Category: Linux

To check if a file integrity is intact without expanding it, you can try the obvious send to /dev/null or use a built in equivilent

bzip2 -dc file.bz2 > /dev/null
bzip2 -tv file.bz2

Now, the problem can be that the split files were not complete ! so when i executed

cat file.bz2.001 file.bz2.002 file.bz2.003 file.bz2.004 > file.bz2

I thought that 004 was the last part, but it was not, how can i know without wasting CPU cycles ! let me show you

NOTE: If you have not yet concatenated the files, you can do the header checks on the first file, and the footer checks on the last 😉 in my case, I already have them concatenated (Not a problem, i can add more files to it later) so i am doing both checks on the same file

Check the header, Every bzip2 file starts with: 42 5a 68 xx

head -c4 file.bz2 | hexdump -C

Should result in

00000000  42 5a 68 39                                       |BZh9|

And it does

But when i check the footer with the command

tail -c64 file.tar.bz2 | hexdump -C

The first line of that output should be

00000000  17 72 45 38 50 90 00 00  00 00 00 00 00 00 00 00  |.rE8P...........|

But it is not, in my case it was

00000000  e4 fc 2e 36 2f e7 d5 bf  74 d5 3b 0f ef 4a 61 15  |...6/...t.;..Ja.|

Which looks like random compressed data

In conclusion, I should find all the other parts to be concatinated to this before wasting time decompressing it

Well, the calculator that ships with Gnome would launch instantly, then freeze instantly, I would then have to keep clicking the (x) in the corner and wait for the OS to suggest killing the app

No matter how long I wait on the app, it won’t budge, you can’t even move it around the screen

Turns out the calculator works if I am not connected to the internet (Pull the Ethernet cable out)

The solution was simple, it seems the calculator freezes waiting for data from the internet, when there is no internet, it skips the step

The solution was simple, it goes online for currency conversion rates, something i never use, so the solution is to execute the following command to stop it from doing that

dconf write /org/gnome/calculator/refresh-interval 0

Yup, that is it, the calculator works perfectly now

I am not sure that this problem is specific to my setup, where my audio comes from an nvidia 1650 passed through to a KVM virtual machine, but it seems that many people on bare metal are having this problem too

The problem occures randomly, and when it does, pipewire would be consuming a lot of CPU even though no audio is running

pipewire for those of you who don’t know is the new pulse audio, it comes with most modern distributions !

The solution when this happens for now sems to be to restart pipewire !

systemctl --user restart pipewire.service

If you were on a linux machine, it would be as simple as

ssh -L 5901:localhost:5901 root@192.168.7.119

Just kidding, don’t login as root, it is all just for tunneling, replace root and the IP of my super top secret server with something suitable

On windows, the most popular SSH client is putty, and to do that in putty, follow the following steps

Open putty, then enter the IP address or hostname of the remote machine

id3 tags were meant to be a simple way to store metadata in MP3 files, slowly but steadily, things became a bit more complicated

Originally, ID3 tags were meta data near the end of a file, then ID3V2 came along, and meta tags were moved to the beginning (With an ID3V1 copy at the end added by most ID3 editors)

Album artwork is another complication, As it may be embedded in the file, An older method used to depend on keeping an image called “cover.jpg” in the folder where the file is stored.

You can also have “user-defined fields”, which can be helpful if you are developing a music player that has some novel ideas

ID3 tag information can be obtained from gnudb.org, MusicBrainz, Discogs, Amazon

Gnome

• EasyTAG: GIT = tag editor for MP3, Ogg Vorbis files and more
  Written in C,
  Dep: libid3-3.8.3v5 libid3tag0 libopusfile0 – Suggested: libid3-tools

KDE

• KID3

LINUX Command Line

• id3:
• id3edit: GIT = id3edit is a command line ID3v2 tag editor and debugger

Windows

• MP3TAG: Freeware (Not free as in freedom), But great software nonetheless 😉

This is much simpler than you’d expect (provided there are no hardware passthoughs, and there usually isn’t), All you need to do is copy both the Disk and the XML file (Typically in /etc/libvirt/qemu) then

1- edit the following in the XML file

Create a new virtual machine ID

uuidgen

Create new MAC addresses for every network adapter

https://olavmrk.github.io/html-macgen/

Change the path to the disks to point to where you put the new copy of the disks

Thats it, now you need to tell KVM about it so….

2- Tell KVM about the new definition with the define function

virsh define /etc/libvirt/qemu/newxmlfile.xml

Hyper-v disk files, with extensions such as vhdx and vhd can be mounted under linux directly with the libguestfs-tools tool, mind you, many packages will be installed… mostly libraries relating to the formats it is capable of mounting

sudo apt-get install libguestfs-tools

Now, the following command should mount the disk inside the virtual machine

guestmount --add diskname.vhdx --inspector /mount/dir/name

If the system does not detect a system, you will need to tell guestmount what partition to mount, to explore the partitions, you will need ….

 virt-filesystems -a disk.vhdx

Once you know your partitions

guestmount --add disk_d.vhdx -m /dev/sda1  /hds/loop

If you would rather mount the disk as read only, you can add the –ro switch

guestmount --add yourVirtualDisk.vhdx --inspector --ro /mnt/anydirectory

To unmount, you will need to use the following command

guestunmount /mnt/anydirectory

VNC and RDP are great and all, and for so many purposes, they are the goto solution for remoting into a machine.

Now, another solution which is great (And much better if you have the bandwidth) is to broadcast your screen video and do all the work on the server rather than the client

The solution used to be nvidia’s game stream, which was abandoned by nvidia, the new solution based on nvidia would be the sunshine (Server) and moonlight client

The sunshine+moonlight duo work on almost every platform I need, Windows, Mac, Android, iOS, Even LG TVs running web OS… in short, it is a more universal solution. You can even create a virtual non existent monitor under linux and stream that to a different device !

So, let us start with the server (Sunshine)

Sunshine on debian

Installing sunshine on debian is very easy as a .deb installation file is provided, sunshine is not yet in the debian repositories, but if i understand the license correctly, it can be some time in the future

Now, go to the sunshine website, and download the deb file., in my case, I visit this webpage, and download the sunshine-debian-bookworm-amd64.deb file

Now, from the command prompt, su (to run as root), then cd to the directory where your deb file resides, then “sudo apt install ./sunshine-debian-bookworm-amd64.deb”, We should now have the server running and waiting to be opened in the web browser, Now, on the command line , type “sunshine”

Point a web browser to https://localhost:47990/, ignore the problem with self signed certificates, and set your username and password

Now, your debian computer is running a sunshine server, go to any other machine where you want to install the client (moonlight) from here , and connect to your server by its IP address.

You are done !

Sunshine on Windows

Download sunshine on windows from the latest release (As of today, you will fine it here)

Install it like you would any other application, once done, the official help page will show up (this)

once you click finish, a page at https://localhost:47990/welcome will open, asking you to create a password, create one, the default username is sunshine, but you can use whatever you want (In my case, it is my default RDP password)

you are done, you can now access the windows PC from any device with moonlight

Moonlight on Windows

you can download moonlight ether from github (Here) or from the official website (https://moonlight-stream.org/),

Before you start

This may look like a long post at first, but in reality, it is but a few commands, the rest is output and small simple explanations, so don’t be discouraged by the length, it is really neither complicated nor lengthy.

Yet, you do need to check the hardware requirements before you get your hands dirty, you will find them in the “Minimum hardware requirements” section of this post

UPDATE 2024-07-31: 8 months down the line, Still using this, and it works like a charm, No issues at all

Continue reading “GPU PCIe passthrough on KVM”

First, the tools you need

apt-get install qemu-utils

Now, enable NBD

modprobe nbd max_part=8

Once that is enabled, connect the file as a block device

qemu-nbd --connect=/dev/nbd0 /hds/usb/virts/Windows/main.qcow2

Now, the block device should appear like any other, alongside the partitions inside !

fdisk -l

On my machine, this resulted in

Disk /dev/nbd0: 95 GiB, 102005473280 bytes, 199229440 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0xc5324c42

Device      Boot     Start       End   Sectors  Size Id Type
/dev/nbd0p1 *         2048    104447    102400   50M  7 HPFS/NTFS/exFAT
/dev/nbd0p2         104448 198138958 198034511 94.4G  7 HPFS/NTFS/exFAT
/dev/nbd0p3      198139904 199225343   1085440  530M 27 Hidden NTFS WinRE

This disk was around 40GB, but fdisk will see the number corresponding to the largest allowed size, 100GB in this case ! let us mount the drive

mount /dev/nbd0p2 /hds/loop

Now, in this case in particular, like any other block device that held the windows operating system, more often than not, you will get the message saying

The disk contains an unclean file system (0, 0).
Metadata kept in Windows cache, refused to mount.
Falling back to read-only mount because the NTFS partition is in an
unsafe state. Please resume and shutdown Windows fully (no hibernation
or fast restarting.)
Could not mount read-write, trying read-only

The solution to that is simple, follow the following two steps to remedy the issue and then force mount the file by using remove_hiberfile

ntfsfix /dev/nbd0p2
mount -t ntfs-3g -o remove_hiberfile /dev/nbd0p2 /hds/loop

The result of NTFSFIX was

Mounting volume... The disk contains an unclean file system (0, 0).
Metadata kept in Windows cache, refused to mount.
FAILED
Attempting to correct errors...
Processing $MFT and $MFTMirr...
Reading $MFT... OK
Reading $MFTMirr... OK
Comparing $MFTMirr to $MFT... OK
Processing of $MFT and $MFTMirr completed successfully.
Setting required flags on partition... OK
Going to empty the journal ($LogFile)... OK
Checking the alternate boot sector... OK
NTFS volume version is 3.1.
NTFS partition /dev/nbd0p2 was processed successfully.

And the following mount command worked as you would expect, silently

Now, if you want to disconnect the NBD image, you need to unmount (Like you normally would) THEN

#Disconnect the image from the NBD device
qemu-nbd --disconnect /dev/nbd0;
#Unload the NBD module
rmmod nbd;