How do I check free disk space on the filesystem an application actually uses?
df reports filesystem capacity, not the raw size of every disk. Query the application’s actual data path so a separate mount or container volume is not overlooked. Free space on / does not help a database whose own filesystem is full.
Before you start
- An authorised SSH session on the Linux server.
Instructions
1. Inspect relevant filesystem capacity
Choose paths used by the affected application. The type column helps identify the filesystem, and human-readable sizes are convenient for an initial review.
df -hT / /var /homeRead available space and the mount target for each path. Several paths can resolve to the same filesystem, which is not extra capacity.
2. Map a specific application directory
Use an existing data path rather than assuming the installation directory and data directory share storage.
findmnt -T /var -o TARGET,SOURCE,FSTYPE,OPTIONSReplace /var with the verified application path. The result shows the backing mount and relevant options such as read-only state.
Check the result
- The capacity report is tied to the exact path where writes fail. Investigate inode limits, quotas and read-only state if free blocks remain available.
Troubleshooting
- The provider disk size is larger than df shows
- The partition, logical volume or filesystem may not use all available block capacity. Inspect the full storage stack before any resize.
- df is slow on one path
- A remote or unhealthy mount may be delaying the query. Avoid repeatedly scanning every mount without identifying the affected one.
Official references
Use the documentation for your installed version when a flag, service name or platform feature differs.