Bash Script CRLF Character Causing Hidden Syntax Errors
CRLF characters in a Bash script are, by definition, invisible in a normal text editor — the carriage return character doesn't display as anything visible,...
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Bash Script Syntax Error Near Unexpected Token `then` or `fi`
"Syntax error near unexpected token" for then or fi almost always means Bash's parser reached that keyword in a context where the surrounding if statement's...
Bash trap Command Not Catching SIGINT or SIGTERM in Subshells
A trap handler that works correctly in the main script but doesn't fire inside a subshell or background process is expected Bash behavior — signal handling in...
Linux "Cannot Open Display" Running GUI App Over SSH or in Cron
"Cannot open display" means a GUI application needs an X11 display to render into, but none is available in the current context — an SSH session without X11...
Linux Memory Leak Analysis: free -m High "Used" Memory vs Cached/Buffers
High "used" memory reported by free -m is very often not a leak at all — Linux deliberately uses available RAM for disk caching and buffers to improve...
Linux "No Space Left on Device" Caused by Unlinked Deleted Files Holding Disk Space
When a Linux disk reports full despite deleted files, the space is very often still held by a long-running service — like journald, a database, or a web server...
Linux Process Stuck in D State (Uninterruptible Sleep), How to Handle
A process stuck in D state (uninterruptible sleep) is waiting on a kernel-level operation, typically I/O — and critically, it genuinely cannot be killed with a...
Linux Swap Space Full: How to Clear Swap Without Rebooting Server
Full swap space can be cleared without a reboot by temporarily disabling and re-enabling it — this forces the kernel to move any swapped-out data back into...
Linux systemctl Service Stuck in "activating (start-exec)" State
A service permanently stuck showing "activating (start-exec)" means systemd is waiting for the service's start process to signal that it's fully ready, but...