What Happens When Unrar Exceeds Disk Quota

When the unrar utility attempts to extract an archive that exceeds a user's disk quota, the extraction process halts immediately with a write error, leaving an incomplete, corrupted file on the filesystem and returning a non-zero exit status. This article explains the technical failure mechanism during the extraction, the expected error messages, the resulting state of the target files, and how to resolve the error.

The System-Level Failure Mechanism

Disk quotas on Unix and Linux systems are enforced at the kernel level. As unrar extracts compressed data, it decompresses the stream in memory and writes it to the storage device in sequential chunks.

When the written data causes the user's allocated block usage to cross the hard quota limit (or exceed the soft quota after the grace period expires), the operating system's write() system call fails. The kernel returns the standard EDQUOT (Disk quota exceeded) error code to the unrar process.

Error Messages and Exit Codes

Upon receiving the EDQUOT signal from the operating system, unrar cannot continue writing to disk. The command-line utility aborts the operation and outputs an error to the standard error (stderr) stream, typically formatted as:

Extracting  filename.ext                     Failed
Write error: Disk quota exceeded
Cannot create filename.ext
Total errors: 1

Depending on your distribution and version of RAR/UNRAR, the message might also state Write error: no space left on device. Once terminated, the utility exits with a non-zero status code (typically exit code 9 for a create error or exit code 1 for a general fatal error), which interrupts any automated bash scripts or background tasks relying on a successful return code (0).

The State of the Extracted Files

When unrar crashes due to a quota limit, it does not cleanly roll back changes by default:

  • Incomplete Target File: The file currently being written remains on the disk, truncated at the exact byte where the quota was hit. This file is incomplete, corrupted, and unusable.
  • Previously Extracted Files: Any files from the archive that were fully decompressed before the quota was reached will remain intact in the destination directory.
  • Subsequent Files: Any files queued after the failed file inside the archive will not be processed at all.
  • Persistent Quota Exhaustion: Because the truncated file and previously extracted files remain on the drive, the user's quota remains at 100% capacity, blocking other programs from writing temporary data, configuration files, or logs.

How to Resolve the Error

To recover from a failed extraction caused by an exceeded disk quota:

  1. Identify Usage: Run quota -s or quota -v to confirm current block limits and usage.
  2. Remove Corrupted Data: Delete the partially extracted file and any unwanted extracted contents using rm to free up immediate space.
  3. Redirect Extraction: If your quota on the target partition cannot be increased by a system administrator, extract the archive to a directory residing on an unconstrained mount point or external volume using the target path argument: 
    unrar x archive.rar /path/to/alternative/storage/