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I want to create a shared directory when a number of users (all belong to say mygroup) can create and edit files. I would like all files in this directory and subdirectory to belong to mygroup

I have changed existing files to have group mygroup using chgrp, but new files still get created belong to the user's primary group. Is there a way of ensuring new files belong to the group without repeatedly running chgrp.

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up vote 36 down vote accepted

You want to set the SetGID sticky bit.

chmod g+s dir

All new files created in the directory will have the group set to the group of the directory.

A superuser blog post explained the sticky bits and other linux permission bits:

SetGID, however, is a whole different ball game. When a directory has the SetGID bit set and a file is created within that directory the group ownership of the file is automatically modified to be the group of the directory.

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Thanks. The reference is useful. describes the umask command that is part of the picture – justintime May 2 '11 at 17:43
What about creating a subdirectory in the initial directory which also belongs to the group of the parent directory? Is this possible? – daaxix Mar 11 '13 at 22:27

Set the setgid permission flag on the folders.

chmod g+s dirname
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