jason nano and using jason_clocks for the fan

As was mentioned in the last post, the fan is turned on via the jetson_clocks utility that’s part of the initial Ubuntu 18.04 installation. This capability is provided so that heat from the board can be quickly dumped when running it and the GPU under load.

What is jetson_clocks, you ask? Let’s do a quick rundown.

nvidia@jnano-01:~$ file `which jetson_clocks`
/usr/bin/jetson_clocks: Bourne-Again shell script, ASCII text executable
nvidia@jnano-01:~$ jetson_clocks
Error: Run this script(/usr/bin/jetson_clocks) as a root user
nvidia@jnano-01:~$ sudo jetson_clocks --help
Maximize jetson performance by setting static max frequency to CPU, GPU and EMC clocks.
jetson_clocks.sh [options]
  --show             display current settings
  --store [file]     store current settings to a file (default: ${HOME}/l4t_dfs.conf)
  --restore [file]   restore saved settings from a file (default: ${HOME}/l4t_dfs.conf)
  run jetson_clocks.sh without any option to set static max frequency to CPU, GPU and EMC clocks.

Not much to the script operationally, and in order to use it, even for help, you need to preface it with sudo. That can get quite annoying if you accept how this Ubuntu’s /etc/sudoers file is set up, so here’s how to fix this Ubuntu from asking for your password every time you invoke sudo. On the %sudo line, add NOPASSWD: to the line as shown:

# Allow members of group sudo to execute any command

If you’re new to Linux or uncomfortable in general with messing with such configurations, then leave it alone. I have fat-fingered NOPASSWD in the past and screwed up my ability to invoke sudo, which can be quite annoying if you don’t have root access.

With that out of the way, you’ll note that there’s four ways to invoke jetson_clocks. The most common way is without any command-line switches. That turns on the fan at full RPM, and will generate the most noise. Yes, the fan is very quiet, but in a quiet room you can still hear the white noise of the spinning fan. You can turn down the RPM by invoking –store and then –restore.

If you store with no other arguments then the text output is stored in ~/l4t_dfs.conf. That’s the good news. The bad news is that you had to use sudo to get that file, and the ownership is root. To change that to your regular ownership (nvidia in this example) you would need to invoke ‘sudo chown nivdia:nvidia l4t_dfs.conf’. I used the username nvidia in this example because that’s how I set up the initial account. You can call your initial login account ‘george’ or ‘ringo’ or whatever fits best for you. It’s that local username (and by the way, the group name as well) that you want to change ownership of that file to. Once it’s changed, open it up in an editor. I use vi/vim, but gedit is also provided. Whatever editor you want to use, open it up:


At the bottom of the file, on the line with target_pwn, the default is 255 when you save it. To change it to a more reasonable value, such as 128, simply do that and save it back out. Then execute ‘sudo jetson_clocks –restore’ and it will use that file to set the fan RPM to the lower value, which in this case is 1/2 what the maximum is. The fan will slowly slow down to the new value, and it will get very, very quiet.

Once again, note that restarting the Nano will stop the fan from spinning. You have to explicitly restart the fan.

jetson nano, baby steps

Ubuntu 18.04 desktop running on the Jetson Nano and LG 34UM61 monitor

I turned 66 earlier this month and in the process hit official retirement age. Guys who are rich enough usually go out and get something really blingy, like a new set of golf clubs or a deep sea fishing set, or something equally expensive and self-indulgent. Me, I went out and spent a whole $99 on the Jetson Nano. I figured if I was going to be “retired” then I’d go back in time and work with what got me started many decades ago, an embedded system. I started out as an electrical engineer and wrote assembly language drivers and test routines for embedded systems. As time went along, I drifted deeper into writing software as the hardware side of the business moved out of Atlanta and to places like Dallas and Silicon Valley. I never went with them because I’d traveled to those places and they weren’t as enjoyable as Atlanta and the South. And I can’t knock software development as it helped pay the bills and raise a family. Now I don’t need to do that anymore and I can go back and do what really scratches my intellectual itches.

This embedded system is a whole lot different, and a whole lot more powerful, than the embedded systems I stared with in the early 1980s. Everything about the Jetson Nano is incredibly advanced from the systems available in the 1980s, starting with the 64-bit quad core ARM processor to the 128 core nVidia graphics co-processor being used for machine learning. And all for a mere $99. And I mean that. The kind of processing power and hardware resources on this board would have ranged from outlandishly expensive to impossible to obtain.

The operating system that is available with this board, a targeted version of open source Ubuntu 18.04 LTS compiled for the ARM Cortex-A57, would have cost additional thousands and been closed source with an NDA to sign on top of that.

This $99 board is a remarkable bargain of a computer. I’ve read the reviews of frustrated users who gave it one star talk about how difficult it to set up and operate. So far my experience has been nearly 100% trouble free. I’ve had a few minor bumps, but it’s been after getting the OS up and running and configuring the system. Experiences so far with this board have been as satisfying, if more so, than all my experiences with the Raspberry Pi from 2 to 4.

Now that I’m “retired” I’ll be dabbling in the uses for this board, as well as with all the other little bits and bobs I’ve been collecting now for some number of years. I’ll be able to sit back and move at my own speed without having to put it aside because I needed to go to sleep and then into work the next morning. I’m an inveterate tinkerer, and Jetson Nano is the ultimate tinkerer’s tool and toy.