A simple test for damaged disks

WARNING !!! ... This test will destroy the partition table and the beginning of the first partition. It can be done only as a last resort.

dd if=/dev/urandom of=test.img bs=65536 count=16

cat test.img > /dev/daX

dd if=/dev/daX of=test_rb.img bs=65536 count=16

diff test.img test_rb.img

If these files differs you have problems with disk.

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How to move centos system on a large disk

Hard Disk Upgrade Mini How-To

Instructions for PXE booting FreeBSD 9.x

There have been some changes in how PXE booting works with the release of FreeBSD 9.0. So I wanted to share some of what needs to be done to boot FreeBSD 9.0 via PXE.
The quick notes for people that have done PXE booting on prior versions of FreeBSD is:

• mfsroot is gone, so no config needed in /boot/loader.conf (i.e. it should be empty).
• Copy over the new pxeboot binary to your TFTP space, the old one will not work.

See below for a guide on how to get this working.

PXE Booting Guide

Prep the PXE Boot Server host

This is where the DHCP server, NFS Server and PXE Boot server will live. They could all easily live on different machines.

1. Download the FreeBSD 9 disc1 ISO from here: http://ftp.freebsd.org/pub/FreeBSD/releases/ISO-IMAGES/9.0/
2. Create a directory to store the files in:

   # mkdir /usr/public/freebsd90-amd64

3. Attach the iso as a device:

   # mdconfig -a -t vnode -f FreeBSD-9.0-RELEASE-amd64-disc1.iso

4. Mount the device:

   # mount_cd9660 /dev/md0 /mnt

5. Copy the files over:

   # cp -R /mnt/* /usr/public/freebsd90-amd64

6. Unmount the device:

   # umount /mnt

7. Detach the device:

   # mdconfig -d -u 0

8. Comment out the etc/fstab entry to mount from the cdrom media:

   # vi /usr/public/freebsd90-amd64/etc/fstab

9. Export the Directory via NFS in /etc/exports:

10. /usr/public/freebsd90-amd64 -ro

11. Wiew my article 

    Setup a NFS server on FreeBSD

       about how setup/run NFS Server.
12. Restart the mount daemon:

    # pkill -HUP mountd

13. Create a Directory for tftp files:

    # mkdir /usr/public/tftp

14. Enable tftp in /etc/inetd.conf:

    tftp    dgram   udp     wait    root    /usr/libexec/tftpd      tftpd -l -s /usr/public/tftp

15. Enable inetd in /etc/rc.conf:

    inetd_enable="YES"

16. Start inetd:

    # /etc/rc.d/inetd start

17. Copy over the pxeboot file to the tftp area:

    # cp /usr/public/freebsd90-amd64/boot/pxeboot /usr/public/tftp

18. Configure DHCPd:

    host fbsd9pxe {
     hardware ethernet xx:xx:xx:xx:xx:xx;
     fixed-address 192.168.1.45;
     next-server 192.168.1.10;
     filename "pxeboot";
     option root-path "/usr/public/freebsd90-amd64/";
    }

19. Enable DHCPd in /etc/rc.conf:

    dhcpd_enable="YES"

20. Start DHCPd:

    /usr/local/etc/rc.d/isc-dhcpd start

Modify the IP addresses and the MAC Address as needed for the environment in dhcpd.conf.

Boot your system

If everything went well you should be presented with the Installer ready to go.
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Setup a NFS server on FreeBSD

Lets begin:

1. % su
2. # echo 'nfs_server_enable="YES"' >> /etc/rc.conf
3. # echo 'rpcbind_enable="YES"' >> /etc/rc.conf
4. # echo 'mountd_flags="-r"' >> /etc/rc.conf
5. # echo 'rpc_lockd_enable="YES"' >> /etc/rc.conf
6. # echo 'rpc_statd_enable="YES"' >> /etc/rc.conf

By passing these options we guarantee that NFS related daemons are started at boot time. Steps 2 to 4 are mandatory and enable the NFS daemons, steps 5 and 6 are optional and are used to guarantee file locking operations over NFS and monitor NFS client so that the NFS server can free resources when the host disappears.

Lets proceed by identifying what we want to share:

1. % su
2. # vi /etc/exports
3. add the following line:

/usr/ports/distfiles -network 192.168.1 -mask 255.255.255.0

Step 3 shares the /usr/ports/distfiles directory and make it available to any client with an IP address beginning in 192.168.1 and netmask of 255.255.255.0.

Now that we've enabled the NFS server settings and configured the exports file, lets start the server by:

1. % su
2. # rpcbind
3. # nfsd -u -t -n 4
4. # mountd -r

If you perform any changes changes to the exports file, reload it by:

1. % su
2. # /etc/rc.d/mountd onereload

Also, the showmount command can be used to display the exports on the server:

1. % su
2. # showmount -e

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