If you use a small PC as Home Server NAS with a attached USB Drive you perhaps remark that the drive ALWAYS spinning if the Samba Daemon is active.
I researched this behavior and found out that the Samba Deamon (smbd) locks the drive access via VFS to the Kernel for the Powermanagement Tools like hdparm
Workaround:
- Mount the USB Drive to /usb with „sudo mount -t ext4 /dev/sdc1 /usb“
- Create a virtual Path by „sudo mkdir /nas-share“ and create a bind mount by „sudo mount –bind /usb /nas-share“
- Now edit sudo nano /etc/samba/smb.conf and change the share path from /usb to /nas-share
[usb]
comment = usb-drive-nas
browseable = yes
valid users = linux-username
writeable = yes
create mode = 0600
directory mode = 0700
path = /nas-share
Background Info / The Problem:
The core issue is that Samba’s design can interfere with the Linux kernel’s power management and spindown timers. When Samba directly shares a device like a USB drive, it may keep a persistent connection or periodically perform filesystem checks that prevent the drive from being truly idle. Even if no one is actively accessing the share, Samba’s internal processes, such as browsing for shares or maintaining a connection, can cause activity on the drive. This continuous activity keeps the drive awake and spinning, which is not ideal for power consumption or drive longevity.
Why Bind Mounting Works
A bind mount effectively creates an alias or a separate path to the same filesystem. When Samba is configured to share this bind-mounted path instead of the raw USB device mount point, it changes how Samba interacts with the drive.
Abstraction Layer: The bind mount acts as a layer of abstraction. Samba is now operating on a local directory path, and its background processes may not be directly tied to the underlying USB device’s „in-use“ status in the same way.
Kernel Power Management: This allows the Linux kernel’s built-in power management to recognize the USB drive as idle when no actual data is being read or written, despite Samba’s presence. The system can then correctly initiate the spindown sequence based on its idle-timeout settings.
By using a bind mount, you’re decoupling Samba’s constant chatter from the direct status of the physical drive, allowing the system’s power-saving features to function as intended.