 22 '15 at 01:38

score 0 · Answer 2 · answered Feb 21 '15 at 23:59

0

i suggest you use the sh library

its very simple and easy to use

from sh import sudo
print sudo('service postgresql start')

answered Feb 21 '15 at 23:59

Urban48

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how does it help to pass the sudo password available in `pwd` variable? – jfs Feb 22 '15 at 01:40

score 0 · Answer 3 · answered Feb 22 '15 at 00:04

Running sudo command with the -S option and piping your password to the stdin of the sudo command should solve your problem.

import os
from subprocess import Popen, PIPE

echo = Popen(('echo', 'mypasswd'), stdout = PIPE)
p = Popen(['sudo', '-S', 'service', 'postgresql', 'restart'], stdin = echo.stdout, stdout = PIPE, stderr = PIPE, universal_newlines = True)
out, err = p.communicate()
print out

python Popen chmod error starting Postgresql

3 Answers3