How to list services with systemctl
List running, installed, enabled and failed Linux services with systemctl, then inspect one unit without confusing current state with boot configuration.
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Updated practical guides
Troubleshooting steps, examples and references. Each guide explains what was checked and where platform testing is still limited.
How to install Docker Engine on Ubuntu
Install Docker Engine from Docker’s signed APT repository on a supported Ubuntu release, verify the daemon and understand its access and firewall implications.
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How to install NVIDIA drivers on Ubuntu
Use Ubuntu’s recommended driver selection, reboot safely, verify with nvidia-smi and diagnose Secure Boot problems without adding an unnecessary PPA.
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How to clear the DNS cache on Ubuntu
Identify Ubuntu’s active resolver, flush systemd-resolved with resolvectl, check other caching services and verify the result.
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Fix “Unable to correct problems, you have held broken packages”
Diagnose Ubuntu dependency conflicts by checking holds, candidate versions, repositories and APT’s proposed solution before changing packages.
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Fix “Could not get lock /var/lib/dpkg/lock-frontend” in Ubuntu
Identify the process using the APT or dpkg lock, let legitimate updates finish and repair interrupted configuration without deleting lock files.
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Fix “Read-only file system” in Linux
Determine why Linux mounted a path read-only, distinguish an intentional mount from filesystem errors and choose a safe remount or offline repair.
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Fix “No space left on device” in Linux
Diagnose Linux storage errors with df, inode counts and deleted-open-file checks. Choose a targeted cleanup after identifying the failing filesystem.
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Fix “Unable to locate package” in Ubuntu
Check APT package names, repository updates, Ubuntu releases and CPU architecture before adding sources or changing installation methods.
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How to change your Ubuntu hostname and verify it
Change an Ubuntu hostname with hostnamectl, check local resolution and understand why DNS, cloud-init and container names need separate handling.
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How to install a .deb file in Ubuntu with APT
Inspect a local Debian package, preview the changes, install with APT and verify its package state. Diagnose dependency and architecture errors.
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Fix “Temporary failure in name resolution” in Ubuntu
Separate DNS lookup failures from network reachability. Inspect getent, routes, resolv.conf and systemd-resolved without overwriting managed settings.
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How to start Ubuntu from PowerShell with WSL
List installed WSL distributions and launch Ubuntu explicitly from PowerShell, including when Ubuntu is not the default distribution.
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Fix “not recognized as the name of a cmdlet” in PowerShell
Check spelling, command discovery, module availability and script paths before changing PowerShell execution policies.
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Does Bash have a goto command? Use functions and loops
Bash has no built-in goto statement. Replace labels with functions, loops, break, continue or return.
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How to go back in Bash: cd .. versus cd -
Move to the parent folder, return to the previous directory, or use pushd and popd for a directory stack.
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Bash permission denied: diagnose and fix script access
Fix Bash permission denied by checking the file, execute bit, parent directories and mount options. Follow a tested example before changing permissions.
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Bash command not found: check PATH, packages and scripts
Diagnose Bash command not found with command -v, type and PATH checks. Learn when to use ./ for a script and how to test a directory on PATH.
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Check Linux disk space with df and du
Check free filesystem space with df and directory usage with du. Compare their output, inspect inodes and understand why disk totals can disagree.
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systemctl command not found: identify your Linux environment
Fix systemctl command not found by checking PATH, your Linux distribution and PID 1. Distinguish a missing executable from systemd not running.
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How to enable SSH on Ubuntu and verify the connection
Install the Ubuntu OpenSSH server, inspect its service or socket, check access rules and verify a connection. Understand client versus server checks.
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How to enable dark mode in RStudio
Choose a dark editor theme in RStudio, make the surrounding interface match, and switch back if you prefer a light theme.
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How to keep PowerShell open after a script finishes
Run a script in an existing terminal, or use -NoExit when launching PowerShell. Understand when a prompt or transcript helps.
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Git Bash missing from the Windows right-click menu
Check Windows’ extended context menu and Git for Windows shell integration before changing settings or reinstalling.
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Python runs in the terminal but shows no output
Distinguish a silent script from the interactive prompt, an uncalled function, waiting input and buffered output.
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Fix “could not find part of the path” in PowerShell
Check the actual path, its parent folder and the working directory, using literal paths for filenames containing brackets.
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How to check your Azure login in PowerShell
Inspect your Az context, check token acquisition without printing secrets, and distinguish Azure PowerShell from Azure CLI.
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Set PowerShell execution policy for the current session
Inspect Windows execution policy and use an explicit scope when a trusted script requires a policy change.
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Where are PowerShell scripts located?
PowerShell scripts can be saved anywhere. Find a project script, identify the running script and inspect profile paths.
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How to exit Git Bash without losing your work
Save editor buffers, check repository status and running jobs, then exit. Closing a shell does not commit or stash files.
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Use Python 3.9 for a legacy project without removing Python 3.10
Keep system Python intact and isolate legacy dependencies. Python 3.9 is end of life and should not be the default for new work.
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Can Python use Greek letters in variable names?
Python supports many Unicode identifiers, including Greek letters, but its keywords and syntax are not translated.
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Why can’t Python find my file?
Print the current working directory and resolved path, then decide whether the file belongs beside the script or in the working folder.
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How to put an apostrophe in a Python string
Use double quotes around text containing an apostrophe, or escape a single quote with a backslash.
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How to exit Python interactive mode
Leave the Python prompt with quit() or an end-of-file shortcut, and distinguish the interpreter from your shell.
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Why is my CSS not being applied? A practical checklist
Check the stylesheet request, selector, declaration and cascade in that order. Use a minimal example to isolate the problem.
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Create a Python dictionary of student names and grades
Store grades by name, update a value, handle missing keys and calculate an average without failing on an empty dictionary.
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