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Resolving permissions problems

This How-To is about finding and resolving permission issues where PMS cannot read the file(s) due to a problem somewhere in the path.

While the process is straight forward (perform ls -la for each directory in the pathname to the file), the process is time consuming and somewhat tedious.

This HowTo provides a basic script which you can use (change from read-test to write-test if needed) and find where user plex loses its permission to get to a specific file.

Consider the case of file: /tmp/a/b/c/d/e.mp4

The process

Step 1 - Temporarily make user plex a viable shell user account

Step 2 - Copy the text below to a file (making it a script)

I’ve named this “can-read”

#!/bin/sh

if [ "$1" = "" ]; then
  echo usage: $0 path-to-check
  exit 1
fi

Dir="$1"
while [ "$Dir" != "" ]
do
  if [ -r "$Dir" ];  then
    echo READ: \"$Dir\"
  else
    echo FAIL: \"$Dir\"
  fi

  NewDir="$(dirname "$Dir")"
  if [ "$NewDir" = "$Dir" ]; then
    Dir=""
  else
    Dir="$NewDir"
  fi
done

Copy the script and change the -r test to -w to test for write access

Step 3

After making it executable, start testing pathnames with :

su -s /bin/sh plex   can-read  /path/to/file.ext

Example

Check read permissions for `/tmp/a/b/c/d/e.mp4

# su -s /bin/sh plex ./can-read /tmp/a/b/c/d/e.mp4
FAIL: "/tmp/a/b/c/d/e.mp4"
FAIL: "/tmp/a/b/c/d"
FAIL: "/tmp/a/b/c"
READ: "/tmp/a/b"
READ: "/tmp/a"
READ: "/tmp"
READ: "/"
#

Notice the fail point?

Checking permissions using ls -la finds the permissions problem.

# cd /tmp/a/b
# ls -la
total 0
drwxr-xr-x. 3 chuck chuck 60 Mar 28 03:13 ./
drwxr-xr-x. 3 chuck chuck 60 Mar 28 03:13 ../
drwx------. 3 chuck chuck 60 Mar 28 03:13 c/
#

Step 4 - Fixing the problem

We observe that, at /tmp/a/b , directory c does not permit anyone except the owner to access it.

We correct this by fixing the permissions chmod 755 /tmp/a/b/c

One last verification confirms everything is now correct.

# su -s /bin/sh plex ./can-read /tmp/a/b/c/d/e.mp4
READ: "/tmp/a/b/c/d/e.mp4"
READ: "/tmp/a/b/c/d"
READ: "/tmp/a/b/c"
READ: "/tmp/a/b"
READ: "/tmp/a"
READ: "/tmp"
READ: "/"
#

User plex will now be able to access everything from c down.

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