Limiting the capacity of SD cards for the pi

I used to run Xenix on a 15MHz 80286 system, it worked fine.

Yes, probably.

rmdir /mnt/x would work (if it's still empty, which it should be), but that's not necessary.

That's fine. Sockets are what running processes use to talk to each other, they live in the filesystem so they can be found. It makes no sense to "archive" them, so they're ignored by tar.

Yes, these things take time...

It should be /dev/sda for your environment.

/dev/sda is the whole disc. /dev/sda1 is the first partition (a subset of the whole disc), /dev/sda2 the second partition. fdisk is about manipulating partitions, so needs to work on the whole disc. (The partition table is in the first sector/block of the disc)

Indeed the man pages are reference material, on a good system they are complete and correct and occupy a similar position to the datasheet for an IC - essential when you need the precise detail.

They are not and never were intended to be tutorials any more than a complete set of TTL datasheets will tell you which chips to use and how to connect them in order to construct a clock.

It's far more obscure than that :)

The dd name was a joke reference to the IBM JCL command DD (data definition). Originally dd was the universal data format conversion tool capable of converting between ASCII and EBCDIC, adjusting parity, converting case, swapping bytes (endian conversion) and dealing with moving data between block structured devices/files with different block sizes performing block padding as needs be.

It can still do all of this (check the conv section of man dd) should you ever find a need to do *any* of it.

SCO bought Xenix from Microsoft, later the product became SCO Unix after the SysVR4 changes were merged into it.

There's some authorisation caching in sudo, so if you have recently given your password for a sudo command sudo remembers this and doesn't ask again.

Okay thanks Ian.

I've now got passed stage 10 and looking at 11.

Lots of questions now...

Do I need to create a script from your text or can I just copy and paste line by line?

How do I change where to put the new image?

Any suggestions where to put it?

Can I just copy out the image using samba with something I understand. :-)

How do I delete the tarfile and where is it?

Why did we use a tarfile, was it just to reduce the storage size?

Cheers,

Bob.

Sudo sorta remembers you for a time. Very confusing. I dont remember it douing that tears ago..

rmdir /mnt/x

next time use cvzf to get it to tell you what its doing.

I wonder why id did that? patently that is not something worth backing up, but nevertheless...

looks OK

No. partititons are applied to the WHOLE disk which is /dev/sda

so fdisk /dev/sda

Ok just one misstep, but defiinitely three steps forward

You remind me of just how weird and crappy Unix at the command line seemed, back when I first had to do stuff with it

I'd say it was quite an easy drive, but it isn't really suitable for the sorts of crap we used to put on an PDP/11. That drive was spinning all day with half a dozen of us doing stuff on it

Ah. My bad, I was thinking of Venix, not Xenix. Venix was a heap of crap but would run on a 286...just about

Sco Unix was a damned good platform for a small company 'minicomputer'

It even had TCP/IP ... eventually!

We had it running on one of the first 486s. Database for hospitals around the region (St Barts)

You can just copy/paste the lines. When you paste the "echo" one check that the reported number of MB is reasonable, and that the number of sectors being copied is bigger than the last sector shown, before proceeding to the 'dd'

The file name after the "| gzip >" is where the target image will go. It can be any file path, so if you have external filestore mounted with samba it can go there directly. There should be enough space on the live SD card if you remove the tarfile first, the copy it off wherever you need it.

The tarfile is ~/xxx.tar.gz, you can remove it with:

# rm ~/xxx.tar.gz

"~/" is a shortcut for your "home directory". As root, this is /root, so the file is actually /root/xxx.tar.gz. The same applies to the final image: "~/newcard.img.gz" is /root/newcard.img.gz.

The tarfile was used to hold a copy of the OS files while you shrunk the parition. Think of it as zipping up the contents of a disc before replacing it with a new one, then restoring the content from the zipfile.

Final note, I "gzip" (compress) the final image as this saves a lot of space (8GB down to 2.3GB in my case). You'll need to uncompress it before writing it to a new card with Win32DiskImager. 7zip can do this on Windows, if that's how you do it. If you don't want it compressed (and have the space), you can omit the gzip from the last command:

# dd if=/dev/sdc bs=1048576 count=${n_mb} > ~/newcard.img

To pick up on the "dd" thread, that command reads from the input file (if=...), in blocks of 1MB (bs=...) and copies ${n_mb} blocks (count=...). It send the output to "stdout" (nominally the terminal), but we pipe this through gzip to compress it (| gzip", and then direct the output of gzip to the target file (> ~/newcard.img).

Chris,

I was/am trying to evade multi-step solutions. Especially ones that cannot be automated.

Regards, Rudy Wieser

SCO Xenix had MICNET, a LAN based on UUCP over directly connected serial ports. With it running you could cd .. from / and find a directory of machines on the network. It wasn't fast or standard but it worked.

There was a legal business that had it on a 386 running the while firm with about 25 screens on. Cost was a few hours a day to pop tapes in the backup. and a thousand quid support contract with the software authors .

Then a board decision to put a PC on everyone's desk at about £1500 a DESK was made with an annual support contract of about £10,000

Blimey. I missed THAT one. UUCP was something that I spent a large part of my life installing and setting up. It was, for a time, the only way to get "Internet" email in the UK

First question: can you write C (or C++ or Rust, ...) already?

If not, I'd recommend the ANSI edition of "The C Programming Language" by Kernighan and Richie (They are the authors of C).

"The Practise of Programming" by Kernighan and Pike" is also good to have: if you're starting to program because it describes how to write well laid out and documented C code that's easy for other programmers (including yourself in 10 years time) to read, understand and modify. A lot of what it says is directly applicable to other block structured languages such as Java, Algol 60, Algol 68, Pascal and even PL/I. It may even help you to write better programs in other languages such as Perl, Python, Fortran, COBOL and assemblers.

And, if you find that you need tried and tested chunks of code to slot into some project you're developing, its worth knowing about both "Software Tools in Pascal" (Kernighan and Pike) and "Algorithms" (Sedgewick). The latter isn't cheap, but then good books about programming languages and algorithms seldom are. Both these provide runnable example code written in Pascal, which is easy to transcribe directly into C and/or Java (Personal experience) because it was written as a teaching language for use in Computer Science courses.

Thanks again to Ian and TNP and everyone who has helped me get there. I have now managed to get through the process and I have an output file. I need to test that file.

I strongly suspect my settings somewhere but the decompressed file isn't dramatically smaller than the original.

Original = 3,805,184 KB new file = 3,411,968 KB

I targeted getting down from 4GB to 3GB as more than 1GB was empty.

Cheers,

Bob.