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File Permissions Management

File permissions for Unix files can be managed from the Web.

Unix File Permissions

A Unix file or folder has a single individual owner plus a single group owner.

Current permissions of the individual owner are displayed and can be modified by

  • Adding checked permissions to current set
  • Removing checked permissions from the current set
  • Replacing the current set with a new set

Permissions for Unix file system files can be managed at https://ubfs.buffalo.edu/.

Using Groups

Groups are uniquely named entities for a particular system that can be used to specify file permissions. For example, at UB, there are institutional and AD groups.

Every user may be a member of one or more “groups”, including a “primary group”. Every file belongs to only one user and to only one group.

When a file is created in Unix, its owner is the person who created it. The default group is the primary group of the owner or the group of the directory in which it was created. Changing the group owner of a directory causes all files subsequently created in that directory to be created with the new group.

Finding Group Information

Log in to ubunix.buffalo.edu:

  • Type groups to see groups to which you belong.
  • Type grep group_name  /etc/group to display the membership of a particular group.

Changing Inherited File Permissions

Checking Apply Recursively causes a change (add, replace or remove) made to any folder to be made to all existing and future files or subfolders in that folder. To change permissions that have been inherited for a specific file or folder, use the replace or remove option to change the undesired permissions and then set the permissions on the target folder or file.

Setting Special Permissions

setuid and setgid

setuid (set user ID) and setgid (set group ID) are flags in Unix file systems that:

  • allow users to execute a file temporarily using the permissions of the file’s owner  (individual or group)
  • are represented symbolically by an s as in drwxrwxrws or drwxrwxrwS

Using setgid on a directory causes new files and subdirectories to inherit the specified group or the setgid bit

Using setgid on a directory does not affect existing files and subdirectories.

sticky bit

Sticky bit is a flag for directories in Unix file systems that:

  • disallows renaming or renaming files in the directory by anyone other than the file or directory owner or a superuser
  • is represented symbolically by a t in the final character-place, as in drwxrwxrwxt  or drwxrwxrwT

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