hakanekat's questions

I'm setting up bcache on ubuntu 20.04.

Booting from install CD, I created a bcache dirve by:

#modprobe bcache
#make-bcache -B /dev/mapper-vgubuntu-root
#make-bcache -C /dev/sdb

Just after that #fdisk -l showed /dev/bcache0. Then #mkfs.ext4 /dev/bcache0

and put all the files back from the backup.tar to the root of /dev/bcache.

Editted /etc/fstab like:

UUID=------- / ext4 erros=remount-ro 0 1

Then I updated grub by:

#mount -t ext4 /dev/bcache /mnt
#munt -B /dev /mnt/dev
#mount -B /proc /mnt/proc
#mount -B /sys /mnt/sys
#grub-install --recheck /dev/sda
#update-grub

Then I tried to restart the system from the new root /dev/bcache0. However, it fell into grub-rescue>,

saying "unknown file system UUID=-----".

I restarted the system from the install CD and checked whether or not the system recognized /dev/bcahe0.

#fdisk -l showed that the system didin't recognize it after boot.

Then

#modprobe bcache
#echo /dev/dm-0 > /sys/fs/bcache/register
#echo /dev/sdb > /sys/fs/bcache/register

With these commands fdisk -l showed /dev/bcache0.

/dev/mapper/vgubuntu-root is recognized as /dev/dm-0.

From the situation mentioned above, I think I have to update the initrd.img to execute the above scripts before the file system is mounted.

So I added bcache in /etc/initramfs-tools/modules

and wrote the following script to a file in /etc/initramfs-tools/scripts/init-premount/:

#! /bin/sh
echo /dev/dm-0 > /sys/fs/bcache/register
echo /dev/sdb > /sys/fs/bcache/register

I named the file 10_bcache.

Finally I update-initramfs and then restarted the system, however, the system still doesn't recognize /dev/bcache0 and falls into grub rescue mode.

How should I update-initramfs to recognize the bcache device before the system mounts the file system.

iriunwebcam (https://iriun.com) has worked fine on Ubuntu 20.04 LTS as well as on Ubuntu 20.04 beta on another VMware virtual machine, while it won't still work on a real PC. Also it works fine in Ubuntu 19.10 on another virtual machine. In addition I've confirmed it can work in Fedora 31 on another virtual machine.

The followings are the results of lsof -i before and after connected from a smartphone app.

1. on a virtual machine (20.04, 19.10, Fedora 31)

   (1) before connection from sp:

   COMMAND    PID      USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
   iriunwebc 2553 htakenaka   14u  IPv4  60002      0t0  UDP *:4698 
   iriunwebc 2553 htakenaka   15u  IPv6  60005      0t0  UDP *:4698 
   adb       2572 htakenaka    6u  IPv4  55976      0t0  TCP localhost:5037 (LISTEN)
   adb       2572 htakenaka   14u  IPv4  55962      0t0  UDP *:4698 
   adb       2572 htakenaka   15u  IPv6  55966      0t0  UDP *:4698 
   

   (2) after connection from sp:

   COMMAND    PID      USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
   iriunwebc 2078 htakenaka   22u  IPv4  73587      0t0  TCP Ubuntu1910-vmw:39256->192.168.79.201:4699 (ESTABLISHED)
   adb       2098 htakenaka    6u  IPv4  56531      0t0  TCP localhost:5037 (LISTEN)
   adb       2098 htakenaka   20u  IPv4  56514      0t0  UDP *:4698 
   adb       2098 htakenaka   21u  IPv6  56518      0t0  UDP *:4698 
   

2. on a real PC

   COMMAND    PID USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME  
   adb     117743 hiro    7u  IPv4 1420502      0t0  TCP localhost:5037 (LISTEN)  
   

From the above results iriunwebcam listens to 4698/udp port to find an available smartphone, and once the connection establishes, the port is closed and a tcp connection is established from a high port to the smartphone's 4699/tcp.

The problem on the real PC is that it cannot open 4698/udp port while 5037/tcp port can be opened both on virtual and real machines.

4698/udp and 5037/tcp are opened in the firewall both on virtual and real machines. Of course, if they are closed, iriunwebcam smartphone app cannot connect to PC app. However, PC app opens the ports even when the ports are closed.

I wonder why it cannot open 4698/udp port on the real PC.

The following is my environment.
_{Host (the real PC): iMac late 2011 (Core i3, 16GB RAM)
VMware Workstation 15.5.2 is used for virtual machines.
The virtual machines are bridged to the LAN through the host.
I'm not using NAT for virtual machines network interface.}

I've tried using iriunwebcam (https://iriun.com). At first I installed it in Ubuntu 20.04 beta on a VMware vitual machine and it successfully works. Then I installed it in Ubuntu 20.04 LTS on a real PC, however it doesn't work. The application itself successfully boots but it won't find the connection from the smartphone app.

lsof -i shows that iriunwebcam can open 4698/udp in 20.04 beta, but it can't in LTS. iriunwebcam seems to use the port to receive the connection from the smartphone app.

I wonder why it cannot open the port in 20.04. Is there anything changed from beta to LTS concerning socket connection or something else?