Questions
Find answers to frequently asked development questions. For information about Better Stack products, explore our docs.
How Do I Edit a File inside a Docker Container?
If you want to edit a file inside a docker container, you can follow these steps: 1. Find the id of the container To find the id of the running container, you can use the following command: docker ...
What Is the Difference between the ‘COPY’ and ‘ADD’ Commands in a Dockerfile?
When creating a Docker file, you may need to transfer some files from the host system to the docker image. Those files may be for example libraries or any other files that your application may need...
What Is the Difference between a Docker Image and a Container?
Docker image A Docker image ****is an immutable (unchangeable) file that contains the source code, libraries, dependencies, tools, and other files needed for an application to run. Sometimes t...
What Is the Difference between Docker-Compose Ports and Expose?
You may have wondered what is the difference between docker-compose ports and docker-compose expose. Here is a clear explanation to help you better understand the matter. Ports Ports mentioned in t...
What Is the Difference between CMD and ENTRYPOINT in a Dockerfile?
There is a big confusion around similarity and lack of clarity in the difference between the CMD and ENTRYPOINT instruction in Docker. Let’s clear things up. See the example Let’s say we want to cr...
How to Delete All Local Docker Images?
If you have a large number of docker containers and images, you can remove them all at once. Remove all docker images To delete all docker images, run the docker rmi command: docker rmi -f $(docker...
How to Copy Files from Host to Docker Container?
When creating a docker image, you may want to copy some files from the host machine to the docker image. These files may be native libraries, configuration files, or any other files that will be ne...
How to Copy Files from Docker Container to Host?
Before Docker 1.8, we could only copy files from the container to the host. However, as containers became even more popular, copying files to and from containers has become necessary. One of the re...
How to Copy Docker Images from One Host to Another without Using a Repository
There is an easy way to transfer Docker images from one host to another without using any repository. Copy Docker images from one host to another First, you need to save the docker image as a tar: ...
How to Connect to the Localhost of the Machine from inside of a Docker Container?
If you are running some kind of a server or any other service (such as a database) on localhost and the service isn’t exposing any port, you may have found yourself wondering how to connect to this...
How To Whitelist Better Stack IPs on Google Cloud Platform
Learn how to whitelist Better Stack IPs on Google Cloud and prevent any false incident alerting.
How To Whitelist Better Stack IPs on Azure
Learn how to whitelist Better Stack IPs on Microsoft Azure and prevent any false incident alerting.
How To Whitelist Better Stack IPs on AWS
Learn how to whitelist Better Stack IPs on AWS and prevent any false incident alerting.
How To Whitelist an Email Address in Microsoft Outlook
Learn how to whitelist an email address in Outlook via adding to contact book and creating a filter.
How To Whitelist an Email Address in Gmail
Learn how to whitelist an email address in Gmail via adding to contact book and creating a filter.
How to view and read cron logs on Ubuntu, Debian and CentOS?
Cron can generate logs, which are very useful in troubleshooting your cron jobs. In this quick tutorial, we will take a look at cron logs – how to find them and how to read them.
How to start logging cron job output to syslog on Ubuntu 20.04?
In this quick tutorial, we will take a look at how to redirect output from cron jobs to the main system log.
How to set up a cron job for a specific time and date?
In this quick tutorial, we will take a look at how to set up a cron job to run at a specific time.
How to setup cron job for automatic Let's Encrypt renewal?
Cron is a command-line job scheduler on Unix-like systems. It allows you to run automated tasks in the background and it's especially useful for repetitive jobs.
How to list and view all current cron jobs?
Cron is a command-line job scheduler on Unix-like systems. It allows you to run automated tasks in the background and it's especially useful for repetitive jobs.
Solved: Unable to configure RSA server private key
This problem may occur if the private key and certificate do not match.
Solved: Invalid command ‘SSLEngine
This frequently happens on fresh Apache servers. When Apache starts it reads through the configuration files. When it encounters `SSLEngine` directive, it considers it as unknown. This is caused by the fact that the server’s basic configuration does not have `mod_ssl` module installed or enabled.
Solved: Error 526 Invalid SSL Certificate
Error 526 indicates Cloudflare is unable to successfully validate the SSL certificate on the origin web server and the SSL setting in the Cloudflare SSL/TLS app is set to Full SSL (Strict) for the website.
Solved: Error:0D0680A8 : asn1 encoding routines: ASN1_CHECK_TLEN: wrong tag
This error is due to an invalid certificate format installed on the Apache webserver.
Solved: ERR_SSL_VERSION_OR_CIPHER_MISMATCH
When you are accessing the HTTPS secured website a series of steps is taken in the background to ensure that the connection is safe and trusted. Some of these steps consist of checking certificates. If the browser does not believe that the connection would be secure it displays this error.
Solved: curl: (35) ssl connect error
The main course of this problem is the outdated `curl` package on your system.
Solved: SSL_Error_rx_record_too_long
The usual cause is that the implementation of SSL on your server is not correct. The error is usually caused by a server-side problem which the server administrator will need to investigate.
SSL Certificate Problem: Unable to get Local Issuer Certificate
If you get SSL certificate problem: unable to get local issuer certificate error, it's an indication that your root and intermediate certificates on the system are not working correctly or not set up correctly.
Solved: NET::ERR_CERT_COMMON_NAME_INVALID
A NET::ERR_CERT_COMMON_NAME_IN error occurs when the domain the SSL certificate is installed on is not listed on the certificate (either as the common name, subject alternative name or covered by a wildcard).
Where to keep SSL certificates and private keys on Ubuntu and Debian?
To list all available CA SSL certificates run the following lines of code:
How to verify SSL certificates on the command line?
To validate an SSL certificate you can use one of the following approaches, depending on the type of the certificate.
How to save cron job output to file?
Any cron job can generate output. It may be log or error messages. Regardless of the nature of the output, you may want to save this output to a file. This can be done using the `>` operator.
How to run cron jobs every 5, 10, or 30 seconds?
By default, cron checks crontabs for cronjobs every minute. If you want to run a job every n seconds you need to use a simple workaround.
How to run cron jobs every 5, 10, 15 or 30 minutes?
Every minute cron goes through all the crontabs and looks for the jobs that should be executed. The exact time of the execution can be specified using the cron syntax. Whenever the parameter matches the current date and time cron job is executed.
How to run a cronjob as a specific user?
One of the features of Cron is the ability to run Cron jobs as a specific user. Sometimes you may even want to create a special user with limited privileges just to run Cron jobs. There are two methods how to run cronjob as a specific user.
How to prevent duplicate cron jobs from running?
Sometimes you may find that duplicate cronjobs are running at the same time. This may happen when the cronjob takes longer to complete than its execution interval. Here is a simple way to prevent this from happening ever again.
How to list all available CA SSL certificates on Ubuntu?
To list all available CA SSL certificates run the following lines of code:
How to get cron job errors in email with MAILTO?
One of the neat features of Cron is the ability to send emails when an error occurs during the execution of the cronjob. This can be done using the `MAILTO` environmental variable. When executing cronjob, any output is mailed to the owner of the crontab or to the user or email address specified in the `MAILTO` environment variable in the crontab, if such exists.
How to generate a private key for the existing .crt file on Nginx?
Unfortunately, this is not possible. You cannot generate a private key out of an existing certificate. If it would be possible, you would be able to impersonate virtually any HTTPS webserver.
How to generate a private key for the existing .crt file on Apache?
Unfortunately, this is not possible. You cannot generate a private key out of an existing certificate. If it would be possible, you would be able to impersonate virtually any HTTPS webserver.
How to display remote SSL certificate details with CLI tools/cURL?
You can use `openssl` command like this. Replace the highlighted part with the select domain name
Solved: Errors in crontab file, can't install
You may encounter this error while creating a new crontab or updating an existing one that has a syntax error.
Does each subdomain need its own SSL certificate?
This depends purely on what type of certificate you have. You can have a standard single domain certificate. Aside from that, you can also get two following types of certificates.
Solved: Crontab bad minute error
Cron reads every line of the crontab. If the line is not a comment or an environmental variable, cron expects a correct and valid minute expression of the cronjob. If there is an invalid minute expression (e.g. a typo), cron will throw a **Bad minute error**.
Solved: Cron missing newline before EOF
This error may also happen when a crontab file is generated automatically and the generator failed to insert a newline character at the end of the crontab file.
Solved: (cron) info (No MTA installed, discarding output) error
If you get *SSL certificate problem: unable to get local issuer certificate* error, it's an indication that your root and intermediate certificates on the system are not working correctly or not set up correctly.
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