Operating Systems 2015F: Assignment 5

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1. Within a UNIX filesystem, one inode can be referred to by many different pathnames (filenames). What is another term for these names?
   • hard links
   • symbolic links
   • URLs
   • all of the above
2. A modern monolithic operating system kernel typically implements
   • scheduling \& address space management
   • some device drivers
   • a TCP/IP stack
   • All of the above
3. An OS that is based upon a microkernel

architecture will typically:

1. • have most device drivers and filesystem code run within separate userspace processes
   • have most OS code run in CPU supervisor mode
   • support loadable kernel modules
   • All of the above
2. A typical executing application is best

described as a:

1. • kernel
   • process
   • thread
   • system call
2. When a running program X requests data from a file F whose contents are on disk, the OS will:
   • save X's current state
   • schedule a disk request for F's data blocks
   • load the state of another ready-to-run program Y (which may be X)
   • All of the above
3. When a regular process is running on a single-CPU system, all of the following are true except:
   • The kernel is running.
   • Disks can be writing data to memory.
   • The CPU will generate an exception (software interrupt) if certain addresses are accessed.
   • The CPU is in user mode.
4. Modern virtual memory systems:
   • Logically divide RAM into fixed-sized chunks
   • Store portions of processes on disk
   • Allocate a logical address space to each process that is distinct from the physical memory map
   • All of the above
5. The ``dirty bit in a page table entry

indicates that:

1. • A security violation has occurred
   • The corresponding page has been accessed.
   • The corresponding page has been modified.
   • The corresponding page is shared between multiple processes.
2. An inode contains all of the following except:
   • user ID
   • filename
   • time of last data modification
   • link count
3. When checking the consistency of a filesystem (e.g. after a loss of power), all of the following must be checked except:
   • inode reference counts
   • pointers to data blocks (in inodes or indirect blocks)
   • contents of data blocks of regular files
   • block free list

# If a system automatically boots into a defective kernel (e.g., one that crashes on startup), you can recover the system by:

1. • Select a different kernel in the bootloader
   • Perform a soft reboot of the system
   • Perform a hard reboot of the system
   • Press Alt-SysRq-R
2. Virtual memory is prohibitively expensive on a system that lacks a TLB because
   • Every memory access then requires a system call.
   • The page table has to be checked on every memory access
   • The process table has to be updated on every tick interval.
   • None of the above