post on RPi

44d6f2b9 · Murukesh Mohanan · bed94f48 · 44d6f2b9 · 44d6f2b9 · 44d6f2b9
Commit 44d6f2b9 authored Jun 30, 2019 by Murukesh Mohanan
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--- a/_posts/2019-06-30-poking-pi.md
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+---
+layout: post
+title: Poking around a Pi&colon; Part I
+tags: [tech, linux]
+---
+
+Over a year ago, I got a [Raspberry Pi 3B][amazon]. Yahoo! JAPAN has this nice
+system called [TechUP] for buying stuff (gadgets, books, subscriptions, etc.) to
+improve your technical skills. A Pi is perfect --- it's well within the budget,
+and you have lots of people using it for various projects, so there's a lot of
+material online that you can learn from. And the models are always increasing in
+power --- just look at the recently released Pi 4: a max of 4 GB of RAM
+(potentially more), USB 3, and Gigabit Ethernet that doesn't share buses with
+the USB ports. Today, though, I'll be talking about the Pi 3B and my experiments
+with it.
+
+It spent nearly a month collecting dust before I finally got around to booting
+it. And when I did upgrade from polygonal tuits, I was faced with a tough
+problem: which OS do I use?
+
+1. Raspbian is pretty popular, and perhaps the first among equals. But: Stable
+   releases of Debian-based distros like Raspbian tend to be heavily outdated.
+   One of my goals with the Pi was to play with new software.
+   I could hunt down repositories, or build stuff myself, but ¯\\\_(ツ)\_/¯
+2. Ubuntu's main repositories don't support ARM. That's over on
+   <http://ports.ubuntu.com/>. Even so, support in PPAs for ARM isn't that
+   widespread.
+3. Arch officially only supports the amd64/x86-64 architecture (they [dropped
+   support for i686][arch-i686] some time ago). [ARM], like i686, is supported
+   by the community. [Mirrors] are a bit of a problem. There are none in Japan.
+
+Instead of going for Raspbian or Ubuntu, I opted for installing Arch Linux.  I
+ended up picking Arch because it is my daily driver on my PC, and I already have
+a box running Ubuntu serving as a … server. It was time to see how Arch would
+hold up.
+
+<!-- section -->
+
+## Installation
+
+It's been over a year since I installed it, so I don't remember specifics of any
+problems I had during the installation. I don't think I had many --- except maybe
+~~if~~ when I goofed up with some commands. I did have some concern that the
+ARMv7 build that Arch Linux ARM recommended wouldn't be good enough, but I think
+things have mostly turned out just fine.
+
+Ah, yes! Like an idiot, I tried my default way of booting for system
+installations: using an USB drive. And was greeted with a blank screen. I think
+fiddled with the KVM switch, connecting everything to the Pi instead of the
+switch, I even tried flashing the disk a couple of times. Finally I Googled and
+realized that a Pi does not boot from an USB drive unless [it has been
+configured to do so][usb-boot] --- *by booting from a microSD card.* That meant
+buying one, and waiting a couple of days for its arrival.  Booting from the card
+went fine: I finally saw the rainbow splash. (All told, it was about 6 weeks
+since I bought the Pi that I first successfully booted it. Damn I'm lazy.)
+
+As I said before, Arch Linux itself worked pretty fine. I'd give it a Gold
+rating (not Platinum), because I have a had the occasional kernel panics over
+the past year, about once every couple of months or so. For the moment, I have
+stuck the `panic=10` bandaid on it.
+
+The main issue --- I can't even really call it an issue --- is that the
+community's preferred kernel is a bit old.  They track an LTS kernel, something
+to do with custom firmware needed for some components. Since I don't use most of
+it --- not the camera input, not the audio out, I don't even run a GUI on it ---
+I think I could get away with running the latest, mainline kernel. Something to
+test soon.  Shortly after I got the Pi, I wanted to try [iwd], the new wireless
+network management daemon. However, the kernel in use then (4.12-ish, I think)
+didn't support it. The kernel is currently 4.19 (following Arch's `linux-lts`),
+where my PC runs 5.1. I think it does support iwd now, but I haven't gotten
+around to testing it yet.
+
+<!-- section -->
+
+## Using a microSD card
+
+Since I had to boot from a card anyway, I decided to go with it completely,
+instead of configuring USB boot. This proved to be a mistake. I don't know if it
+was the card I'd bought (a [Toshiba M203][toshiba]) or something with the Pi's
+I/O, but damn, the system was slow. Tab completion, listing files, running
+commands --- everything had a very noticeable, multi-second  delay. I mean, I
+understand that the ARM CPU isn't comparable to the i7 on my PC, but this was
+slower than anything I'd used in the past decade, except for SSH connections over
+mobile internet. I thought it might be the CPU, but later, I realized it was the
+I/O from the card, when I attached a USB hard disk to it. Listing files on the
+disk was noticeably faster than doing so on the card. Then I noticed that
+essentially anything which touched the card turned slow, like it was nearing the
+accretion disk of a black hole. I decided to stick with the card for the time
+being, but it did lead to a lot of frustration.
+
+I finally moved to a USB flash drive a couple of weeks ago, and things have
+drastically improved. I couldn't use my 8GB drive - it turned out to be just
+a bit smaller than the 8GB microSD card. I could resize the partitions and all
+that, but meh … I did have another 16GB one lying around. That one worked OK. I
+had moved some stuff from the card to the hard drive for performance, but now I
+have I moved them back to the flash drive, simplifying my setup.
+
+<!-- section -->
+
+## Power
+
+I have a power strip with a couple of USB ports for charging, and I used one of
+those for powering the Pi. And so I have had warnings about "under voltage"
+pretty much from day zero. Even if I did buy a dedicated power adaptor for the
+Pi, I didn't have spare slots on the power strip. I tried changing cables, using
+shorter cables, etc. to no avail. I don't know if the under-voltage situations had any really impact on anything.
+They always seemed to be resolved in seconds, and I didn't notice any relation
+between their appearance and the aforementioned slow I/O. The one problem that
+might be linked to it was a hard disk acting up.
+
+I had two USB hard disks connected to the Pi, and the older one of them, a
+Toshiba Canvio bought in May 2012, started having problems.  It would randomly
+stop responding.  It could be the age of the drive, it could be the power ---
+I'm not sure. IIRC a consumer hard disk lasts around 5 years, so this one had
+already gone above and beyond. I managed to get all useful data off via my PC,
+though, which is why I doubt if it was really failing. I had another aged disk
+fail on an unrelated system around the same time, and that one just started
+spewing I/O errors all over the place (couldn't even copy data reliably off it).
+Or maybe I just experienced two failure modes of aging disks.
+
+I decided to bite the bullet and get a dedicated power supply, but I didn't feel
+like getting just power supply for the Pi. If I was going to have to mess with
+my current power setup, doing it just for the Pi felt like a waste. Instead,
+I got [a powered USB hub][hub] a few weeks ago, which also had an additional
+port for USB charging. I moved all the peripherals to it (except the flash drive
+used to boot it) and used it to power the Pi as well. I haven't had an
+under-voltage situation since.
+
+<!-- section -->
+
+## What next?
+
+So, what did I do with this Pi? I'll talk about the specifics in my next post.
+But the tl;dr is this: I configured it to run Nextcloud, and in general function
+as a file server with data on the hard disk.
+
+It also serves as the gateway to my home. I have set up SSH (with only
+public-key authentication allowed) and port-forwarded it over my router, so I
+can access the Pi, and by extension (with some help from Wake-on-LAN) my PC as
+well. A non-default SSH port means I don't see ~~many~~ any bots knocking on the
+SSH door.
+
+Overall, I'm pretty happy with the Pi. I'd like to upgrade to the Pi 4, mainly
+for USB 3 and Gigabit networking, but I can live with the current performance.
+The main bottleneck is my Internet (upload bandwidth a measly 10 Mbps), and
+there's nothing that upgrading will *really* improve. I'd even say the Pi is
+underutilized --- I'm barely using 200MB of RAM most of time, and the CPU's
+mostly idle too. I'd say if you don't have 4K media, a Pi 3B is a perfectly fine
+media server.
+
+[amazon]: https://www.amazon.co.jp/dp/B01CHJRAOK/ref=cm_sw_r_tw_dp_U_x_XnOcDb1XCNV0H "Amazon Japan link"
+[arch-i686]: https://www.archlinux.org/news/the-end-of-i686-support/
+[ARM]: https://archlinuxarm.org/
+[Mirrors]: https://archlinuxarm.org/about/mirrors
+[TechUP]: https://linotice.tumblr.com/post/180646706959/20181130
+[usb-boot]: https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/msd.md
+[toshiba]: https://store.shopping.yahoo.co.jp/jnh/TO3307M302EA.html
+[hub]: https://www.amazon.co.jp/gp/product/B07PD1ZVLY/
+[iwd]: https://lwn.net/Articles/770991/
--- a/cv.md
+++ b/cv.md
@@ -18,7 +18,7 @@ description: What have I been upto?
 - Mentored Yahoo! Japan interns in contributing to OSS in 2017 and 2018
 </details>

-## 2016 --
+## 2016 -- 2019
 {:.year}

 <!-- section -->

--- a/index.md
+++ b/index.md
@@ -37,7 +37,7 @@ Science in IIT Bombay. During the course, I worked for the department as an RA
 in System Administration, and got plenty of opportunity to hone my Linux skills.
 :smile:

-Now, at Yahoo! Japan, I do DevOps for the NoSQL team, principally working on
+Then, at Yahoo! Japan, I did DevOps for the NoSQL team, principally working on
 Cassandra.

 <!-- section -->