Arch Linux

redge

Member

Registered: 2006-12-20

Posts: 49

Why does the default install make a partition for boot?

The installer, if one lets it prepare one's hard drive, makes a partition for boot, and formats it as a second extended filesystem. I know that people debate the need for/desirability of a partition for boot, and I do not mean to revive that debate. Rather, I am interested in knowing why the Arch developers, like the developers of some other distributions, such as Gentoo, but unlike some, such as Slackware, call for a boot partition, with ext2fs file system, on a default install. Should Arch users interpret this as a recommendation? Also, why is the partition quite a bit larger (although tiny compared to the available space on hard drives these days) than seems necessary?

Thanks.

phrakture

Arch Overlord

From: behind you

Registered: 2003-10-29

Posts: 7,879

Website

Re: Why does the default install make a partition for boot?

It's a minor optimization.  In order to boot a given file (a kernel) that partition needs to be mounted.  You can run some tests.  Booting a small partition (100MB) is much faster than booting a large partition (100GB).  In addition, ext2 is a very basic file system.  It doesn't need to do a bunch of checking and such when mounted - reiser and ext3 may do some journal rebuilding and things of that nature.  Try mounting a 20GB reiser partition and compare that to a 20GB ext2 partition.

Basically, it's an optimization for speed.  There are other benefits as well (a seperate partition means it need only be mounted read-only, preventing you from corrupting it or overwriting kernels and things).

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http://phraktured.net

T-Dawg

Forum Fellow

From: Charlotte, NC

Registered: 2005-01-29

Posts: 2,736

Re: Why does the default install make a partition for boot?

I do it mostly for security as phrakture pointed out but its also conveinent to have a designated boot partition when using multiple linux installs. All boot related files can be managed in one location including boot configurations like grub.conf.

Also, because ext2 has no journal and thus little overhead compared to ext3 or reiserfs, its size can be small. 32M for an ext2 boot partition is plenty whereas if it were ext3 you would need that much just for the journal. Remember the  journal just speeds up checks -if you have fs errors they can still be restored just as well.

redge

Member

Registered: 2006-12-20

Posts: 49

Re: Why does the default install make a partition for boot?

I've looked at a couple of books and a fair number of internet posts on this, and I must say that these responses are a good deal more concise and clear than what I have come across. I did find it interesting that the Slackware on-line manual doesn't make any effort to encourage it. On the other hand, what you guys are saying sounds sensible enough.

I have both Arch and Gentoo running, sharing a boot partition, which I set at 50MB. I'm using 25% of it, which is why I ask about size - obviously not in terms of overall capacity, but in terms of need.

Why not a lot less - say, even if one is considering dual boot, 20MB? And where do numbers like 32MB come from (the Arch, and indeed Gentoo, default, also referred to by T-Dawg)? Why not use round numbers?

Does 32MB have some rational/irrational/astrological/lucky 7 connection to 64MB RAM, sort of like designating 128MB as swap instead of using numbers like 120MB or 125MB or 130MB?

As you probably know, in Gentoo this stuff is done on the command line in fdisk, and I found it quite odd to be told in their manual to tell fdisk that the boot partition should be 32MB (assuming a single operating system) and swap should be 256MB, especially since fdisk and my hard drive took these numbers with a grain of salt and conspired to adjust them to slightly different numbers complete with decimals. Arch, on default, does the same.

Then I find out that with two operating systems, I'm using about 13MB out of 50MB (or rather 49.9MB, as fdisk and my hard drive decreed)

To change the subject a bit, I think that it is a good idea that the current version of Arch .08 would create, on the default track, a /home partition. There are some nice ideas in the install dialogue, including in the section on setting up a hard drive.