Without further explanation

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parted -a optimal /dev/sda
unit MiB
print free

#    Number  Start     End        Size       Type     File system     Flags
#            0,03MiB   1,00MiB    0,97MiB             Free Space
#     1      1,00MiB   1025MiB    1024MiB    primary  ext4            boot
#     2      1025MiB   5121MiB    4096MiB    primary  linux-swap(v1)
#     3      5121MiB   70657MiB   65536MiB   primary  ext4
#            70657MiB  476940MiB  406283MiB           Free Space

To display Content-Type correctly, you need to add the following values ​​to mime.types
otherwise the default_type application/octet-stream; directive will be used.

Setting minimum and maximum speeds for devices

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# 70000 kilobytes/s ~ 68 Mb/s
echo "70000" > /proc/sys/dev/raid/speed_limit_min
echo "100000" > /proc/sys/dev/raid/speed_limit_max

sysctl analogue

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dev.raid.speed_limit_min=70000
dev.raid.speed_limit_max=100000

What did the embedded system look like?

There is one small CubieBoard 2 next to the small router.
And there is no physical access to them.
A USB-UART is connected to a router controlled by LEDE, the pins of which are connected to CubieBoard2.
Both the router and CubieBoard2 are accessible via ssh.

It was the presence of UART in the assembly that allowed us to raise the fallen CubieBoard2 remotely.

How did it fail?

One day a regular update of the Debian kernel arrives
linux-image-4.9.0-8-armmp-lpae.
After the update the system stops responding.

How is this usually done?

Everything is simple here, you take out the microsd card, and then there is no need to describe it further.