df Command Reference: Flags, Usage & CI Examples

df reports free and used space on mounted filesystems.

df shows filesystem capacity and usage per mount point. In CI it is the go-to for diagnosing "No space left on device" failures on runners with limited disk.

Common flags and usage

• -h: human-readable sizes
• -i: inode usage instead of bytes
• -T: show the filesystem type
• --output=source,size,used,avail,pcent: choose columns
• df -h <path>: just the filesystem holding a path

Example

df -h /
df -i /   # check inode exhaustion, not just bytes

In CI

Run df -h before a large build or artifact download to confirm there is room, and again after a failure to confirm whether disk caused it. "No space left on device" can also be inode exhaustion (millions of small files), which only df -i reveals.

Key takeaways

• df -h shows free space per filesystem.
• "No space left" can be inode exhaustion, visible only with df -i.
• Check df before and after disk-heavy steps in CI.

Related guides