Raspberry Pi Experiments and Projects

[paulunderwood]

Originally Posted by jvang

. It seems to get complicated if you were to do something like try to host 2 web servers on your LAN, since each port can only be used by 1 device at a time. Since port 80 is dedicated to HTTP requests or something, you have to work around this somehow.

Having two ssh servers on a LAN is easier as you can specify an external port with the -p switch e.g. ssh <ip_addr> -p 2222. The router will portforward to the specified device (and port).

You can specify that only "joey" uses the server with AllowUsers joey at the end of /etc/ssh/sshd_config (After an edit restart the ssh server.)

Having two http servers is indeed tricky.

[chalsall]

Originally Posted by paulunderwood

Having two http servers is indeed tricky.

Not really... Just use a different port; 8080 is common. Then the URL becomes something like "http://DOMAIN.TLD:8080/".

[science_man_88]

Originally Posted by jvang

I'm having trouble understanding how NAT works. Some analogies I found might be helpful:

Analogy #1: Calling the number of an organization/corporation. If I want to call Bob at his office in a big building, dialing the number of his organization or whatever won't get me in contact with him. I have to include his extension, which helps route me to him. If Bob has asked the receptionist to forward all "Bob calls" to his phone, then I may be able to get in touch with him without his exact extension.

Analogy #2: Sending mail to a building with a bunch of people living/working in it. If I want to send a postcard to Bob at his apartment, I can't just send it to the address of the complex. I have to include his PO Box number to get it directly to him. Although, perhaps Bob has an arrangement with whoever puts mail in the boxes to put all mail with his name on it in his box, even if there is no PO Box number on it.

I have no clue how accurate these analogies are, and if the last part of each one is applicable in any way. I'm especially having trouble with how the returning packets get back to their sender. When a computer on the LAN sends a packet outside of the network, the router replaces the source IP address with its own, so as to avoid conflicts between public and private IPs. So when it receives a response meant for the original computer, how does the router determine those packets' recipient?



How can I tell if it does or doesn't? Personally, I haven't been able to tell if anything has gone wrong since we ran out of IPv4 addresses

The computerphile video about it.

[jvang]

I bought a 128 GB Micro SD card the other day, which I plan to use in the Pi. Making this work seems more complicated than the usual NOOBS installation; I have to format the SD card as FAT32, but the SD card is larger than what Windows wants to format. On the other hand, there is no fancy bootable-partitions sort of thing I have to do to get the Pi to run off of the SD card. Once it's formatted properly, I just download NOOBS directly to it and it should work

[paulunderwood]

Originally Posted by jvang

I bought a 128 GB Micro SD card the other day, which I plan to use in the Pi. Making this work seems more complicated than the usual NOOBS installation; I have to format the SD card as FAT32, but the SD card is larger than what Windows wants to format. On the other hand, there is no fancy bootable-partitions sort of thing I have to do to get the Pi to run off of the SD card. Once it's formatted properly, I just download NOOBS directly to it and it should work

You might consider switching to Rasbian. It has a process to expand an image once installed, although this might work with Noobs too:

http://cagewebdev.com/raspberry-pi-e...f-the-sd-card/

[jvang]

Originally Posted by paulunderwood

You might consider switching to Rasbian. It has a process to expand an image once installed, although this might work with Noobs too:

http://cagewebdev.com/raspberry-pi-e...f-the-sd-card/

I was considering installing an image of an OS, but I figured that I might as well use NOOBS, which is their software for installing a variety of OSes, including Raspbian.

I used mkfs.fat on my Kubuntu system to format the 128 GB SD card, which went smoothly. Then I downloaded the NOOBS netinst zip from their website, and unzipped the folder directly to the root directory of the SD card. It doesn't seem that the netinst version wants to boot, so tonight I'll download the 1.6 GB offline installation to try tomorrow. If that also doesn't work, I'll try a more direct Raspbian image.

[henryzz]

Isn't FAT32 limited to 30GB?

[jasonp]

Fat32 has a limit in the terabytes; Fat16 has a 2GB limit.

ETA: apparently this has changed in recent versions of windows.

[nomead]

The FAT32 limit is indeed 2 TiB (for ordinary 512-byte sectors) but you'll have to format it with something else than the standard Windows GUI tools. There's plenty of third-party tools for that. It can actually be done through the command prompt up to some higher limit, but for example, on Windows 7 the FORMAT.EXE utility says that the maximum number of clusters there is 4177918 which corresponds to about 127.5 GiB. But I've had 2 TB (so about 1.8 TiB) USB hard disks in FAT32, as delivered from the factory. And also 500GB - 1 TB disks with FAT32 running under Windows 98, back in the days. The problem of having a 4 GiB maximum file size still remains, though. And also the file system remains as fragile as before - it is not that resistant to corruption when something goes wrong, for example the power goes out while writing a file, or the system crashes.

The 32 GiB limit was artificially imposed by Microsoft to promote the use of NTFS, and as that proved a bit too complex for embedded systems of the time, they created exFAT. But of course, this being Microsoft, there is an ulterior motive. Parts of the exFAT system are patented, so that device and software makers need to pay license fees to Microsoft in order to use it. And it's not cheap, either. It used to be in the tens to hundreds of thousands of dollars range depending on the product type, but this was about ten years ago, and I have no idea what the costs are nowadays.

[jvang]

Long story short, the Pi didn't like for the whole card to be formatted. We used the Windows diskpart utility to only format 4 gigs of the drive (after wiping it again), and then proceeded as normal. The Pi finally booted up and let me work with NOOBS, just like with the original SD card that was included. After selecting Raspbian from the menu, the Pi set up Raspbian while also formatting the rest of the drive, so I can use the whole 128 gigabytes. Yay!

[paulunderwood]

My 3B+ is doing useful number crunching. I have just ordered a "zero w" to play with. Having only 1 available micro-USB port, it will probably end up as a wireless file/media server with a USB drive attached. Costing £25 for everything except the microSD card --which I have already -- (and peripherals), it is a cheap toy.