Permissions – How to Give Debian-Transmission Write Access to www-data Directory

The last command in that set:

sudo chown your_user -R /etc/transmission-daemon/settings.json 

sets your user as the owner of the settings file, and that file has read-permissions only for the owner by default. Transmission won't even be able to read it. Try:

sudo service transmission-daemon stop 
chmod g+rw /etc/transmission-daemon/settings.json 
sudo service transmission-daemon start

Since the commands don't change the group ownership of that file, giving it group read/write permission should be enough to get Transmission to start.

There are other problems as well, so I suggest these modifications as well:

chmod g+rw /var/lib/transmission-daemon/info/
chmod u+s /your_path/progress /your_path/completed

This will:

1. Give the daemon the necessary write permissions on /var/lib/transmission-daemon/info/, where it stores the current status.
2. Ensure that files created in the download and temporary folders are owned by you, by making the folders setuid.

This guy Tom deserves a medal for this post on ServerFault

Setting group ID the way he explains made it work!

Attempting to expand on @Zoredache's answer, as I give this a go myself:

• Create a new group (www-pub) and add the users to that group

  groupadd www-pub 
  usermod -a -G www-pub usera    # must use -a to append to existing groups
  usermod -a -G www-pub userb
  groups usera    ## display groups for user
  

• Change the ownership of everything under /var/www to root:www-pub

  chown -R root:www-pub /var/www    # -R for recursive
  

• Change the permissions of all the folders to 2775

   chmod 2775 /var/www 
  

  2=set group id, 7=rwx for owner (root), 7=rwx for group (www-pub), 5=rx for world (including apache www-data user)

  Set group ID (SETGID) bit (2) causes the group (www-pub) to be copied to all new files/folders created in that folder. Other options are SETUID (4) to copy the user id, and STICKY (1) which I think lets only the owner delete files.

  There's a -R recursive option, but that won't discriminate between files and folders, so you have to use find, like so:

  find /var/www -type d -exec chmod 2775 {} +
  

• Change all the files to 0664

  find /var/www -type f -exec chmod 0664 {} +
  

• Change the umask for your users to 0002

  The umask controls the default file creation permissions, 0002 means files will have 664 and directories 775. Setting this (by editing the umask line at the bottom of /etc/profile in my case) means files created by one user will be writable by other users in the www-group without needing to chmod them.

Test all this by creating a file and directory and verifying the owner, group and permissions with ls -l.

Note: You'll need to logout/in for changes to your groups to take effect!