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jeff1evesque / raspberry-pi

Raspberry Pi connects ZigBee wireless devices to an apache server.
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Documentation: Adjust 'Configuration' Subsection #37

Closed jeff1evesque closed 9 years ago

jeff1evesque commented 9 years ago

We will change the USB System Partition subsection:

...
$ diskutil unmountDisk /dev/disk4
...

to the following:

...
$ sudo diskutil unmountDisk /dev/disk4
...

Otherwise, when issuing the command:

$ sudo dd if=2014-09-09-wheezy-raspbian.img | sudo pv | sudo dd of=/dev/rdisk4s1 bs=1m

will request for three passwords:

$ sudo dd if=2014-09-09-wheezy-raspbian.img | sudo pv | sudo dd of=/dev/rdisk1 bs=1m
Password:Password:Password:

Also, we will make a note that an SD card with the capacity of 48MiB/s will write the raspbian image at a transfer rate of about 12.6MiB/s:

$ sudo dd if=2014-09-09-wheezy-raspbian.img | sudo pv | sudo dd of=/dev/rdisk1 bs=1m
6400000+0 records in6MiB/s] [                                                             <=>   ]
6400000+0 records out
3276800000 bytes transferred in 248.722375 secs (13174528 bytes/sec)
3.05GiB 0:04:08 [12.6MiB/s] [                                                              <=>  ]
0+50020 records in
0+50020 records out
3276800000 bytes transferred in 248.744377 secs (13173363 bytes/sec)

which is more than 2x faster than our previous SD card (Dane-Elec Class 4, which means minimum write of 4MiB/s).

jeff1evesque commented 9 years ago

We need to adjust the following typo contained within the SD Boot Partition documentation subsection:

... Note: dd may take up to 20mins, with pv displaying a transfer rate between 3.9-5.23MiB/s. For example, when using Dane-Elec (Class 4), the transfer rate is about 11 minutes. This is reasonable, since the SD card is rated at a minimum write of 4MiB/s. However, a SanDisk with 48MiB/s capacity would write the Raspbian image in roughly 4 minutes (as shown above). ...

to the following:

... Note: dd may take up to 20mins, with pv displaying a transfer rate between 3.9-5.23MiB/s. For example, when using Dane-Elec (Class 4), the transfer time is about 11 minutes. This is reasonable, since the SD card expected to have a minimum transfer rate of 4MiB/s. However, an SanDisk with 48MiB/s capacity would write the Raspbian image in roughly 4 minutes (as shown above). ...