COMP3000 Operating Systems W22: Tutorial 5

In this tutorial you will be learning about files and filesystems by experimenting with and extending 3000test.c, and creating and manipulating local filesystems. WARNING: Several of the commands here can lead to system corruption and data loss if not properly used. You have been warned. Please use a VM and make backups, when necessary.

Tutorials are graded based on participation and effort (so no need to try to have the “correct” answers — what matters is the process), but you should still turn in your work. Even if you have no idea about certain tasks or disagree about something, still make sure to document your confusions/opinions that reflect your thinking about that task. Submit your answers on Brightspace as a single text file named "<username>-comp3000-t5.txt" (where username is your MyCarletonOne username). The first four lines of this file should be "COMP 3000 Tutorial 5", your name, student number, and the date of submission.

The deadline is usually four days after the tutorial date (see the actual due date and time on the submission entry). Note that the submission entry is enforced by the system, so you may fail to get the effort marks even if it is one minute past the deadline.

You should also check in with your assigned TA online (by responding to the poll in the Teams channel tutorials-public or the private channel). Your TA will be your first point of contact when you have questions or encounter any issues during the tutorial session.

You get 1.5 marks for submitting answers that shows your effort and 0.5 for checking in, making this tutorial worth 2 points total.

Files and inodes

In UNIX/Linux filesystems, a filename does not directly refer to the contents of a file. Instead, a filename refers to an inode (as specified in a directory entry --- dentry, of its parent directory), and the inode then refers to the data. An inode is where file metadata is stored. File ownership, timestamps, and permissions are all stored in a file's inode. Regular files are just hard links connecting a file name to an inode. In addition to regular files, we also have symbolic links, directories, block devices, character devices, and pipes. Each is its own type of inode. Note that while you can find out a file's inode, you cannot go from an inode to a pathname or otherwise manipulate an inode directly from userspace - you always have to go through the pathname. The kernel, however, can access individual inodes directly (indeed it has to in order to get to the contents of a file when given a filename).

3000test.c uses stat() to give information on a given inode.