Read-only file system

All errors Free
Linux & shell

Read-only file system

A write was rejected because the filesystem is mounted read-only.

What it means

A write was rejected because the filesystem is mounted read-only.

Likely cause

The mount is intentionally read-only, or the kernel remounted it read-only after detecting filesystem errors.

How to fix it

Remount writable with "mount -o remount,rw <mountpoint>"; if it went read-only due to errors, unmount and repair it with "fsck" first.

Other Linux & shell errors

bash: command not found The shell could not locate an executable matching the command name you typed. Permission denied The operating system blocked the action because your user lacks the required permission on the file or resource. No such file or directory A referenced file or directory path does not exist on the filesystem. Segmentation fault (core dumped) A program crashed because it tried to access memory it is not allowed to touch, and a core dump was written. Killed (out of memory) The kernel's out-of-memory killer terminated the process because the system ran out of available memory. No space left on device A write failed because the target filesystem has no free space (or no free inodes) left. cannot execute binary file: Exec format error The kernel could not run the file because its binary format does not match the current CPU architecture or type. Too many open files A process hit the per-process limit on the number of simultaneously open file descriptors. bind: Address already in use A service could not bind to its network port because another process is already listening on it. ssh: connect to host port 22: Connection refused The SSH client reached the host but nothing accepted the connection on port 22. Host key verification failed SSH aborted because the host's presented key does not match the one stored in known_hosts. user is not in the sudoers file Your user is not authorized to run commands via sudo and the attempt was logged. bad interpreter: No such file or directory A script could not run because the interpreter named in its shebang line does not exist at that path. error while loading shared libraries The dynamic linker could not find or load a shared library (.so) that the program depends on. Broken pipe A process tried to write to a pipe or socket whose reading end has already been closed. Operation not permitted The kernel denied a privileged operation even though the file may be accessible, because it requires a capability you lack.

About Error Code Lookup

The Error Code Lookup is a searchable directory of more than 200 common error messages and codes across 12 categories: HTTP status codes, Windows error codes, browser and network errors, JavaScript, Python, PHP, Node.js and npm, Java, MySQL, Git, Linux shell errors and email/SMTP codes. Every entry is written in plain language for quick troubleshooting.

Each error is explained in three parts: what the message actually means, what usually causes it and concrete steps to fix it. That structure turns a cryptic string like ERR_CONNECTION_REFUSED or 0x80070005 into an actionable checklist instead of a guessing game.

You can filter the list by category, search by code, constant or message fragment, and copy any code with one click. Every error also has its own dedicated page with related errors from the same category, so you can bookmark or share a direct link to the exact fix.

How to use Error Code Lookup

  1. Type the error code or message into the search box — for example 404, ERR_NAME_NOT_RESOLVED or 0x80070005.
  2. Narrow the results with the category filter (HTTP, Windows, JavaScript, MySQL and so on) if the search returns too many entries.
  3. Open the matching entry to read what it means, its likely cause and how to fix it.
  4. Use the copy button to grab the exact code for a bug report or support ticket.
  5. Check the related errors section for other errors from the same category.

Frequently asked questions

It covers 12 categories: HTTP status codes, Windows system errors, browser and network errors, JavaScript, Python, PHP, Node.js and npm, Java, MySQL, Git, Linux shell errors and email/SMTP reply codes — more than 200 entries in total.

Search with fewer words. The shortest unique part works best: just the numeric code (“404”, “0x80070005”) or the constant name (“ERR_NAME_NOT_RESOLVED”) rather than the full sentence your system printed.

Yes. Each entry has a dedicated detail page explaining the meaning, likely cause and fix, plus related errors from the same category. You can bookmark it or send the link directly to a colleague or a support ticket.

The fixes describe the standard, widely accepted resolution for each error. Still, read the likely-cause section first — the same code can have several triggers, and matching the cause to your situation tells you which fix applies.

Yes, it is completely free. You can search, browse the category directory and open as many error detail pages as you need without an account.
Share this
Related Tools
Code Formatter Beautify HTML, CSS and JavaScript — re-indent and add line breaks to make messy or minified code readable. Free
Code Minifier Shrink HTML, CSS and JavaScript — strip comments and whitespace to make files smaller and load faster. Free
Array Formatter Expand inline arrays and objects onto clean indented lines, or collapse them back inline — for PHP, JavaScript, TypeScript, JSON, Python, Ruby and more. Free
Regex Tester Build, test and debug regular expressions live in your browser — instant match highlighting, capture groups, substitution preview, a plain-English explanation and ready-to-paste code for 15+ languages. Free
Cron Expression Builder Build a cron expression from a simple, visual form — set each field, see the live expression, human-readable schedule and next run times, then parse any expression back into the form. Free
JWT Decoder Decode a JWT header & payload (signature not verified). Free
Popular searches
error code lookup error message database what does this error mean windows error codes chrome error codes http error codes list fix error message error code meaning
Need help?
Found an issue with this tool? Let our team know.
Report an issue

Add this free tool to your own website — copy and paste the code below.