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I'm redoing my Linux systems at home, and am wondering about partition sizes. In the past, I've always installed Linux on a single partition; I'd like to setup the system as follows:

  • /
  • /boot
  • swap
  • /home

I'm not 100% certain how much space should be devoted to the '/' partition. Swap will be 2x RAM; boot will be ~200M. How much should the OS receive? I was thinking of giving it between 15 and 20G (and all else to /home where most of my files will be located), but I wasn't sure if it would need more.

Is there a standard way of determining the partition size for '/'?

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Not that it matters much these days, but you really don't need 200M for a /boot partition. I've never gone over 50M myself. –  Richard Marquez Sep 20 '09 at 16:41
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7 Answers

up vote 7 down vote accepted

I think 10 GB is plenty.

I am running a Ubuntu server within 10GB (including /home) and it is puffing along fine. Excluding my files, the system takes up less than 4GB. If you ever find yourself pressed for space, you can always resize the partitions at a later date.

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Ditto, I managed to hit the 5GB limit on my / partiton, but I was able to move my swap partition which was after it, and expand it to 13GB. I'm now at 6GB used on /. –  Macha Sep 20 '09 at 17:09
    
Reading these answers carefully, it sounds like both of you advocate combining at least / and /home on a single partition rather than separating them. I agree but would go further and use one / partition for the whole drive with no swap. The /boot would then be on the / partition and if you need swap, you would use swapfiles on the / partition. –  Michael Dillon Nov 4 '09 at 10:56
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Use LVM and a filesystem that supports online resizing (includes ext3/4 with the right mkfs options, which should be the default) and then you can easily grow it if needed.

I'd start with 2–4G on a server, maybe 5G on a desktop, because growing it is trivial with LVM.

Or, alternatively, there really isn't anything wrong with everything on / for a desktop.

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+1 for LVM... but -1 for the last point. I find that having /home on a separate partition has positive consequences, even on a desktop (if you reinstall your system, if you run several distros, if you have several disks, etc). –  Pascal Thivent Sep 20 '09 at 23:05
    
@Pascal: I get the point about reinstalls (though doing reinstalls w/o touching /home is fairly easy at least with the distro I use), but surely using multiple distros is going to be a different question; after all, you'd probably have partitions for each (and have to deal with uid/gid sync, etc.) Oh, and mount --bind helps with that, too. –  derobert Sep 22 '09 at 6:45
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It highly depends upon the Linux distribution you are going to install,

Because DSL(Damn Small Linux) or Puppy Linux are mere 60 -70 'MB' whereas Fedora goes in 4-5 GB and Ubuntu in 2-3 GB

It even depends upon how much you are going to use Linux, i.e the softwares you are going to install

For Latest Fedora releases 10 GB is enough.

For ubuntu use 5 GB

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Depends on how are you going to use /tmp, as it resides in /. Building a DVD may take a lot of space there

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Swap will be 2x RAM;

This is actually a very old sizing rule and I think it's obsolete. On modern systems (i.e. with 1GB or more of RAM), I give 1x RAM for Swap.

boot will be ~200M.

Wow! How much kernels do you plan to use, 20? For most users, 50Mo is enough.

How much should the OS receive? I was thinking of giving it between 15 and 20G (and all else to /home where most of my files will be located), but I wasn't sure if it would need more.

Is there a standard way of determining the partition size for '/'?

I don't know a "standard" way as it highly depends on how much software you'll install and what you'll be doing with your computer. A server install (mail, database...) will typically use a pretty big separated /var partition. For a personal machine, this is most of time useless. In fact, 10 GB for / should be more than enough for most users. If you plan to install many (and I really mean many) packages, you might need some additional GB, but not more than 15 GB. If you plan to install external softwares (e.g. in /opt), take it into account (I personally have many Java stuff installed in /opt, like commercial app servers that are not really lightweight). If you are going to rip DVDs, add a few more gigs. And indeed, use the rest of the space for /home.

Actually, you should now understand why it's hard to give an absolute answer and experience (i.e. trial error) is the best way to find the "perfect" sizing for your machine. But even for an experienced user, needs might change with time. That's why, as someone pointed out, LVM and resizable filesystems are weapons of choice to avoid any pitfalls.

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Keep in mind that the biggest folders in your file system are (on a debian system, but its a good guideline):

  • /usr: all user programs (/usr/bin), libraries (/usr/lib), documentation (/usr/share/doc), etc., are in this directory. This part of the file system needs most of the space. You should provide at least 500 MB of disk space. If you want to install more packages you should increase the amount of space you give this directory.

  • /home: every user will put his data into a subdirectory of this directory. The size of this depends on how many users will be using the system and what files are to be stored in their directories. Depending on your planned usage you should reserve about 100 MB for each user, but adapt this value to your needs.

  • /var: all variable data like news articles, e-mails, web sites, APT's cache, etc. will be placed under this directory. The size of this directory depends greatly on the usage of your computer, but for most people will be dictated by the package management tool's overhead. If you are going to do a full installation of just about everything Debian has to offer, all in one session, setting aside 2 or 3 gigabytes of space for /var should be sufficient. If you are going to install in pieces (that is to say, install services and utilities, followed by text stuff, then X, ...), you can get away with 300 - 500 megabytes of in /var. If hard drive space is at a premium and you don't plan on using APT, at least not for major updates, you can get by with as little as 30 or 40 megabytes in /var.

As you will have a different /home partition, you could go with as little as 4GB (plus /home, /var (50MB), /boot (100MB) and swap (300MB-2GB)), with a fully working system.

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For a standard desktop or laptop installation, there is little advantage in separating your partitions. If you know how to use LVM, that's the best solution, but there's nothing wrong with just having one big partition (and a second one for swap).

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