Application error

Question

Application error

Amit Developer- Atlantic 20

Hi there, I created a web app. when I deploy my code its shows an error on front end "Application Error"

Divyesh Govaerdhanan 6,400 Reputation points

2025-05-04T16:19:10.51+00:00
Hello,

Application error indicates the runtime error on your front-end application. You can check App Service logs to identify the error. Please check the below,

In App Service, Under Monitoring

Log stream → Real-time logs

Diagnose and solve problems → Quick insights on issues

Application Logs (if configured)

With detailed errors on the above monitoring options, you will be able to fix the application error in your application.

Please Upvote and accept the answer if it helps!!
Amit Developer- Atlantic 20 Reputation points

2025-05-05T09:59:58.79+00:00

How can I install wkhtmltopdf and use the path in my app.py code
Alekhya Vaddepally 1,670 Reputation points Microsoft External Staff Moderator

2025-05-05T10:38:48.83+00:00
Hi Amit Developer- Atlantic,

When you use wkhtmltopdf in your python app (often through libraries like PDFKIT), this requires Wkhtmltopdf binary to be installed and accessible from the system path. If the binary is missing or the path is not set correctly, the app will throw an error - which in the production environment, can only appear as a "app error" without a wide log.

Install wkhtmltopdf on the server:

If you are using Azure App Service (Linux or Windows), then you need to manually install wkhtmltopdf as it is not pre-installed by default.

For Linux app services, use a startup script to install it:

apt-get update apt-get install -y wkhtmltopdf

For Windows app services, it is more complex since installing a system-wide tool, not straightforward. You may need to include wkhtmltopdf binary in your project and call it using the absolute path.

Wkhtmltopdf

bundle in your app directory:

Download the binary from the official wkhtmltopdf site and include it in a folder (eg, bin/) in your project.

Update your app.py to use the right path:

Here is an example of how to clearly configure the path in Python:

import pdfkit config = pdfkit.configuration(wkhtmltopdf='/absolute/path/to/wkhtmltopdf') pdfkit.from_url('http://google.com', 'out.pdf', configuration=config)

Change '/absolute/path // wkhtmltopdf' with the actual path to your server or bundle location.

After deploying these changes, restart your app.

https://learn.microsoft.com/en-us/azure/app-service/configure-custom-container?pivots=container-linux&tabs=debian
https://learn.microsoft.com/en-us/azure/app-service/quickstart-python?tabs=flask%2Cwindows%2Cazure-cli%2Cazure-cli-deploy%2Cdeploy-instructions-azportal%2Cterminal-bash%2Cdeploy-instructions-zip-azcli
if you have any further concerns or queries, please feel free to reach out to us.
Amit Developer- Atlantic 20 Reputation points

2025-05-05T11:46:41.97+00:00

I am getting this error in bash
E: List directory /var/lib/apt/lists/partial is missing. - Acquire (13: Permission denied)

E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)

E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
Alekhya Vaddepally 1,670 Reputation points Microsoft External Staff Moderator

2025-05-05T13:15:32.3233333+00:00
Hi Amit Developer- Atlantic,
You are getting many permission errors because the command you are running (such as APT-Get Update or APT-GET Install) requires root privileges, but the shell you are using (possibly your deployment or inside the Azure App service environment) is not root shell).

This is why you are seeing:

Not allowed permission

Are you root

To solve these permission issues, you have to prefix the command with the Sudo (if the sudo is available in your environment):

sudo apt-get update sudo apt-get install -y wkhtmltopdf

If you are running in restricted environment like Azure App Service (Linux), you may not have the use of Sudo. In such cases, the recommended approach is:

Create a file named startup.sh in your project directory with these contents:

#!/bin/bash apt-get update && apt-get install -y wkhtmltopdf gunicorn --bind=0.0.0.0 --timeout 600 app:app

Make it executable (if running locally):

chmod +x startup.sh

Configure your Azure App to use Custom Startup Command: Go to Azure Portal> App Services> Configuration> General Settings. Set Startup Command:

/home/site/wwwroot/startup.sh

Deploy your app with the startup.sh file included.
https://learn.microsoft.com/en-us/azure/app-service/configure-custom-container?pivots=container-linux&tabs=debian
https://learn.microsoft.com/en-us/azure/app-service/configure-language-python?pivots=python-framework-flask%2Cpython-3.9#customize-startup-command
Amit Developer- Atlantic 20 Reputation points

2025-05-05T13:42:09.6566667+00:00

Now i am getting this error
wkhtmltopdf exited with non-zero code 127. error: /tmp/8dd8bcfb4d3405c/bin/wkhtmltopdf: error while loading shared libraries: libjpeg.so.62: cannot open shared object file: No such file or directory
Alekhya Vaddepally 1,670 Reputation points Microsoft External Staff Moderator

2025-05-05T14:16:07.6966667+00:00
Hi Amit Developer- Atlantic,
Option1:Install Dependencies via Startup Script (Best for Azure App Service Linux)

Modify your startup.sh to install the missing dependencies before starting your app:

#!/bin/bash apt-get update && apt-get install -y \ libjpeg62-turbo \ libxrender1 \ libxext6 \ xfonts-base \ xfonts-75dpi \ wkhtmltopdf gunicorn --bind=0.0.0.0 --timeout 600 app:app

It installs Libjpeg62-Turbo, which provides Libjpeg.so.62. Also ensure that this is the script: Saved in his project directory, marked as executable, and Configured as a startup command in Azure.
https://learn.microsoft.com/en-us/azure/app-service/configure-custom-container?pivots=container-linux&tabs=debian
https://learn.microsoft.com/en-us/azure/app-service/overview#supported-linux-distributions
Option2:Use the fully bundled Wkhtmltopdf build (portable static version)

Download the static (self-contained) Linux Build of Wkhtmltopdf from his official site:

https://wkhtmltopdf.org/downloads.html

Use a version like wkhtmltox-0.12.6-1.alpine3.17_x86_64.apk.tar.gz or wkhtmltox-0.12.6-1-centos7-amd64.tar.xz

Remove it in your project (/bin) folder.
Update your Python code to use the bundled path:

import pdfkit config = pdfkit.configuration(wkhtmltopdf='/home/site/wwwroot/bin/wkhtmltopdf')
Amit Developer- Atlantic 20 Reputation points

2025-05-05T15:05:17.2066667+00:00

I tried option 1. But again I got this error in log stream
2025-05-05T15:03:14.014528560Z /opt/startup/startup.sh: 23: /home/site/wwwroot/startup.sh: not found
Alekhya Vaddepally 1,670 Reputation points Microsoft External Staff Moderator

2025-05-05T15:42:25.8566667+00:00
Hi Amit Developer- Atlantic,

Ensure the correct file format and encoding

If you have created or edited Startup.Sh on Windows, change it to Unix (LF) line ending:

In the VS code, click on the right corner → CRLF →Change to LF

Or use dos2unix:

dos2unix startup.sh

Also make sure the file is:

UTF-8 encoded ,Has this shebang on the first line:

#!/bin/bash

Make sure the startup when you deploy. Your project route is in the directory. For example:

├── app.py ├── startup.sh ✅ ├── requirements.txt

Use your deployment method (FTP, GitHub Actions, Azure CLI, etc.) to redeploy the entire directory.

you can also setup up startup command in Azure portal

Go to your App Service ->Configuration > General Settings->Startup Command

/home/site/wwwroot/startup.sh

if you have any further concerns or queries, please feel free to reach out to us.
Amit Developer- Atlantic 20 Reputation points

2025-05-05T16:28:36.3466667+00:00

Plz check screenshots
Amit Developer- Atlantic 20 Reputation points

2025-05-06T06:50:59.8666667+00:00

Did you check the screenshots
Sampath 3,750 Reputation points Microsoft External Staff Moderator

2025-05-06T10:09:59.04+00:00

Hello @Amit Developer- Atlantic , could you please check your private messages and respond there?
Sampath 3,750 Reputation points Microsoft External Staff Moderator

2025-05-08T10:02:38.1733333+00:00

Hi Amit Developer- Atlantic, Let know if helped in comments
Amit Developer- Atlantic 20 Reputation points

2025-05-08T10:08:56.91+00:00

it worked ..thank you so much
Sampath 3,750 Reputation points Microsoft External Staff Moderator

2025-05-08T10:16:59.59+00:00

Hi Amit Developer- Atlantic, converting above comment into an answer, please click "Yes" and "accept" it. Thank you.

Accepted answer

0 additional answers

Your answer

Divyesh Govaerdhanan 6,400 Reputation points

2025-05-04T16:19:10.51+00:00

Hello,

Application error indicates the runtime error on your front-end application. You can check App Service logs to identify the error. Please check the below,

In App Service, Under Monitoring

Log stream → Real-time logs

Diagnose and solve problems → Quick insights on issues

Application Logs (if configured)

With detailed errors on the above monitoring options, you will be able to fix the application error in your application.

Please Upvote and accept the answer if it helps!!
Amit Developer- Atlantic 20 Reputation points

2025-05-05T09:59:58.79+00:00

How can I install wkhtmltopdf and use the path in my app.py code
Alekhya Vaddepally 1,670 Reputation points Microsoft External Staff Moderator

2025-05-05T10:38:48.83+00:00

Hi Amit Developer- Atlantic,

When you use wkhtmltopdf in your python app (often through libraries like PDFKIT), this requires Wkhtmltopdf binary to be installed and accessible from the system path. If the binary is missing or the path is not set correctly, the app will throw an error - which in the production environment, can only appear as a "app error" without a wide log.

Install wkhtmltopdf on the server:

If you are using Azure App Service (Linux or Windows), then you need to manually install wkhtmltopdf as it is not pre-installed by default.

For Linux app services, use a startup script to install it:

apt-get update apt-get install -y wkhtmltopdf

For Windows app services, it is more complex since installing a system-wide tool, not straightforward. You may need to include wkhtmltopdf binary in your project and call it using the absolute path.

Wkhtmltopdf

bundle in your app directory:

Download the binary from the official wkhtmltopdf site and include it in a folder (eg, bin/) in your project.

Update your app.py to use the right path:

Here is an example of how to clearly configure the path in Python:

import pdfkit config = pdfkit.configuration(wkhtmltopdf='/absolute/path/to/wkhtmltopdf') pdfkit.from_url('http://google.com', 'out.pdf', configuration=config)

Change '/absolute/path // wkhtmltopdf' with the actual path to your server or bundle location.

After deploying these changes, restart your app.

https://learn.microsoft.com/en-us/azure/app-service/configure-custom-container?pivots=container-linux&tabs=debian
https://learn.microsoft.com/en-us/azure/app-service/quickstart-python?tabs=flask%2Cwindows%2Cazure-cli%2Cazure-cli-deploy%2Cdeploy-instructions-azportal%2Cterminal-bash%2Cdeploy-instructions-zip-azcli
if you have any further concerns or queries, please feel free to reach out to us.
Amit Developer- Atlantic 20 Reputation points

2025-05-05T11:46:41.97+00:00

I am getting this error in bash
E: List directory /var/lib/apt/lists/partial is missing. - Acquire (13: Permission denied)

E: Could not open lock file /var/lib/dpkg/lock-frontend - open (13: Permission denied)

E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), are you root?
Alekhya Vaddepally 1,670 Reputation points Microsoft External Staff Moderator

2025-05-05T13:15:32.3233333+00:00

Hi Amit Developer- Atlantic,
You are getting many permission errors because the command you are running (such as APT-Get Update or APT-GET Install) requires root privileges, but the shell you are using (possibly your deployment or inside the Azure App service environment) is not root shell).

This is why you are seeing:

Not allowed permission

Are you root

To solve these permission issues, you have to prefix the command with the Sudo (if the sudo is available in your environment):

sudo apt-get update sudo apt-get install -y wkhtmltopdf

If you are running in restricted environment like Azure App Service (Linux), you may not have the use of Sudo. In such cases, the recommended approach is:

Create a file named startup.sh in your project directory with these contents:

#!/bin/bash apt-get update && apt-get install -y wkhtmltopdf gunicorn --bind=0.0.0.0 --timeout 600 app:app

Make it executable (if running locally):

chmod +x startup.sh

Configure your Azure App to use Custom Startup Command: Go to Azure Portal> App Services> Configuration> General Settings. Set Startup Command:

/home/site/wwwroot/startup.sh

Deploy your app with the startup.sh file included.
https://learn.microsoft.com/en-us/azure/app-service/configure-custom-container?pivots=container-linux&tabs=debian
https://learn.microsoft.com/en-us/azure/app-service/configure-language-python?pivots=python-framework-flask%2Cpython-3.9#customize-startup-command
Amit Developer- Atlantic 20 Reputation points

2025-05-05T13:42:09.6566667+00:00

Now i am getting this error
wkhtmltopdf exited with non-zero code 127. error: /tmp/8dd8bcfb4d3405c/bin/wkhtmltopdf: error while loading shared libraries: libjpeg.so.62: cannot open shared object file: No such file or directory
Alekhya Vaddepally 1,670 Reputation points Microsoft External Staff Moderator

2025-05-05T14:16:07.6966667+00:00

Hi Amit Developer- Atlantic,
Option1:Install Dependencies via Startup Script (Best for Azure App Service Linux)

Modify your startup.sh to install the missing dependencies before starting your app:

#!/bin/bash apt-get update && apt-get install -y \ libjpeg62-turbo \ libxrender1 \ libxext6 \ xfonts-base \ xfonts-75dpi \ wkhtmltopdf gunicorn --bind=0.0.0.0 --timeout 600 app:app

It installs Libjpeg62-Turbo, which provides Libjpeg.so.62. Also ensure that this is the script: Saved in his project directory, marked as executable, and Configured as a startup command in Azure.
https://learn.microsoft.com/en-us/azure/app-service/configure-custom-container?pivots=container-linux&tabs=debian
https://learn.microsoft.com/en-us/azure/app-service/overview#supported-linux-distributions
Option2:Use the fully bundled Wkhtmltopdf build (portable static version)

Download the static (self-contained) Linux Build of Wkhtmltopdf from his official site:

https://wkhtmltopdf.org/downloads.html

Use a version like wkhtmltox-0.12.6-1.alpine3.17_x86_64.apk.tar.gz or wkhtmltox-0.12.6-1-centos7-amd64.tar.xz

Remove it in your project (/bin) folder.
Update your Python code to use the bundled path:

import pdfkit config = pdfkit.configuration(wkhtmltopdf='/home/site/wwwroot/bin/wkhtmltopdf')
Amit Developer- Atlantic 20 Reputation points

2025-05-05T15:05:17.2066667+00:00

I tried option 1. But again I got this error in log stream
2025-05-05T15:03:14.014528560Z /opt/startup/startup.sh: 23: /home/site/wwwroot/startup.sh: not found
Alekhya Vaddepally 1,670 Reputation points Microsoft External Staff Moderator

2025-05-05T15:42:25.8566667+00:00

Hi Amit Developer- Atlantic,

Ensure the correct file format and encoding

If you have created or edited Startup.Sh on Windows, change it to Unix (LF) line ending:

In the VS code, click on the right corner → CRLF →Change to LF

Or use dos2unix:

dos2unix startup.sh

Also make sure the file is:

UTF-8 encoded ,Has this shebang on the first line:

#!/bin/bash

Make sure the startup when you deploy. Your project route is in the directory. For example:

├── app.py ├── startup.sh ✅ ├── requirements.txt

Use your deployment method (FTP, GitHub Actions, Azure CLI, etc.) to redeploy the entire directory.

you can also setup up startup command in Azure portal

Go to your App Service ->Configuration > General Settings->Startup Command

/home/site/wwwroot/startup.sh

if you have any further concerns or queries, please feel free to reach out to us.
Amit Developer- Atlantic 20 Reputation points

2025-05-05T16:28:36.3466667+00:00

Plz check screenshots
Amit Developer- Atlantic 20 Reputation points

2025-05-06T06:50:59.8666667+00:00

Did you check the screenshots
Sampath 3,750 Reputation points Microsoft External Staff Moderator

2025-05-06T10:09:59.04+00:00

Hello @Amit Developer- Atlantic , could you please check your private messages and respond there?
Sampath 3,750 Reputation points Microsoft External Staff Moderator

2025-05-08T10:02:38.1733333+00:00

Hi Amit Developer- Atlantic, Let know if helped in comments
Amit Developer- Atlantic 20 Reputation points

2025-05-08T10:08:56.91+00:00

it worked ..thank you so much
Sampath 3,750 Reputation points Microsoft External Staff Moderator

2025-05-08T10:16:59.59+00:00

Hi Amit Developer- Atlantic, converting above comment into an answer, please click "Yes" and "accept" it. Thank you.

Answer 1

Hi Amit Developer- Atlantic,

Create the startup script in your project directory. You can name it startup.sh.

Add your startup command inside the file. Below is sample Example for Flask with custom command:

gunicorn -b  0.0.0.0:8000  app:app

Commit the file to your code repository.

In the Azure Portal :

Go to your App Service → Configuration → General settings.
In Startup Command, enter: ./startup.sh
Click Save, then Continue when prompted to restart the service.

Please don’t forget to click "Accept the answer" and click "Yes" .So it can be helpful for others with similar questions.

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