Questions
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Solved: Unable to configure RSA server private key
This problem may occur if the private key and certificate do not match.
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.
How to Run a Docker Image as a Container?
Docker runs processes in isolated containers. A container is a process that runs on a host. The host may be local or remote. When an operator executes docker run, the container process that ru...
How to Remove Old and Unused Docker Images?
Since the docker version 1.13 you can use the docker prune command to remove all dangling data such as containers stopped, volumes without containers, and images with no containers. To remove dangl...
How to Remove Old Docker Containers?
You may have found docker rm command to remove a docker container. However, this works only for a single container and it would be very painful to run this command for every non-running docker cont...
How Do I Pass Environment Variables to Docker Containers?
It is always a good practice to separate the app from its configuration. It is not a good idea to have a database login credential defined as variables in the code of the application. This is why w...
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).
How to Mount a Host Directory in a Docker Container?
If you want to mound a host directory in a Docker container, you have to main ways to do that: Using the ADD command: The simplest way is to use the dockers ADD command as shown below: ADD . /path/...
How to List Containers in Docker?
Running containers If you want to list all the running docker containers, you can use the docker container ls command, which takes the following form: docker container ls This command is valid on a...
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: The Input Device Is Not a TTY
If you try to execute a command inside the docker using the Jenkins or jus try to use the -it option in the docker run command, you will get the following error: the input device is not a TTY How t...
How to Include Files outside of Docker’s Build Context?
You may have ended up in a situation where you wanted to include a file from outside of Docker's build context using the ADD command, but the ADD command requires the path to be within the build co...
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 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 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 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, 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 Remove a Docker Image?
To remove one or more specific images, you can use the docker rmi command. How to list all images If you want to list all the images before removing any, you can do they by running the following co...
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 Deal With Persistent Storage (e.g. Databases) In Docker?
The best way to deal with persistent data storage (such as a database) in Docker is to use Docker’s volume API (for docker 1.9.0 or newer) or use data-only containers for older versions of Docker. ...
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.
How to list all available CA SSL certificates on Ubuntu?
To list all available CA SSL certificates run the following lines of code:
How Do I Get into a Docker Container’s Shell?
If you want to explore containers file system it simply wan to get an access to containers shell, you can use one of the following options Using the docker exec command Docker version 1.3 or newer ...
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 Execute Multiple Commands in Docker-Compose?
It is possible to define and run multiple commands in the docker-compose.yml file. To execute multiple commands using Docker-Compose, structure the file in the following way: ... services: app: ...
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
Docker How to Change Repository Name or Rename Image?
Docker image Docker image name and tag are just an alias to a docker image id that looks similar to this d583c3ac45fd. If you want to change the name, run the following command: docker image tag ol...
How to Get a Docker Container’s Ip Address from the Host?
By default, the container is assigned an IP address for every Docker network it connects to. And each network is created with a default subnet mask, using it as a pool, later on, to give away the I...
How to Force Docker to Clean Build an Image?
When executing docker pull or docker run command, the daemon first checks for a similar image in the local machine by comparing the digests of the image. If it finds a match, the daemon simply crea...
How to Fix Docker Permission Denied Issue?
If you are struggling with the Docker permission denied error, we have prepared a quick fix for you. Step 1 - Create a docker group The first step is you create a docker group if you haven’t done i...
How to Explore Docker Container’s File System?
If you want to explore the Docker container’s file system, you can use on of the following methods. Using the docker exec command Docker version 1.3 or newer supports the docker exec command. This ...
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.
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.
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 ...
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.
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...