Lecture 18CS311 – Operating Systems 1 1 CS311 – Lecture 18 Outline Midterm 2 Review Note: These lecture notes are not intended replace your notes. This is what I expect your notes to already look like, but with more explanation as needed. 1

Lecture 18CS311 – Operating Systems 1 2 Midterm 2 study guide You will be reading / writing code with any of the following system calls (review fileIO.c on the Schedule page or your Project 3 code): – open: know when to use or not use O_CREAT, O_CREAT|O_EXCL; know that you HAVE to use exactly one of O_RDWR, O_RDONLY, O_WRONLY – close – lseek – read (you could be asked to deal with structs, ints, chars, strings,...) – write (you could be asked to deal with structs, ints, chars, strings,...) 2

Lecture 18CS311 – Operating Systems 1 3 Midterm 2 study guide Be able to use the open system call to create a lockfile to keep other processes out of a critical section. Be able to write code that calls perror if any of the above calls fails. 3

Lecture 18CS311 – Operating Systems 1 4 Midterm 2 study guide What information is contained in an i-node? What information is NOT contained in an i-node? – What do the r, w, x permissions let you do to a regular file? – What do the r, w, x permissions let you do to a directory file? Given block size and inode structure, w hat is the size of the largest file that can be stored in this File System? 4

Lecture 18CS311 – Operating Systems 1 5 Midterm 2 study guide What is the detailed explanation of how a file system finds the file readMe.txt from the following absolute path? /nfs/dirA/readMe.txt If I give you a sequence of commands (cp, mv, ln, ln with -s option, rm, echo "hi" > aFile,...) – Can you draw what the directory's data block looks like? What the inodes look like? What the other file's data blocks look like? 5

Lecture 18CS311 – Operating Systems 1 6 Midterm 2 study guide Given a makefile, you should be able to write what appears on the screen after commands such as: make abc make touch something.c make 6

Lecture 18CS311 – Operating Systems 1 7 Midterm 2 study guide Organization of Unix Process state diagram Process image in virtual memory diagram Unix / Linux filesystem security via what 2 mechanisms? multprogramming and timesharing If we didn't have a multiprogramming OS what would be missing? – 1) Only one user at a time – 2) That one user could run only one process (application) at a time 7