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Mirror

How would I create a mirror of HD0 and mirror it to HD1
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ntstud
Asked:
ntstud
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1 Solution
 
fmismettiCommented:
I assume that HD1 has a valid Linux partition, hdb1, and HDA is mounted as /.

1. mount /dev/hdb1 partition in /disk2 (this directory must exist).

2. Run this script:

#! /bin/bash
#
cd / && cp -a `/bin/ls -1A | egrep -v "^disk2$|^proc$"` /disk2

This will copy all files from "/" to "/disk2" except directories /disk2 and /proc (you can add more; use "^disk2$|^proc$|^tmp$" if you want to exclude also /tmp.

Last thing: the mirrored disk will not boot. If you want this, you need to do some tricks. Look in the document Hard-Disk-Upgrade mini-HOWTO. This document explains also another ways to duplicate your hard-disk (I learned about the method above there).

Let me know if this solves your problem.
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ntstudAuthor Commented:
Where would I setup the script, or just create a txt file and make it Xacutable?

new to scripts, NTstud remember!
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fmismettiCommented:
First, you did not explain the reason for reject the answer. I did not notice the "NTstud" and I had no means to know that you did not know how to setup scripts.

You can put this text in any text file, let's say /usr/myscripts/mirrordisk. Then you have two choices:

1. run "chmod +x /usr/myscripts/mirrordisk" and then you can just run the file from the command line.

2. run the plain text file invoking the shell and passing the text file as a parameter, like "/bin/bash /usr/myscripts/mirrordisk"


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vxCommented:
You could also use RAID-1 to mirror your disk. This way, all data will be written to two disks at the time, not just when you run the script.

For more information on RAID-1, have a look at:
http://metalab.unc.edu/LDP/HOWTO/mini/Software-RAID.html
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ntstudAuthor Commented:
thanks fmismetti, i will award you the points (answer again).

Danny

this WILL work right?  I have an ISP's server to mirror, silly rabbit, ISP are for pros.
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fmismettiCommented:
I have 6 servers using this script. It is not a really mirror as a raid that vx told. For my purposes I run this script twice a day, using crontab.

Also, with the information in the "Hard-Disk-Upgrade mini-HOWTO" I setup the second disk to be bootable and to have an entry in the /etc/lilo.conf like:

# Linux hdb1 bootable partition config begins
image = /vmlinuz
  root = /dev/hdb1
  label = LinuxB
  read-only
# Linux bootable partition config ends

Then you can press Shift-key when the system starts and choose to boot from the mirror. This is very confortable when you need to perform tasks like e2fsck in the primary disk or when something goes really wrong. The only thing you need to add to the script above is one line to fix the /etc/fstab from the second disk, like:

cp -a /etc/fstab.hdb /disk2/etc/fstab

fstab.hdb should be similar to you original fstab but referencing hdb instead of hda, like:

/dev/hdb2       swap     swap        defaults   1   1
/dev/hdb1       /        ext2        defaults   1   1
none            /proc    proc        defaults   1   1

Hope it helps you.
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fmismettiCommented:
Ops, I forgot that the rejected answer would be gone. here is a copy from my browser cache:

I assume that HD1 has a valid Linux partition, hdb1, and HDA is mounted as /.

1. mount /dev/hdb1 partition in /disk2 (this directory must exist).

2. Run this script:

#! /bin/bash
#
cd / && cp -a `/bin/ls -1A | egrep -v "^disk2$|^proc$"` /disk2

This will copy all files from "/" to "/disk2" except directories /disk2 and /proc (you can add more; use "^disk2$|^proc$|^tmp$" if you want to exclude also /tmp.

Last thing: the mirrored disk will not boot. If you want this, you need to do some tricks. Look in the document Hard-Disk-Upgrade mini-HOWTO. This document explains also another ways to duplicate your hard-disk (I learned about the method above there).

Let me know if this solves your problem.
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vxCommented:
Before you accept this answer, ask yourself the following question:
Do I want to make a backup or a mirror?

If you want to make a backup, you'd want to do as proposed. But this can be done only at specific times, so you won't have the latest copy of your disk.

If you want to make a mirror, you want the latest copy of your disk. With RAID-1, all data will be written to two disks simultaneously.
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