Hard Disk Upgrade Mini How-To

1. Introduction

This document explains how to transfer, or migrate, an entire Linux system, including LILO, from one hard disk to another.

In the following explanation, /dev/hda (first IDE hard disk) means the old disk, and /dev/hdb (second IDE hard disk) means the new disk.

Specific partitions on the old disk are referred to as /dev/hda1, /dev/hda2, and so on. Specific partitions on the new disk are referred to as /dev/hdb1, /dev/hdb2, and so on.

The explanations in this document are based on Red Hat 6.0. They have also been tested with Debian 2.1, Slackware 3.5 and SuSE 6.2; we indicate a few differences to note if you're using those distributions.

If the commands don't work properly on your system, please let us know, mentioning what distribution you're using.

2. Install both disks on your system

Modern systems can accept four EIDE devices on the hard disk controller, so there shouldn't be any problem installing both disks on your system at the same time, even if you also have other EIDE devices. Hard disks and CD-ROM drives are typical EIDE devices. Floppy drives and tape drives are usually connected to the floppy drive controller rather than to the hard disk controller.

SCSI adapters are even more flexible and can accept seven devices. If you're lucky (and rich) enough to have a SCSI adapter, you probably already know this, and you probably know which of your devices are SCSI devices! For more information, see the SCSI How-To.

Even the oldest systems can accept two devices on the hard disk controller, so you can still install both hard disks at the same time. However, if you already have another device installed in addition to your hard disk (for example, if you have both a hard disk and a CD-ROM drive), you'll have to remove the other device to be able to install the old hard disk and the new hard disk at the same time.

You must configure the disks as master or slave by installing the disks' jumpers as appropriate. You'll often find configuration information on the disks themselves; if not, consult the manuals or the disks' manufacturers.

You must also inform the BIOS of the disks' presence and of their geometry. Usually, you enter the BIOS setup program by pressing a key during the system boot-up. Here's what to do for some common BIOSes:

Reboot the system and login as root. If you use the su command to become the user root, use su -, with the hyphen option.

3. Unmount non-Linux partitions and network drives

Some people like to mount partitions from other operating systems (DOS, Windows, OS/2, etc.) so they can use them under Linux. These partitions must be created and copied under their own operating system, and you should unmount them before copying your Linux partition. For example, if you have a DOS partition mounted at /dos, you must unmount it with this command:

umount /dos

Note that the command is umount, without the first letter n in the word unmount.

You should also unmount network drives.

4. Partition the new disk

Use this command to partition the new disk:

fdisk /dev/hdb

EIDE devices are identified as hda, hdb, hdc, and hdd in the /dev directory. Partitions on these disks can range from 1 to 16 and are also in the /dev directory. For example, /dev/hda4 refers to partition 4 on hard disk a (first EIDE hard disk).

SCSI devices are listed as devices sda, sdb, sdc, sdd, sde, sdf, and sdg in the /dev directory. Similarly, partitions on these disks can range from 1 to 16 and are also in the /dev directory. For example, /dev/sda3 refers to partition 3 on SCSI disk a (first SCSI hard disk).

For Linux partitions with the ext2 file system, use system ID 83. For swap partitions, use system ID 82.

For more information on partitioning, see the Installation How-To and the Partition Mini How-To.

If your new disk has over 1024 cylinders, see the Large Disk Mini How-To. In brief, you should install all files required to boot Linux within the first 1024 cylinders. One way to do this is to create a small partition (5 Mb or so) just for the /boot directory at the beginning of the disk. (Slackware only: The kernel is at /vmlinuz rather than /boot/vmlinuz, so you should put both the / directory and the /boot directory in this partition.)

Partitions for systems other than Linux should be created using their own fdisk or equivalent command rather than with Linux's fdisk.

5. Format the new disk

Use the following command to format Linux partitions using ext2fs on the new disk:

mkfs.ext2 /dev/hdb1

To check the disk for bad blocks (physical defects), add the -c option just before /dev/hdb1.

If the new disk will have more than one Linux partition, format the other partitions with mkfs.ext2 /dev/hdb2, mkfs.ext2 /dev/hdb3, and so on. Add the -c option if desired.

With older distributions, the command mkfs -t ext2 -c /dev/hdb1 didn't check for bad blocks under any of Red Hat, Debian or Slackware, contrary to what the man page stated. This has now been fixed.

To format a swap partition, use this command:

mkswap /dev/hdb1

Again, you can add the -c option before /dev/hdb1 to check for bad blocks.

6. Mount the new disk

Create a directory where you'll mount the new disk, for example /new-disk, and mount it there:

mkdir /new-disk
mount -t ext2 /dev/hdb1 /new-disk

If the new disk will have more than one Linux partition, mount them all under /new-disk with the same organization they'll have later.

/dev/hdb1:    /
/dev/hdb2:    /home
/dev/hdb3:    /var
/dev/hdb4:    /var/spool

Mount the four partitions under /new-disk as follows:

/dev/hdb1:    /new-disk
/dev/hdb2:    /new-disk/home
/dev/hdb3:    /new-disk/var
/dev/hdb4:    /new-disk/var/spool

You must create the mount points for each level before you mount the partitions at that level.

mkdir /new-disk                                 [1st level]
mount -t ext2 /dev/hdb1 /new-disk

mkdir /new-disk/home                            [2nd level]
mount -t ext2 /dev/hdb2 /new-disk/home

mkdir /new-disk/var                             [2nd level also]
mount -t ext2 /dev/hdb3 /new-disk/var

mkdir /new-disk/var/spool                       [3rd level]
mount -t ext2 /dev/hdb4 /new-disk/var/spool

If you've created a mount point at /new-disk/tmp, you'll need to correct the directory's permissions to let all users access it:

chmod 1777 /new-disk/tmp

7. Copy the files from the old disk to the new disk

You might want to go to single-user mode before starting to copy the disk, in order to shut down the system daemons and preserve the state of the logs, and to prevent users from logging in:

/sbin/telinit 1

When copying the hard disk, you want to copy all directories and files, including links.

However, you don't want to copy the directory /new-disk, since this would copy the new disk to itself!

Furthermore, you want to create the /proc directory on the new disk, but you don't want to copy its contents: /proc is a virtual file system and doesn't have any actual files, but rather contains information on the processes running on the system.

Here are three different ways to copy the old disk to the new one. This may take quite a while, especially if you have a large disk or little memory. You can expect to be able to copy 10 Mb per minute, and possibly much more.

You can follow the copy's progress by using the command df from another terminal. Try watch df or watch ls -l /new-disk to see a report updated every two seconds; press Ctrl-C to end the display. Be aware that running the watch program itself will slow down the copying.

Previous versions of the Mini How-To stated that you could also use tar to copy the disk, but this method was found to have a bug. There are of course many other ways to copy the disks, but these three are the simplest, quickest, and most reliable.

After using any of these three methods, you must also create the /proc directory on the new disk, if it doesn't already exist:

mkdir /new-disk/proc

At this point, you may verify the file structure on the new disk, if you wish:

umount /new-disk
fsck.ext2 -f /dev/hdb1
mount -t ext2 /dev/hdb1 /new-disk

If the new disk has more than one partition, you must unmount them from the bottom up before running fsck.ext2: in the example mentioned above, you'd first unmount the 3rd level partitions, then the 2nd level partitions, and then the 1st level partition.

You may also compare the two disks, to ensure that the files were copied properly:

find / -path /proc -prune -o -path /new-disk -prune -o -xtype f -exec cmp {} /new-disk{} \;

(write this all on one line)

This will only compare regular files, not character or block special files (in the /dev directory), sockets, etc., since the cmp command doesn't work properly with these. We would welcome suggestions on how to verify these "special" files.

8. Modify /new-disk/etc/fstab as appropriate

If your new disk doesn't have the same partitions or organization as the old disk, modify the file /new-disk/etc/fstab on the new disk as appropriate.

Make sure that the disk partitions (first column) correspond to the organization you'll have with the new disk, once the old disk has been removed, and that you're only mounting one partition at / as shown in the second column.

For more information on the format of the file /etc/fstab, see the Linux System Administrator's Guide, section 4, under Mounting and unmounting.

For swap partitions, use a line similar to this one:

/dev/hda1   swap    swap    defaults    0  0

9. Prepare LILO to boot the new disk

We're assuming that LILO is installed on the hard disk's Master Boot Record (MBR); this seems to be the most common configuration. You want to install LILO on what's presently the second hard disk but will become the first hard disk.

Edit the file /new-disk/etc/lilo.conf as follows:

disk=/dev/hdb bios=0x80       # Tell LILO to treat the second
                              # disk as if it were the first
                              # disk (BIOS ID 0x80).
boot=/dev/hdb                 # Install LILO on second hard
                              # disk.
map=/new-disk/boot/map        # Location of "map file".
install=/new-disk/boot/boot.b # File to copy to hard disk's
                              # boot sector.
prompt                        # Have LILO show "LILO boot:"
                              # prompt.
timeout=50                    # Boot default system after 5
                              # seconds. (Value is in tenths of
                              # seconds.)
image=/new-disk/boot/vmlinuz  # Location of Linux kernel. The
                              # actual name may include a version
                              # number, for example
                              # "vmlinuz-2.0.35".
    label=linux               # Label for Linux system.
    root=/dev/hda1            # Location of root partition on
                              # new hard disk. Modify this as
                              # appropriate for your system.
                              # Note that you must use the name
                              # of the future location, once the
                              # old disk has been removed.
    read-only                 # Mount partition read-only at
                              # first, to run fsck.

If you're using a SCSI hard disk, you may have to add a line with initrd. See your existing file /etc/lilo.conf.

Install LILO on the new disk:

/sbin/lilo -C /new-disk/etc/lilo.conf

The -C option tells LILO what configuration file to use.

10. Make a boot diskette (optional)

If you wish, you can make a boot diskette, in case you run into problems when trying to boot the new disk.

Insert an empty diskette, format it, create a file system on it and mount it:

fdformat /dev/fd0H1440
mkfs.ext2 /dev/fd0
mount -t ext2 /dev/fd0 /mnt

Copy all files in /boot to the diskette:

cp -dp /boot/* /mnt

Create a new file /mnt/lilo.conf as follows:

boot=/dev/fd0                 # Install LILO on floppy disk.
map=/mnt/map                  # Location of "map file".
install=/mnt/boot.b           # File to copy to floppy's
                              # boot sector.
prompt                        # Have LILO show "LILO boot:"
                              # prompt.
timeout=50                    # Boot default system after 5
                              # seconds. (Value is in tenths of
                              # seconds.)
image=/mnt/vmlinuz            # Location of Linux kernel on
                              # floppy. The actual name may
                              # include a version number, for
                              # example "vmlinuz-2.0.35".
    label=linux               # Label for Linux system.
    root=/dev/hda1            # Location of root partition on
                              # new hard disk. Modify this as
                              # appropriate for your system.
                              # Note that you must use the name
                              # of the future location, once the
                              # old disk has been removed.
    read-only                 # Mount partition read-only at
                              # first, to run fsck.

Install LILO on the boot diskette:

/sbin/lilo -C /mnt/lilo.conf

The -C option tells LILO what configuration file to use.

Unmount the diskette:

umount /mnt

11. Remove the old disk

Shut down the system and remove the old disk. Remember to modify the disk jumpers and the BIOS information to reflect the changes.

12. Reboot the system, modify LILO configuration file

Reboot the system. If you have problems, you can use the boot diskette you just make. To do so, you may have to modify your BIOS's boot-up sequence to A:, C:.

You should modify the file /etc/lilo.conf in case you later want to run LILO again. Here's an example of how the file can look:

boot=/dev/hda                 # Install LILO on first hard
                              # disk.
map=/boot/map                 # Location of "map file".
install=/boot/boot.b          # File to copy to floppy's
                              # boot sector.
prompt                        # Have LILO show "LILO boot:"
                              # prompt.
timeout=50                    # Boot default system after 5
                              # seconds. (Value is in tenths of
                              # seconds.)
image=/boot/vmlinuz           # Location of Linux kernel. The
                              # actual name may include a version
                              # number, for example
                              # "vmlinuz-2.0.35".
    label=linux               # Label for Linux system.
    root=/dev/hda1            # Location of root partition on
                              # new hard disk. Modify this as
                              # appropriate for your system.
    read-only                 # Mount partition read-only at
                              # first, to run fsck.

13. Acknowledgements

Thanks to Scott Christensen, Frank Damgaard, Alexandre Fornieles, David Fullerton, Igor Furlan, Jerry Gaines, Chris Gillespie, Nicola Girardi, Per Gunnar Hansoe, Richard Hawes, Ralph Heimueller, Gerald Hermant, Andy Heynderickx, Paul Koning, Hannu Liljemark, Claes Maansson, Rick Masters, Jason Priebe, Josh Rabinowitz, Douglas Rhodes, Valentijn Sessink, Kragen Sitaker, Stephen Thomas, and Gerald Willman.

This document may be translated into any language. If you do so, please send a copy of the translation to Konrad Hinsen <hinsen@cnrs-orleans.fr>.