Hard Drive Partitioning

1. We assume that the system has four 146 GB drives, that are configured into two logical drives using mirroring.
2. Always use Ext 3 filesystem for all partitions, do not use Reisner which is a dead project (Ext3 is still not a  default of Suse 11 SP 1)
3. Mark all partitions except swap with format option (unless this is a re-install)
4. Unless you know LVM really well never put your root partition on LVM. It complicates recovery. If the system is unbootable then after booting from a recovery disk you will find out that you LVM disks are not visible. For many sysadmin at this point cold goes down the spine.
5. Swap file is a special Linux filesystem used by virtual memory management. If you have sufficient memory this file is never used, so it make sense to put it at the beginning of the drive (along with the /home partition -- another little used partition in Unix) to workhorse partitions such as root (that can include /usr and opt), /tmp and /var  closer to the middle of the drive.
6. Unless you want to have /usr as read-only partition, in Suse it is not needed (nor makes much sense) to create separate partitions for /usr and /opt. They can be merged with root partition. That makes usage of disk space more efficient.  

   primary partitions:

   1. /boot
   2. swap. Swap should generally be allocated as the second partition on disk after /boot as it mostly unused. For small amount of RAM (less then 8GB) swap should be approximately 2x ram-size. For large amount of RAM swap can he half of RAM. For example in case of workstation with just 2GB  you need  4GB for swap.
   3. /home. Typically this is a little used partition that should approximately 8-16 GB just for private files of sysadmin and users.  In case you run out of space it can already be converted into LVM volume

   Extended partitions

   1. root (think twice before putting root partition under LVM). Can include /opt and /usr. Total can be 16GB or something like that for everything.
   2. LVM partitions
      1. /var   For a typical serve should be around 20-30GB. This partition contains logs so it you have a web server or other large logs producing program it should be big.
      2. /tmp. Should probably be 6-12 GB
      3. /srv
7. With Suse 11 SP 1 you probably should always use LVM at least for /var  /home and /srv as size requirements for those partitions can change: it looks like there is no difference in stability and LVM provides additional flexibility and ability to create snapshots.
8. If you use SAN for data and local harddrives just for storing OS using LVM does not make much sense as SAN provides necessary flexibility in resizing partitions. 

To optimize disk configuration put swap and home partitions before root partition. This way root partition will be closer to the middle of the disk.

Old News ;-)

Cool Solutions Install Linux Frequently, Without the Hassle

With RPM-based Linux distributions, version-to-version upgrades often don't work very well.  A fresh installation may be the better choice.  One may be reluctant to do this, because of the potential loss of data, preferences, configuration, and third-party applications.  Also, if you don't like the newly installed system, the thought of reinstalling the old system to switch back to it is not a pleasant thought either.

This document describes a means of reinstalling Linux frequently, while minimizing the effort needed to become productive on a new system.  It also allows you to instantly and effortlessly rollback to a previous Linux OS if you aren't happy with a newly installed system.  Some possible applications of these suggestions include trying a new Linux distribution, or staying up-to-date with the latest beta release of your favorite Linux distribution.

Table of Contents

1. Introduction

1.1. Assumptions

2. Partitioning

2.1. Swap

2.2. Root Partitions

2.3. Data Partition

2.4. Variations

2.5. Partition Table Summary

3. Installing The First Instance of Linux

3.1. Install Target

3.2. Bootloader Location

3.3. Mount the Data Partition

4. Fixing the Bootloader

4.1. Move Bootloader Files

4.2. Install GRUB in the Boot Sector of the Root Partition

4.3. Edit the Boot Menu

4.4. Booting the Linux OS

5. Home Directory Maintenance

5.1. Setup the Data Partition

5.2. Symlinking to the Data Partition

5.3. Using the Customized Home Directory

6. Installing More Linux Systems

6.1. Bootloader Location

6.2. Mounting the Data Partition

6.3. Creating the Symbolic Links

7. Practical Use

7.1. Beta Snapshots

8. Other Hints

 

8.1. Third-party Applications

8.2. Make the Most of Symbolic Links

9. Summary

1. Introduction

If a little extra care is taken when first installing Linux on a system, it can require far less maintenance over the lifetime of the system. This document presents suggestions for using partitions and symbolic links to your advantage to minimize the effort required to test-drive a new Linux distribution.

1.1. Assumptions

The rest of this document makes the following assumptions:

The system has a single hard disk: /dev/hda

Windows is installed on /dev/hda1

Your hard disk is sufficiently large, relative to your needs, that you can leave at least one 5 to 10 GB partition unused at any given time

You know how to install Linux, including repartitioning

If your system differs from this, you'll need to make appropriate adjustments to the examples that follow.  For example, if you do not have windows installed, the swap partition can be /dev/hda1 instead of /dev/hda2.  If you actually think you can find a use for the entirety of your modern, huge hard disk, this document is not for you.
 

2. Partitioning

2.1. Swap

Use /dev/hda2 for the Linux swap partition.  It is usually recommended to have a swap partition 2x the size of physical RAM.  So, if you have 1GB RAM, make a 2GB swap partition.

2.2. Root Partitions

You'll want at least two root partitions so you can install a new version of the distribution, a different distribution, or a new build (or example, the next beta) without losing the Linux system you currently use.  This way you can always instantly rollback to the previous system without loosing any data.  Depending on the size of your hard disk, you'll probably want to make these partitions 5 to 10 GB each. 

2.3. Data Partition

Create one more Linux partition consuming the remainder of the hard disk.  This is where data will be stored so that it will not be lost when the OS is reinstalled onto one or the root partitions, and so that multiple systems can share the same data.

2.4. Variations

You can have other partitions if you like.  Perhaps you want to have a separate partition for VMWare images.  This isn't really necessary though since everything can be lumped under the Data partition, and symbolic links can be used if you want things to appear to be somewhere else.  If you want to share data between Linux and Windows, you may need an extra FAT32 partition.  Linux can read from NTFS volumes, but not write to them (last time the author checked).  By having an extra FAT32 partition (drive D: on Windows), you can put data on this partition and access it from either Windows or Linux. 

Normaly i use a swap partition of twice the size of the ram memory.

Creating dynamic swap space

Posted by Steve on Thu 27 Sep 2007 at 06:32

Tags: dphys-swapfile, swap, utitilities

When a GNU/Linux machine runs out of physical memory it will start to use any configured swap-space. This is usually a sign of trouble as swap files and partitions are significantly slower to access than physical memory, however having some swap is generally better than having none at all. The size of swap allocated to files, or partitions, is usually chosen arbitrarily with many people adopting the "double the memory size" rule of thumb. Using a dynamic system can ease the maintainance of this size.

The relatively unknown dphys-swapfile package contains a simple script which will create and activate a swapfile at boottime which is sized appropriately for your system.

The advantage of this dynamic creation is that the swap will be resized automatically if you upgrade your memory and don't remember to do it.

Upon recent kernels there doesn't appear to be a significant penalty to using swap files as opposed to swap partitions. With this in mind I'd recommend files rather than partitions, to give yourself more flexibility.

To get started first remove any existing swap you have allocated. You can view any swap space which is in use by running:

skx@vain:~$ /sbin/swapon  -s
Filename                                Type            Size    Used    Priority
/dev/md1                                partition       2931768 557428  -1

Here we see that there is swap allocated to the physical raid volume /dev/md1. We can disable that by running:

root@vain:~# /sbin/swapoff /dev/md1

Once it is gone we can now install the package upon installation the system will create and activate then new swap:

root@vain:~# apt-get install dphys-swapfile
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following NEW packages will be installed
  dphys-swapfile
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 9572B of archives.
After unpacking 111kB of additional disk space will be used.
Get: 1 http://apt-cache sid/main dphys-swapfile 20061020-1 [9572B]
Fetched 9572B in 0s (60.5kB/s)       
Selecting previously deselected package dphys-swapfile.
(Reading database ... 116206 files and directories currently installed.)
Unpacking dphys-swapfile (from .../dphys-swapfile_20061020-1_all.deb) ...
Setting up dphys-swapfile (20061020-1) ...
Starting dphys-swapfile swapfile setup ...
computing size, want /var/swap=1876MByte, generating swapfile ... of 1876MBytes
done.

Now whenever you boot you'll have /var/swap created at a size of twice your amount of physical memory, automatically.

You can verify this yourself with the swapon command we demonstrated earlier:

skx@vain:~$ /sbin/swapon  -s
Filename                                Type            Size    Used    Priority
/var/swap                               file            1921016 0       -3

If you wish to change the location, or size, of the generated swapfile please create the file /etc/dphys-swapfile and give it contents such as this:

# /etc/dphys-swapfile - user settings for dphys-swapfile package
# author Neil Franklin, last modification 2006.09.15
# copyright ETH Zuerich Physics Departement
#   use under either modified/non-advertising BSD or GPL license
# this file is sourced with . so full normal sh syntax applies

# where we want the swapfile to be, this is the default
CONF_SWAPFILE=/swap.file

# size we want to force it to be, default (empty) gives 2*RAM
CONF_SWAPSIZE=2048

##
#  Give yourself three times the memory size of swap?
#
# mem=$(grep MemTotal /proc/meminfo |awk '{print $2}')
# CONF_SWAPSIZE=$(expr $mem \* 3)
#

Etc

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