A Technical I.T./DevOps Blog
Problem scenario
You run a command like this:
sudo openssl req -newkey rsa:2048 -nodes -keyout contint.key -x509 -days 9999 contint.crt
You get this as the output: “req: Use -help for summary.”
What should you do?
Possible Solution #1
Use the “-out” flag between “9999” and “contint.crt”.
Possible Solution #2
Do you have an extra “-new” flag in your command?
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Continue reading “How Do You Troubleshoot the Error “req: Use -help for summary”?”
Problem scenario
You failed to use visudo on a Red Hat or Debian distribution of Linux. You try to elevate your user to sudo and run a command but you get: “jdoe is not authorized to run that command as root.”
You forgot the root password. You cannot boot into rescue/recovery mode. How do you correct the /etc/sudoers file?
Solution
Run “pkexec” without quotes.
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Continue reading “How Do You Troubleshoot “jdoe is not authorized to run that command as root”?”
Question
You have a program with two (or three) variables, but no other data structures. What is the space complexity?
Answer
O(1). An algorithm, as long as the number of variables is fixed, can have 1,000 variables and be said to have O(1) space complexity. The source is here:
https://stackoverflow.com/questions/43260889/what-is-o1-space-complexity …
Continue reading “What Is The Space Complexity when There Are Two Variables in a Program?”
Problem
You connect a USB convertor (for a wired ethernet cable) to your Linux laptop. It isn’t working as a plug-and-play device. What could be wrong?
Solution
1. In the GUI on the Linux desktop, go to “Settings” or “Control Settings”. 2. Then go to “Network”.
3. Click a plus sign “+” (to add a new profile).
4. On the Identity tab,
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Continue reading “How Do You Get a USB-to-Ethernet Cable to Work with Linux?”
Problem scenario
You run a quota command. But you get “quota: Cannot open quotafile…” //aquota.group or //aquota.user … “Permission denied.”
What should you do?
Possible Solution #1
Maybe you do not have permissions. Can you run it with “sudo “?
If you run it with sudo and just see the quota governing the root user, then try running a command like this:
sudo quota -u jdoe
# Replace “jdoe” with the non-root user
You may want to find the relevant files with commands like this:
sudo find / -name aquota.group
sudo find / -name aquota.user
Possible Solution #2
This assumes you have the chattr utility installed;
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Problem scenario
You try to start the Apache Kafka service. You get this:
[2021-07-25 12:15:36,687] INFO [Group Metadata Manager on Broker 1]: Finished loading offsets from [__consumer_offsets,24] in 123456789 milliseconds.
GroupMetadataManager…Finished loading offsets and group metadata from __consumer_offsets…seconds spent in the scheduler. (kafka.coordinator.group.GroupMetadataManager)
It just hangs and will not progress. What do you do?
Solution
Whenever a command hangs that is supposed to start a service,
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Continue reading “How Do You Fix Apache Kafka when It Hangs?”
Problem scenario
You are curious why the odd versions of Ubuntu get so little attention. Why is this?
Answer
Even versions get long term support. If you are uncertain which version of Ubuntu to install, we recommend the highest even number release. As of February 2022, this is Ubuntu 22.x.
See this for more information: https://ubuntu.com/about/release-cycle
Be advised that odd versions will have an end of life that is sooner than the end of life for the previous even version.
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Continue reading “Why Are Ubuntu Versions (the Corresponding Integer Number Values) Usually Even?”
Problem scenario
You want to make a basic file system (e.g., ext4) on your Linux server. What should you do on your Debian/Ubuntu server?
Solution
Run these commands:
sudo fallocate -l 500M /mnt/new_thing
sudo mkfs.ext4 /mnt/new_thing …
Continue reading “How Do You Make a File System on an Existing Ubuntu/Debian Linux Server?”
Problem scenario
You run a command like edquota, but you get an error about not finding a quota file to work on or no file systems with a quota have been detected. Or maybe you ran a quotacheck command and got an error about not being able to guess a format from a filename.
What should you do?
Solution
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Problem scenario
In VirtualBox you are trying to boot a VM, but you get “failed unmounting /cdrom”. You see no option to unmount or remove the CD ROM. What should you do?
Possible Solution #1
Restart VirtualBox. Close it. Reopen it.
Possible Solution #2
Reboot the computer hosting/running VirtualBox.
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Continue reading “How Do You Troubleshoot a VirtualBox VM saying “failed unmounting /cdrom”?”