smartmontools 7.5

Drives usually report that they are failing before they fail. smartmontools is how you read that report.

Reading the attributes

sudo smartctl -a /dev/sda           # everything
sudo smartctl -H /dev/sda           # overall health assessment
sudo smartctl -a /dev/nvme0         # NVMe health log

The attributes that actually predict failure on a spinning disk:

• Reallocated_Sector_Ct, sectors remapped after failing. Non-zero and rising is the clearest warning.
• Current_Pending_Sector, sectors waiting to be remapped. Worse than reallocated.
• Offline_Uncorrectable, sectors that could not be read at all.

A drive passing the overall health assessment with rising pending sectors is a drive to replace. The PASSED result is a low bar.

On NVMe, watch percentage_used, available_spare, and media_errors. Our nvme-cli guide covers the NVMe-specific commands.

Self-tests

sudo smartctl -t short /dev/sda     # a couple of minutes
sudo smartctl -t long /dev/sda      # hours, reads the whole surface
sudo smartctl -l selftest /dev/sda  # results

The long test reads every sector, which is how latent bad sectors get found while you still have redundancy, rather than during a RAID rebuild when you do not.

The daemon is the point

Reading attributes manually means remembering to. smartd does it for you:

sudo systemctl enable --now smartd

# /etc/smartd.conf
DEVICESCAN -a -o on -S on -s (S/../.././02|L/../../6/03) -m you@example.com -M exec /usr/share/smartmontools/smartd-runner

That schedules a short test nightly at 02:00 and a long test Saturdays at 03:00, and emails on failure.

Send a test alert. An untested alerting path is not an alerting path:

sudo smartd -q onecheck

What SMART does not tell you

It is a useful signal and not a guarantee. Drives fail suddenly with clean SMART data, and drives with alarming attributes sometimes run for years.

Treat it as one input alongside real backups. Our smartctl guide covers reading the output properly.

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