A Technical I.T./DevOps Blog
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”?”
Problem scenario
You cannot make changes to an /etc/fstab file. It is read only. What should you do?
Possible Solution #1
If your /etc/fstab file is messed up (through manual changes to it), and your system boots it as read only, can you run a command like this?
sudo mount -o remount,rw /dev/mapper/foobar /directory/to/be/mounted
If you run “sudo cat /etc/fstab” you will see lines like this:
/dev/mapper/foobar / ext4 defaults 1 1
(If you saw the above,
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Continue reading “How Do You Make Changes to an /etc/fstab File when It Is Read Only?”
Problem scenario
You think a website field for a password should allow a password to be pasted in. This could make the users not copy the password. Some hackers exploit memory/RAM. Should you avoid allowing a password to be pasted in?
Solution
Traditionally confirmation password fields did not allow pasting (with control-v) from the clipboard. Now NIST is saying you can do this: https://pages.nist.gov/800-63-FAQ/
Some people think it is not ideal to have sensitive information in RAM.
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Question
Sometimes a client attempts to connect to or use an application. Sometimes a Kubernetes Pod is being created and tries to pull down an image. Sometimes a network device tries to establish a connection to an endpoint. These attempts can initially fail. Retries can be attempted in rapid succession. To mitigate excessive attempts in a short amount of time (to not waste resources or cause a denial-of-service attack),
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Continue reading “How Are Backoff Strategies (with Client Retries) Helpful?”
Problem scenario
You want to run the puttygen command on a Linux server. (You tried yum and dnf commands to install putty, but they failed.) What do you do?
Solution
Prerequisites
i. These directions assume you have installed the C compiler. If you need assistance, see How Do You Install a C Compiler on Linux?
ii. These directions also assume you have the GTK library installed.
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Continue reading “How Do You Install the Putty Utility on a Linux Server?”
Problem scenario
You are modifying /etc/security/pwquality.conf. Is it a recommended practice to have no or few repeating characters with different classes of characters including lowercase, uppercase, numbers and special characters?
Solution
It can be counter productive to have very strong password requirements according to the NIST (https://pages.nist.gov/800-63-FAQ/).
If you are using Linux or Unix, NIST does suggest you use a crack library dictionary (per A-B10 from https://pages.nist.gov/800-63-FAQ/).
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Continue reading “Is It a Best/Recommended Practice to Enforce Complex Passwords?”
Problem scenario
You think that the users should not click the “make visible” option when entering a password. As an I.T. professional, you are not sure if this should be used or not. You read and think that it should not be used. Is it recommended that you have a practice of not letting the users make the password visible?
Solution
It is not clear.
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Problem scenario
You want to implement a secure protocol for authentication. You want there to be a password and a second factor of authentication. Can an email (being in possession of an inbox) be a factor in MFA?
Answer
Maybe.
No, according to NIST: https://pages.nist.gov/800-63-FAQ/
But many companies do use email as a factor in multi-factor authentication.
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One of the following apply to your situation:
Problem scenario #1
You are running a quotacheck command. You get this error:
quotacheck: Cannot guess format from filename on /dev/mapper/ubuntu–vg-ubuntu–lv. Please specify format on commandline.
quotacheck: Cannot find filesystem to check or filesystem not mounted with quota option.
What should you do?
or
Problem scenario #2
You try to run an edquota command,
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Problem scenario
You run a quota -au or quota -ag command to see the latest/up-to-date statistics. You see the number of blocks or inodes is discrepant with what is currently on your system for the user or group. You tried rebooting, but that did not help. How do you get the use blocks and used inodes to be updated with a quota command?
Possible Solution #1
Run a command like this:
sudo quotacheck -vug
If you think something is still misleading/inaccurate,
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Continue reading “How Do You Get quota Commands to Return Current Data?”