Data recovery from a dead Netgear ReadyNAS Duo

I found the following pages helpful:

https://superuser.com/questions/1031283/how-to-get-the-data-off-of-a-readynas-drive
https://jim-st.blogspot.com/2012/07/mouning-readynas-drives-on-x86-systems.html
https://technostuff.blogspot.com/2012/06/how-to-mount-disk-used-by-readynas.html

I found that the right-hand drive was mountable, but required installation of some packages on a Fedora 29 desktop system:

git clone https://github.com/alperakcan/fuse-ext2.git
dnf install autoconf automake libtool
dnf install libfuse-dev e2fsprogs comerr-dev e2fslibs-dev
dnf install fuse-libs fuse3-libs
dnf install fuse-devel fuse3-devel
https://fedora.pkgs.org/29/fedora-x86_64/libcom_err-devel-1.44.3-1.fc29.x86_64.rpm.html
dnf install Downloads/libcom_err-devel-1.44.3-1.fc29.x86_64.rpm
dnf install e2fsprogs-libs e2fsprogs-devel

Next steps:

vgchange -ay c
lvscan
fuse-ext2 -o sync_read,allow_other,rw+ /dev/c/c /mnt/tmp

Data now accessible in /mnt/tmp

Installing Win7 guest on KVM with CentOS 7

Installation with virt-manager is fairly straightforward. However, unfortunately, this results in a guest that uses the very slow IDE disk driver. Changing to use virtio is a little tricky - this blog post was very helpful: http://setdosa.blogspot.com/2013/09/moving-your-windows-guest-from-ide-to.html

This is a general handy guide: 
https://support.opennodecloud.com/wiki/doku.php?id=usrdoc:os:win-guest

Installing Win7 guest in Virtualbox from a USB stick image

1. Use dd to make an image file of the entire stick - e.g. dd if=/dev/sdg of=usb_stick.img
2. Copy to target machine.
3. Convert to .vmdk file using: "VBoxManage internalcommands createrawvmdk -filename output_usb.vmdk -rawdisk usb_stick.img (thanks to: http://www.dallagnese.fr/en/computers-it/boot-on-your-usb-drive-in-virtualbox-4/ ).
4. Add the image file to the SATA controller as a hard drive. Make sure it has lowest SATA port number.

SSH via intermediate host

In terminal on local machine:

$ ssh -f -N -L6969:localhost:6969 intermeduser@intermedhost
$ ssh intermeduser@intermed
intermedhost$  ssh -f -N -L6969:localhost:22 destuser@desthost

Then, in other local terminals:

$ ssh -p 6969 destuser@localhost

Updating Seagate Barracuda 7200.11 drive firmware on a Dell Optiplex 960

This was a real head-scratcher, because Seagate's ISO image would NOT boot on this machine, whether burnt to a CD or written to a flash drive with unetbootin.

I eventually succeeded by extracting the El Torito floppy image from the ISO using http://freecode.com/projects/geteltorito and then putting the files on a FreeDOS bootable flash drive using unetbootin.

I also found that unetbootin/FreeDOS requires a FAT16 formatted primary partition on the flash drive to work properly.

Obscure xinetd tip

If you have a "wait=yes" server bound to 127.0.0.1, you can get a syslog full of messages like this:

xinetd[25741]: warning: can't get client address: Transport endpoint is not connected

The trick is to add "flags=NOLIBWRAP".

THis bug report gives a clue as to the underlying cause: https://bugzilla.redhat.com/show_bug.cgi?id=108583

Migrating a guest VM with Xen 3.2

'xen migrate' didn't work - it hung, as others have reported.

It turned out to be as simple as:

1. Stop the original guest.
2. Copy the disk image and the config files ( in /etc/xen/vm) to the new host.
3. Execute 'xm create guest-name' on the new host.
4. Done!