Lab 7a Managing fielsystesm Mounting Unmounting

On the host operating system of a Linux workstation in the Faculty labs, determine and document the structure of the filesystem. Include all of the currently mounted filesystems. How many hard disks are in the machine? Do they appear to be IDE or SCSI disks? How many partitions are there on the disk(s)? Identify which partitions are primary, extended and logical partitions. Which are logical volumes? Where are home directories stored? Where is the _/tmp directory stored?

Hints: Look at both _{/proc/partitions} and the fstab file. You can also look in /dev/disk/by-_uuid or use the /sbin/b_lkid command to figure out the mapping of UUIDs to partitions (blkid may require root privileges).

Repeat this process for your virtual machine OS. How many (virtual) hard disks? Can you tell from the device file names whether the disks are SATA, IDE or SCSI? How many partitions? This time use the _{fdisk –l} command to print the partition table as well as looking at _{/proc/partitions} and the fstab file. Which partitions are primary, extended and logical? Where are home directories stored? Where is the _/tmp directory stored? This time you can also refer to the previous lab on disk partitioning for other ways to view disk partitions (as opposed to mounted filesystems). Because this requires root privileges, you couldn’t do it on the host OS.

In an earlier lab exercise, you should have created four users named Peter, Stewie, Brian and Lois, and assigned two of those users, Stewie and Brian, to a group called family. This task builds on that earlier work. Let us assume that Stewie and Brian have the groups stewie and brian as their primary groups respectively (the default case under CentOS, Fedora and Red Hat Linux), but both are also members of the family group. That is, the family group is a secondary group for Stewie and Brian. If this is not the case, you might like to adjust group memberships to comply with the above. This makes the task more difficult, but more interesting.

Now assume that members of the family group need to share files with each other. Make a directory called /share/family. Make it so that Stewie and Brian (members of the family group) can read and create files in this directory, but Peter (who is not a member of the family group) cannot. Make sure that in this directory, files created by Stewie can be read and edited by Brian and vice versa (but they should not be world readable).

To solve this problem, you will need to use three things:

• UNIX file permissions on the _{/share/family} directory, including the SetGID bit (_chmod command)

• Group ownership of the /_share/family directory (_chgrp command)

• The _umask settings of Stewie and Brian, so that files are created group writable by default (_umask command, e.g. in

their .bashrc file)

In your virtual machine, change the _/tmp directory from being part of the root filesystem to using a _tmpfs filesystem. First, create an empty file in the _/tmp directory (e.g. "_{touch /tmp/mytest}"). Then make the necessary change to the

/etc/fstab file so that /tmp uses tmpfs, as follows:

tmpfs /tmp tmpfs defaults 0 0

Then mount the filesystem with ‘_{mount /tmp}’. Use the _mount command again (with no arguments) to show currently

mounted filesystems and verify that _/tmp is now using _tmpfs. Also verify that the file you created earlier

(_/tmp/mytest) is not there any more in the _tmpfs filesystem (where is it?).

After doing this, you might want to change _/tmp back to the way it was before, so as not to degrade the performance of your virtual machine by using _tmpfs (since your VM does not use very much memory in total).