Answer:
See explanation.
Step-by-step explanation:
(a)
• To grant read access to a file for all users, access control list (ACL) is the best option.
o Create a group called 'all' with all users in it (assume the group name as 'all').
o Make a ACL for the file name with ACL as 'all:R'.
• It can also be done with capability list. With capability lists. it is sufficient to place the capability for the file in appropriate place in a capability system.
(b)
• To revoke write access for a file from all users, access control list (ACL) is the best option.
o Edit the ACL by removing the write access.
o If the group 'all: W' was the entry added to ACL, remove it from the ACL.
• It can also be done with capability list by changing the check field stored with the object.
(c)
• To grant write access to a file to John, Lisa. Christie and Jeff either the access control list method or the capability list can be used.
• It can be implemented with ACL as follows:
o Construct ACL for the file for all users,
o Then the ACL for file would be 'Christie, Jeff. John, Lisa: W'.
• It can be implemented using capability list method as follows:
o First construct the capability list for the file, 'file:W'.
o Then assign the above capability for each user named John, Lisa, Christie and Jeff.
(d)
• To revoke execute access for a file from Jana, Mike, Molly, and Shane, access control lists are the only possibility.
o Edit the ACL by removing the execute access.
Hope this hels!