Names point at records, records point at blocks

Computing · Computer Systems · ages 20-21

Name ______________________ Date ____________

What is a path name?
- A copy of a file kept elsewhere
- A secret code that locks a file
- A chain of names walking folder by folder to one file
What does a directory actually store?
- The bytes of every file inside it
- A table mapping names to records
- A backup copy of each file
A hard link is a second name pointing at the same record as the first name.
Circle one: True False
Writing a large file is slow, yet deleting it is instant. Why?
- Deleting compresses the blocks first
- Deleting skips the permission check
- Only the small record changes, not every block
You run chmod 600 myfile.txt. What can others do with the file?
- Nothing at all
- Read it but not change it
- Run it but not read it
In -rw-r--r--, what do the three letter groups after the dash mean?
- Owner, group, and everyone else, each with read, write and run slots
- Three copies of the file on three disks
- Past, present and future versions of the file
You need a second path to a file without duplicating its bytes. What should you make?
- A hard link, which adds a name for the same record
- A full copy with the copy command
- A new empty file with the same name
A friend says a directory holds the bytes of its files. What is the best correction?
- True, folders contain the bytes directly
- The directory holds a name table, and records point at the blocks
- The bytes live inside the path string itself

Answer key

For grown-ups. Fold this page away before handing over the rest.

A chain of names walking folder by folder to one file · A path spells out the walk from the top folder down to the exact file.
A table mapping names to records · A directory maps each name to its record, and the record points at the blocks.
True · Both names map to one record, so both reach the same blocks.
Only the small record changes, not every block · Writing touches every block, while deleting only updates the small record.
Nothing at all · The 600 setting gives the owner read and write, and clears the rest.
Owner, group, and everyone else, each with read, write and run slots · Each group holds read, write and run slots for one class of user.
A hard link, which adds a name for the same record · A copy makes a new record with fresh blocks, while a link reuses the record.
The directory holds a name table, and records point at the blocks · Folders map names to records, and only records point at block locations.