System.DllNotFoundException: Unable to load shared library 'libdl' or one of its dependencies

centos docker .net core 2.2報錯:

[2019-07-09 14:11:21 Error] Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware
An unhandled exception has occurred while executing the request.
System.TypeInitializationException: The type initializer for 'Gdip' threw an exception. ---> System.DllNotFoundException: Unable to load shared library 'libdl' or one of its dependencies. In order to help diagnose loading problems, consider setting the LD_DEBUG environment variable: liblibdl: cannot open shared object file: No such file or directory
   at Interop.Libdl.dlopen(String fileName, Int32 flag)
   at System.Drawing.SafeNativeMethods.Gdip.LoadNativeLibrary()
   at System.Drawing.SafeNativeMethods.Gdip..cctor()
   --- End of inner exception stack trace ---
   at System.Drawing.SafeNativeMethods.Gdip.GdipCreateBitmapFromScan0(Int32 width, Int32 height, Int32 stride, Int32 format, HandleRef scan0, IntPtr& bitmap)
   at System.Drawing.Bitmap..ctor(Int32 width, Int32 height, PixelFormat format)
   at Oshop.Services.Util.CaptchaUtil.GetCaptcha(String code) in /app/Oshop.Services/Util/CaptchaUtil.cs:line 32
   at curseIS.STS.Identity.Quickstart.Account.AccountController.GetCaptcha() in /app/base/curseIS.STS.Identity/Quickstart/Account/AccountController.cs:line 118
   at lambda_method(Closure , Object )
   at Microsoft.Extensions.Internal.ObjectMethodExecutorAwaitable.Awaiter.GetResult()
   at Microsoft.AspNetCore.Mvc.Internal.ActionMethodExecutor.TaskOfActionResultExecutor.Execute(IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at System.Threading.Tasks.ValueTask`1.get_Result()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeActionMethodAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeNextActionFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Rethrow(ActionExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ControllerActionInvoker.InvokeInnerFilterAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeNextResourceFilter()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Rethrow(ResourceExecutedContext context)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeFilterPipelineAsync()
   at Microsoft.AspNetCore.Mvc.Internal.ResourceInvoker.InvokeAsync()
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Localization.RequestLocalizationMiddleware.Invoke(HttpContext context)
   at IdentityServer4.Hosting.IdentityServerMiddleware.Invoke(HttpContext context, IEndpointRouter router, IUserSession session, IEventService events)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at IdentityServer4.Hosting.BaseUrlMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddleware.Invoke(HttpContext context)

項目使用了.net core下的Bitmap, 用來生成用戶注冊驗證碼, 使用的是如下dll:

using System.Drawing;
using System.Drawing.Imaging;

在win10上確實正常使用沒有問題, 在centos上用linux部署之后, 就一直報上面的錯誤.

有參考這些資料:

https://www.cnblogs.com/stulzq/p/10172550.html

https://www.cnblogs.com/stulzq/p/9339250.html

按步驟改了apt-get的源:

但是這樣改后會報別的錯:

The repository 'http://mirrors.163.com/debian jessie-backports Release' does not have a Release file

然后才在這發現:

debian 8.幾才用 jessie, 而.net core 2.2(我使用的版本), 使用的docker image是debian 9.9, 這樣查看:

radhat或centos存在：/etc/redhat-release 這個文件
debian或ubuntu 存在 /etc/debian_version 這個文件
Slackware存在 /etc/slackware_version 這個文件
ubuntu存在 /etc/lsb-release 這個文件

所以應該用stretch這塊的源:

deb http://mirrors.aliyun.com/debian/ stretch main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch main non-free contrib
deb http://mirrors.aliyun.com/debian-security stretch/updates main
deb-src http://mirrors.aliyun.com/debian-security stretch/updates main
deb http://mirrors.aliyun.com/debian/ stretch-updates main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch-updates main non-free contrib
deb http://mirrors.aliyun.com/debian/ stretch-backports main non-free contrib
deb-src http://mirrors.aliyun.com/debian/ stretch-backports main non-free contrib

不管怎樣, 改成這個源之后, 確實就可以了, 正常build 鏡像, 正常run起來, 正常的生成了驗證碼圖片, 惟一的別的事, 就是, 同一份代碼, 跑在win10上和linux docker里, 生成的圖片字體風格有差異:

centos docker:

win10:　　　　 

可以看出字母 y 還是有些不一樣, 不過, 這些小細節就不管那么多了.