An archive of solutions of programming problems I have faced in my career
If this happens, make sure clipboard sharing is enabled in the guest settings.
If it still doesn’t work, re-insert the VBox Additions ISO to the guest OS and reinstall VBox Additions, reboot guest OS and try again.
It may work for a while until eventually breaking again if Virtualbox is updated. After upgrading Virtualbox, usually there will be a new version of VBox Additions.
When the response header is too large, nginx will reject it and return 502 Bad Gateway, this is because the default proxy buffer size is not large enough.
If you inspect the error.log file under /var/nginx, you will find this error
upstream sent too big header while reading response header from upstream
Change the following settings under location to fix this issue by making the buffers larger
proxy_buffer_size 128k;
proxy_buffers 4 256k;
proxy_busy_buffers_size 256k;
After fixing this, if you encounter error: Request header or cookie too long. You can fix it by setting the buffer size for client header under server configuration context.
large_client_header_buffers 4 24k
This was really a lot of work as I’m not familiar with SSL and openssl. Took me a few days digging the net and trying many things to eventually make this work.
I was trying to make a Ubuntu client to trust a Windows webserver.
A few things I learned
Steps to do it
Instructions are from the below link
https://www.ibm.com/support/knowledgecenter/SSZQDR/com.ibm.rba.doc/LD_rootkeyandcert.html
Generate the private key of the root CA:
openssl genrsa -out rootCAKey.pem 2048
Generate the self-signed root CA certificate, with SAN, you need openssl 1.1.1
openssl req -x509 -sha256 -new -nodes -key rootCAKey.pem -days 3650 -out rootCACert.crt -addext “subjectAltName = DNS:<Your domain name>”
Refer to this stackoverflow question on how to add SAN: https://security.stackexchange.com/questions/74345/provide-subjectaltname-to-openssl-directly-on-the-command-line
Create a pfx file to install in Windows web server.
openssl pkcs12 -export -out rootCACert.pfx -inkey rootCAKey.pem -in rootCACert.crt -name “<Your domain name>”
Afterwards, import the pfx file to the certificate store of the Windows Server using Microsoft Management Console and configure your webserver to use this certificate.
For Ubuntu Client, install to ca-certificates
sudo cp rootCACert.crt /usr/local/share/ca-certificates
sudo update-ca-certificates
Test using cURL, you may need to configure DNS or hosts file
curl https://<Your domain name>
Chrome and Firefox use their own certificate stores, so you need to add the certificates through their settings GUI. cURL will still work if cert doesn’t have SAN, but Chrome will complain as mentioned above.
When trying to use the code first approach of Entity Framework Core to generate database and tables using MySQL. When running Update-Database in the package console manager, it shows an error saying table __efmigrationhistory doesn’t exists.
After digging in Stackoverflow, it seems that it’s a bug with the official MySQL connector. And at the time of this writing with this version 8.0.20 and .NET Core 3.1, this bug hasn’t been fixed. The connector is supposed to create this table for migration.
https://stackoverflow.com/a/46090571/9191495
In order to solve this problem there are two solutions
-Don’t use the official connector, use Pomelo.EntityFramework.MySql
https://www.nuget.org/packages/Pomelo.EntityFrameworkCore.MySql
-Alternatively create, the table yourself
CREATE TABLE `__EFMigrationsHistory`
(
`MigrationId` nvarchar(150) NOT NULL,
`ProductVersion` nvarchar(32) NOT NULL,
PRIMARY KEY (`MigrationId`)
);It’s a waste of time, but what can one do.
This is a stupid mistake.
Make sure that in launch.json, the value for cwd is correct and is pointing to the same folder as the DLL of the .NET Core app.
By default current working directory is set to the workspace directory, the appsettings.json file is not there, thus when running the app, it doesn’t have any settings.
In Ubuntu desktop 18.04, it seems that in order to change the DNS server, you need to open Network Manager in the UI and set the DNS server IP Address.
However it doesn’t work until you restart or run sudo netplan apply.
If you use Ubuntu server, you need to modify a yaml file within yaml file, then run netplan apply.
Not sure why doing so in Ubuntu desktop doesn’t work, though.
This happens if ASP.NET 1.1 is installed and then uninstalled for some reason.
To fix, open IIS Manager, go to the website, under ISAPI filters, remove the aspnet_filter handler. After that, the error should go away.
When reading processed historical data from OPC UA server, if you don’t set processing interval, only one value will be returned.
So if you use aggregation function Max from StartTime to EndTime, if you don’t specify the processing interval, it will return the maximum value from start time to end time.
If you specify the processing interval to 1 hour, it will return multiple max values for each hour within StartTime to EndTime.
Search for “Turn Windows features on or off” and enable features under IIS -> WWW Services -> Application Development Features.
Enable ASP.NET 3.5 or 4.8, one of the features will enable handlers.
Maybe <handlers> is for ASP.NET Http Handlers.
Refer to this link: https://social.technet.microsoft.com/Forums/windows/en-US/6e133d2c-d0b8-48b0-8b32-94d6b010a224/server-does-not-appear-under-network?forum=w7itpronetworking
“Network discovery requires that the DNS Client, Function Discovery Resource Publication, SSDP Discovery, and UPnP Device Host services are started, you may check this on both sides to make sure they are started.”