Fix a permission error

Get past a Permission denied error from the CLI. The message itself carries what you need: what was refused, who owns it, and who asked - File permissions explains the format and when the checks run.

error: i/o error: cannot open `/roms/game.iso`: Permission denied (os error 13)
(`/roms/game.iso` is mode 0600 owned by 0:0; this process runs as 1000:1000)

Match your situation:

• Reading someone else's files. sudo chown them, add yourself to the owning group, or copy them somewhere you own.
• Writing to a read-only location. Point --output at a directory you own. rom-weaver creates missing output directories but never changes permissions on an existing one.
• Output files owned by the wrong user. New files inherit your identity and umask; rom-weaver does not copy the source file's mode.
• Inside a container. The message adds a container hint, because the usual cause is a uid mismatch against a bind mount. Re-run with --user "$(id -u):$(id -g)" as shown in Run in Docker.