Category Archives: Ubuntu

“Server certificate verification failed” error with command line Git client

Some guy described the same situation about 10 years ago on and there was another discussion about 7 years ago.

First I did:

GIT_CURL_VERBOSE=1 git clone
Cloning into 'examples'...
* Couldn't find host in the .netrc file; using defaults
*   Trying
* Connected to ( port 443 (#0)
* found 129 certificates in /etc/ssl/certs/ca-certificates.crt
* found 387 certificates in /etc/ssl/certs
* ALPN, offering http/1.1
* SSL connection using TLS1.2 / ECDHE_RSA_AES_256_GCM_SHA384
* server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none
* stopped the pause stream!
* Closing connection 0
fatal: unable to access '': server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none

Compiling Awl on Ubuntu 18 and 20 with GCC 11

Below I provided the instruction on how to build Awl on Ubuntu 18 and 20.

On Ubuntu 18 you do an extra step to install CMake version >= 3.12:

wget -O - 2>/dev/null | sudo apt-key add -
sudo apt-add-repository 'deb bionic main'
sudo apt update

Then do the following steps on both Ubuntu 18 and 20:

sudo apt install cmake
cmake --version

Error reading file: No space left on device

I had a large SQLite file C:\Users\D-Ef\AppData\Local\TradeClient\realtime.db that I was unable to copy to another disk. I tried:

split -n 10 -d -u realtime.db /mnt/d/db/rt
dd bs=65536 if=realtime.db of=/mnt/d/db/rt

in WSL, but got ‘error reading ‘realtime.db’: No space left on device’ with all the commands.

Finally I reduced page file size restarted my machine and copied the file in a usual way.


Installing Jabber Messaging Service on Ubuntu 16.04

sudo apt install ejabberd
ufw allow to any port 5280 proto tcp
ufw allow to any port 5222 proto tcp
ufw allow to any port 5269 proto tcp
ufw allow to any port 7777 proto tcp
sudo nano /etc/ejabberd/ejabberd.yml
## hosts: Domains served by ejabberd.
## You can define one or several, for example:
## hosts:
##   - ""
##   - ""
##   - ""
  - ""


###.   ====================
  ## The 'admin' ACL grants administrative privileges to XMPP accounts.
  ## You can put here as many accounts as you want.
         - "admin": ""

A proper Ubuntu 18.04 installation for running Ethereum node

Create a Hyper-V machine with a disk that is large enough:

And install Ubuntu 18.04.


Installing Oracle Database 19.3 in a Docker container on Ubuntu Server 18.04

First I installed Ubuntu Server 18.04 as a Hyper-V machine on Windows 10.

While creating the virtual machine I selected Generation 1, because Generation 2 resulted in some strange effects.

Then I created a separate user with sudo permission:

sudo useradd -d /home/singh -m --shell "/bin/bash" singh
sudo passwd singh
sudo usermod -aG sudo singh

Binding Docker container ports to the host on Ubuntu 18.04 inside Hyper-V on Windows 10

The binding did not work for me until I switched from Internal Virtual Switch to External Virtual Switch and while switching I were getting the following error:

[Window Title]
Virtual Switch Manager for MY-MACHINE

[Main Instruction]
Error applying Virtual Switch Properties changes

Failed while adding virtual Ethernet switch connections.

[Expanded Information]
External Ethernet adapter 'Realtek PCIe GBE Family Controller' is already bound to the Microsoft Virtual Switch protocol.

until I switched Hyper-V Extensible Virtual Switch off on my network adapter properties page (after I created External Virtual Switch it switched on back):


Timed out waiting for device dev-disk-by/… while booting Ubuntu 18.04 up.

My Ubuntu 18.04 installed in Windows 10 HyperV virtual machine stopped booting up with the following errors:


Setting up time synchronization on Ubuntu

I followed the official Ubuntu time synchronization guide and installed chrony:

sudo apt update
sudo apt install chrony
cat /etc/chrony/chrony.conf
chronyc sources
chronyc sourcestats
sudo systemctl restart chrony.service
apt remove --autoremove chrony


Setting up Ethereum node on Windows 10 and Ubuntu.

After a few attempts I was able to start Ethereum Mist 0.11.1 in ‘fast’ mode on Windows 10:

it downloaded ‘geth’, connected to {“path”:”\\\\.\\pipe\\geth.ipc”} and started to sync, but when sync finished I was unable to send transactions (they were ‘denied’ for some reason).