Scribbles for my bad memory

The biggest problem you faced is actually the following one
https://otodiginet.com/operating-system/how-to-install-snapd-on-centos-8/

and the article above answers the question very well.

certbot certos

1. Create a middleware to do that task

    public static void SetCurrentCulture(this IApplicationBuilder app)
    {
        app.Use(async (context, next) =>
        {
            var cultureQuery = context.Request.Headers["lang"] == "en" ? "en-US" : "zh-CN";
            if (!string.IsNullOrWhiteSpace(cultureQuery))
            {
                var culture = new CultureInfo(cultureQuery);
                CultureInfo.CurrentCulture = culture;
                CultureInfo.CurrentUICulture = culture;
            }
            await next();
        });
    }
   

2. Use the middleware in Startup.cs

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILog logger,
        IExceptionEntityService exceptionEntityService)
    {
        ...
        app.SetCurrentCulture();
        ...
    }
   

Cause:

This morning, I change to the /backup directory and found I cannot write in it. So I rapidly typed sudo chown -R david:david .. then press Enter. You know what happened! All the files in / directory were changing the owner to me! I realized this by seeing an error message like "You cannot change the owner of xxx file to david".

Damn, how silly I was! Unfortunately, that was not the end of my bad luck. When I try to revert it by typing sudo chown -R root:root /, I got another error message: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set. Then I tried su - root but it seems that I haven't set a root password.

How can I recover my pop! OS?

1. reboot it into single-user mode, edit the boot menu, add systemd.unit=rescue.target at the end of the boot line.
2. In the boot console, chown -R root:root /usr; chmod 4755 /usr/bin/{sudo,dpkg,pkexec,crontab}; reboot

Rather easy, right? It did cost me over 10mins! PS. I met many issues later after recovering from the accident. One of them is that the crontab command did not work as usual. I have to run the instruction below to fix it.

sudo apt reinstall cron

Linux is also fragile, please don't be such silly thing next time. I told myself. PS: This time I also set a root password as well, so next time I could run su - root directly instead of going to the single user mode.

In short:

Change the service file, and add two lines after [Service] line,

[Service]
LimitNOFILE=65535
LimitNOFILESoft=65535

If you want to know more, read the Reference