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Permissions

chmod, suid and umask

QuestionAnswer
The portion of a file's inode that stores permissions is known as the: mode
To change permissions for a specified file chmod
chmod Options: Add a permission for a user, group, or other (category) to a file category+permission
category+permission Example: Add execute permission to the myfile for user, group, and other chmod u+x,g+x,o+x myfile
Category-permission Example: Remove the write permission for group and others for the myfile file chmod g-w,o-w myfile
Category=permission Example: Grant the user read, write, and execute permission for the file myfile chmod u=rwx myfile
Chmod Options: Set the permissions of a file according to the numbers represented for each category chmod decimal_value
Decimal_value Example: Grant the user read, write, and execute permission, Grant the group read and execute permissions, and others just execute permission for the myfile file chmod 751 myfile
Sets the permission(s) recursively chmod -R
If -- -- is set, program will run with the permissions of the USER SUID bit
When issuing the ls -l command, SUID bit will show an -- in the --permission position of the USER permissions An s in the execute position of the user: rwsrw-rw-
If -- -- is set, program will run with the permissions of the GROUP SGID bit
When issuing the ls -l command, SGID bit will show an -- in the --permission position of the GROUP permissions An s in the execute position of the group: rwxrwsrw-
When issuing the ls -l command, Sticky bit bit will show an -- in the --permission position of the OTHER permissions A t in the execute position of the OTHER Permission: rwxrw-rwt
Mark a file in such a way as to prevent the file's DELETION from anyone except the file owner (works well with shared files) Sticky bit - (does not work with directories)
Chmod Options when assigning Special Permissions: decimal_value The permission precedes the standard octal representation of a set of permissions
chmod decimal_value: Value precedes the standard octal representation of a set of permissions - Set the SUID chmod (4)421
chmod decimal_value: Value precedes the standard octal representation of a set of permissions - Set the SGID chmod (2)421
chmod decimal_value: Value precedes the standard octal representation of a set of permissions - Set the Sticky bit chmod (1)421
chmod decimal_value: Value precedes the standard octal representation of a set of permissions - Set both the SUID and the SGID chmod (6)421
chmod category+permission - adds a special permission for a user, group, or other (category) of a file - Set the SUID chmod u+s
chmod category+permission - adds a special permission for a user, group, or other (category) of a file - Set the SGID chmod g+S
chmod category+permission - adds a special permission for a user, group, or other (category) of a file - Set the Sticky bit chmod u+t
chmod category-permission - Removes a special permission for a user, group, or other from a file - Remove the SUID chmod u-s
chmod category-permission - Removes a special permission for a user, group, or other from a file - Remove the SGID chmod g-s
chmod category-permission - Removes a special permission for a user, group, or other from a file - Remove the S chmod u-t
chmod decimal_value: Value precedes the standard octal representation of a set of permissions - Set the SUID, SGID, and Sticky bit chmod (7)421
Changes (removes) the default file and directory permissions umask
By default files receive permissions of: rw-rw-rw (666)
By default Directories receive permissions of: rwxrwxrwx (777)
Identifies which permissions are REMOVED from the DEFAULT permissions when files (666) and directories (777) are created umask
Is the typical umask setting 022
A umask of 022 results in a newly created file (default 666) permissions of 644 (666 minus 022 = 644) - (rw-rw-rw- minus ----w--w- = rw-r--r--)
A umask of 022 results in a newly created Directory (default 777) permissions of 755 (777 minus 022 = 755) - rwxrwxrwx minus ----w--w- = rwxr-xr-x)
Command to set a typical umask value umask 022
view the current umask setting umask
Created by: johnadream
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