Identity

Property	Value
Binary	`smartctl`
Config	`/etc/smartd.conf` (for the background monitoring daemon `smartd`)
Logs	Syslog / journald via `smartd`; self-test results stored on device
Type	CLI tool (part of smartmontools)
Install	`apt install smartmontools` / `dnf install smartmontools`

Key Operations

Task	Command
Overall health check (pass/fail summary)	`sudo smartctl -H /dev/sda`
All SMART attributes and device info	`sudo smartctl -a /dev/sda`
Device identity only (model, serial, firmware)	`sudo smartctl -i /dev/sda`
Start a short self-test (~2 minutes)	`sudo smartctl -t short /dev/sda`
Start a long self-test (hours, depends on size)	`sudo smartctl -t long /dev/sda`
Start a conveyance self-test (after shipping)	`sudo smartctl -t conveyance /dev/sda`
Check self-test log / results	`sudo smartctl -l selftest /dev/sda`
Check SMART error log	`sudo smartctl -l error /dev/sda`
Enable SMART on a drive	`sudo smartctl -s on /dev/sda`
NVMe drive health	`sudo smartctl -a --device=nvme /dev/nvme0`
USB drive via ATA passthrough	`sudo smartctl -a -d sat /dev/sdb`
USB drive with alternate passthrough	`sudo smartctl -a -d usb /dev/sdb`

ID	Attribute	Critical Threshold
5	Reallocated Sector Count	Any non-zero value is a warning; rising count indicates imminent failure
9	Power-On Hours	Context only; high hours on a used drive increases risk
187	Reported Uncorrectable Errors	Any non-zero value is serious
188	Command Timeout	Non-zero indicates bus or connector issues
196	Reallocation Event Count	Non-zero: sectors have been remapped
197	Current Pending Sector Count	Non-zero: sectors waiting to be reallocated; read errors occurring
198	Offline Uncorrectable Sectors	Non-zero: sectors that could not be recovered
199	UDMA CRC Error Count	Non-zero: cable or controller signal integrity issue

Symptom	Cause	Fix
`Smartctl open device: failed to open`	Requires root	Prefix with `sudo`
USB drive returns no SMART data	Enclosure does not pass SMART commands	Try `-d sat`, `-d usb`, or `-d sat,12`
"SMART support is: Unavailable"	Drive or firmware does not support SMART	Replace with a SMART-capable drive; no workaround
Overall health says PASSED but attribute 5 is rising	Overall PASSED is a conservative pass/fail; attributes tell the real story	Non-zero Reallocated Sector Count means the drive is degrading — schedule replacement
Self-test status shows "in progress"	Test runs in the background	Check again in a few minutes; `smartctl -a` shows percentage complete
NVMe shows different attribute names	NVMe uses a different SMART data structure	Use `--device=nvme`; attributes map to NVMe Log Page 0x02 fields

Status	Meaning
`Completed without error`	Test passed — no issues found
`Aborted by host`	Test was cancelled before completing
`Interrupted (host reset)`	System rebooted mid-test
`Fatal or unknown error`	Test itself failed — drive is suspect
`Completed: read failure`	Test found a read error at the logged LBA; sector is failing
`Self-test routine in progress`	Test is running; check again later

Root required: smartctl opens the raw device file, which requires root. Always use sudo.
USB enclosure passthrough: most USB-to-SATA bridge chips do not forward SMART commands by default. Try -d sat (SAT passthrough) or -d usb to work around this. Some cheap enclosures support no passthrough method at all.
Tests run in the background: starting a short or long test returns immediately. The test runs on the drive's internal controller. Check results with -l selftest or -a after waiting the estimated time (shown when the test starts).
"PASSED" does not mean healthy: the overall health check passes unless a SMART threshold has been crossed by the manufacturer's definition. A drive with dozens of reallocated sectors can still return PASSED. Always read the attribute table, specifically attributes 5, 187, 196, 197, and 198.
NVMe attribute names differ: NVMe uses a different log page structure than ATA SMART. Attribute names like "Available Spare" and "Percentage Used" replace the ATA numbering. Always include --device=nvme for NVMe drives.
smartd for ongoing monitoring: smartctl is a one-shot query tool. For continuous monitoring, configure smartd in /etc/smartd.conf to run scheduled self-tests and email alerts on threshold crossings.

See references/ for: