Secure installation of Debian using Logical Volume Manager

Question

I am installing Debian for the very first time and having read websites similar to http://www.virasec.be/content/how-install-secure-debian-gnulinux-server I have come across parts of the installation which I do not understand.

For example, I have created logical volumes using the logical volume manager however am unclear what the message regarding writing changes to disk before configuring Logical Volume Manager means.

Once I have created the volume group, I am presented with a window that provides me with the ability to

1. Display configuration details
2. Create volume groups
3. Create logical volume
4. Delete logical volume
5. Extend volume group

Option 2 is pretty self-explanatory however am unsure whether it is advisable to segment directories between 2 or more volume groups. What benefits does it serve?

Option 5 provides me to extend a volume group however am unsure how this works? Does it mean I can assign free space available one 1 physical drive to the existing volume group or does it mean I can assign free space available on a second phyical drive or does it mean both? How does it affect security, performance, etc?

Currently the only way I can see the logical volumes I have created by selection Option 4. Is there any other way? How do most people keep track of the logical volumes they have created e.g. checking off against a checklist, etc?

Next I have the ability to map the logical volumes to mount points however am confused what purpose the none mount point serves as I have the option to select it?

What are mount options for?

What do I use labels for?

What are reserved blocks for?

What does typical usage refer to?

How does the option to copy data from another partition work? What is it for?

Answer 1

however am unclear what the message regarding writing changes to disk before configuring Logical Volume Manager means.

It is a standard 'are you sure prompt' telling you that you are going to make change to the partitions, and if you did something wrong, then you are about to destroy data. If you don't have a backup, and you don't know what you are doing, this is your chance to stop before you actually wreck something.

What are mount options for?

The sets features of the filesystem. You might want to enable quotes, or disable tracking of access times, mount as read only. The options available depend on the filesystem. See man mount or man mount.{filesystem} where {filesystem} is the filesystem you are using for the list of options.

What do I use labels for?

The allow you to give a human readable name to the filesystem. It probably isn't needed for LVM since the logical volume already has a name. But labels can be applied to filesystems that live on standard MBR partitions as well. If you have lots of portable drives, adding labels can be very useful to provide you a way in software to tell them apart.

What are reserved blocks for?

Setting aside space so that only root can use it. This helps the system run, having some spare space means that Linux can avoid fragmentation, and it prevents your system from crashing of a user tries to upload more stuff onto the drive then you have capacity for. Leave it at the default.

What does typical usage refer to?

This helps the install figure out what the block size should be. By default it will be 4k, but if you happened to be running a NNTP server, or an SMPT server, using maildir, then you will almost certainly have hundreds of thousands of small files. A larger block size means you would waste a huge amount of space. For a desktop system leave it at the default.

Option 2 is pretty self-explanatory however am unsure whether it is advisable to segment directories between 2 or more volume groups. What benefits does it serve? ... Option 5 provides me to extend a volume group however am unsure how this works?

For a desktop system you almost certainly want a single volume group. There probably isn't much reason to have more.

LVM has some advanced RAID-like features for spanning, striping, and duplicating data. The expand option would all you to add more physical devices to an existing LVM to provide you more capacity so that you could grow the logical volumes, or add additional volumes.

If you haven't read it yet, please see the LVM HOWTO. It covers a lot of details about LVM.

If I leave the typical usage to 4K, I assume that each file would consume 4k of space even when it is not needed. Is that correct? What is the smallest size I can have?

Yes, a 1 byte file will use up the space of a full block (depending on the filesystem). The allowed block sizes also are different based on what filesystem you are using. EXT3 supports block sizes of 1024, 2048 and 4096 bytes normally.