I've been using this extensively recently. I was setting up virtual machines that boot a live ISO containing all the software for the machine. I build that ISO with nix. Sometimes I need to change a small config file, which would lead to generating a new 1.7GiB ISO, but 99.9% of that ISO is identical to the previous one. So I used rsync. Blew my mind when after a day of working on these images, uploading 1.7GiB ISO after 1.7GiB ISO, wireguard showed that I had only sent 600MiBs.
Fun surprise, rsync uses file size and modified time first to see if the files are identical. Nix sets the time to Jan 1st 1970 for reproducible builds, and I suspect the ISOs are padded out to the next sector. So rsync was not noticing the new ISO images when I made small changes to config files until I added the --checksum flag.
This small document shows what computer science looked like to me when I was just getting started: a way to make computers more efficient and smarter, to solve real problems. I wish more people who claim to be "computer scientists" or "engineers" would actually work on real problems like this (efficient file sync) instead of having to spend time learning how to use the new React API or patching the f-up NextJS CVE that's affecting a multitude of services.
6 characters or fewer passwords, if there were passwords at all. Phreaking still worked into the 90s, and all sorts of really stupid things were done without really thinking about the security at all. They'd print out receipts with the entire credit or debit card number and information on it, or carbon copy the card with an impression, and you'd see these receipts blowing around parking lots, or find entire bags or dumpsters full of them. Knowing an IP address might be sufficient information to gain access to systems that should have been secured. It's pretty amazing that things functioned as well as they did, that society was as trusting and trustworthy as it was, that we were able to build as much as we did with as relatively a tiny level of exploitation that happened.
If the same level of vulnerability was as prevalent today as it was back then, civilization might collapse overnight.
I've been using this extensively recently. I was setting up virtual machines that boot a live ISO containing all the software for the machine. I build that ISO with nix. Sometimes I need to change a small config file, which would lead to generating a new 1.7GiB ISO, but 99.9% of that ISO is identical to the previous one. So I used rsync. Blew my mind when after a day of working on these images, uploading 1.7GiB ISO after 1.7GiB ISO, wireguard showed that I had only sent 600MiBs.
Fun surprise, rsync uses file size and modified time first to see if the files are identical. Nix sets the time to Jan 1st 1970 for reproducible builds, and I suspect the ISOs are padded out to the next sector. So rsync was not noticing the new ISO images when I made small changes to config files until I added the --checksum flag.
Well-written, succinct.
This small document shows what computer science looked like to me when I was just getting started: a way to make computers more efficient and smarter, to solve real problems. I wish more people who claim to be "computer scientists" or "engineers" would actually work on real problems like this (efficient file sync) instead of having to spend time learning how to use the new React API or patching the f-up NextJS CVE that's affecting a multitude of services.
to be fair level of security of systems back then was pretty fucking bad
6 characters or fewer passwords, if there were passwords at all. Phreaking still worked into the 90s, and all sorts of really stupid things were done without really thinking about the security at all. They'd print out receipts with the entire credit or debit card number and information on it, or carbon copy the card with an impression, and you'd see these receipts blowing around parking lots, or find entire bags or dumpsters full of them. Knowing an IP address might be sufficient information to gain access to systems that should have been secured. It's pretty amazing that things functioned as well as they did, that society was as trusting and trustworthy as it was, that we were able to build as much as we did with as relatively a tiny level of exploitation that happened.
If the same level of vulnerability was as prevalent today as it was back then, civilization might collapse overnight.