shamelessly stolen from nixCraft on mastodon
Your USB is probably named '/' or '~' so give that a go.
this post was submitted on 05 Dec 2023
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When you hit enter on the DD command, and your main storage light suddenly starts flashing.
When you hit enter on the DD command, and your eyes suddenly start flashing.
Little Jimmy wanted to try Fedora, But little Jimmy is no more. For what he thought was his external drive, was actually his cerebral core
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That was great :D though I'm afraid that this is kind of me, considering I have a file server on my vacuum robot
So? I'm just creating an 8 GiB swap file.
Try btrfs, where with only 5 hours of research you can create a swap file without writing the entire file.
Also there is no other option, the 5h are non-optional.
After doing that twice, In my / now lives
/swapfile-howto
# this is btrfs not a normal file system.
# We have to create and allocate the file in a btrfs friendly way,
# and tell btrfs to not move or segment it.
touch /swapfile999
chmod 600 /swapfile999
truncate -s 0 /swapfile999
chattr +C /swapfile999
fallocate -l 999G /swapfile999
mkswap /swapfile999
swapon /swapfile999 -p 200
I admire your dedication, but you really could've just done this
btrfs fi mkswapfile --size 16G /swap
swapon /swap
Huh, thank you for telling me, I'll amend the file with that info. This being a thing will probably spare many the troubles I experienced.
I did some digging to reconstruct what happened in my case. The file was created on 2022-12-08, and I remember this being after I rediscovered my earlier approach, from - going by my browsing history - mid september 2022. I worked through plenty of wiki pages at the time, including the btrfs docs on swapfiles, where I probably got my commands. The truncate in there to fix earlier mistakes is something I would keep in, but not add myself, so I must have copied that pages solution. Interestingly, going by archive.org, between dec 02 and dec 13 the documentation on btrfs fi mkswapfile was added to that page.
I am in no way confident in my memory here, but I vaguely recall seeing that command, and being somewhat surprised to not remember it from earlier. That confusion may have even contributed to pushing me to create the file.
Had I seen it, I probably would have tried the command and seen it not exist. Following the note of btrfs 6.1 being required, I would have checked the version and seen that my distro didn't have btrfs-progs 6.1, not even as an alpha on the development channel.
I may also have remembered there being multiple commands needed earlier, and not wanting to deviate from the proven method dismissed the apparently simpler method.
To complete this very meaningful and productive story, on 2022-12-23 my distro got the early christmas present of btrfs-progs 6.1 as an unstable release in the dev channel. After many retractions and republishings of a total of 4 subversions, on 2023-03-04 the first stable release of 6.1.x was made available.
I was 6 months early. Or rather the btrfs devs were 6 months late.
Edit (actually not edit because I didn't send yet):
I actually checked the repo and the documentation changed on dec 06. Here is the commit. The corresponding release occurred on dec 22.
Dumping 30mins into writing this actually resulted with a memorable story. By chance I stumbled over the documentation of a new feature, 2 days after it had been written, but 2 weeks before even the first alpha release containing it was created.
Obligatory useless use of dd comment.
That was an interesting read, thank you!
I haven't touched dd since I read that about a year ago, super interesting!
For people that use dd because they like the progress bar, I highly recommend pv.
Except the proposed alternative should not be cp or pv, but dd bs=4M oflag=direct,sync status=progress.
I feel like I'm taking crazy pills with all the advice in this thread, because for USB keys you will otherwise end up instantly filling the write cache... which will block the apparent progress of the copy operation (so why even use pv since all you're doing is measuring your RAM speed and available cache size) as well as heavily slow down (even potentially partially freeze in some circumstances) the rest of your system as the kernel is running out of free pages and can't flush caches fast enough due to the slow-ass write speeds of usb keys.
* (Alternatively there is a kernel setting somewhere to disable caching globally for a block device... but in most cases caching is good, just not when you're flashing an ISO).
so why even use pv since all you're doing is measuring your RAM speed and available cache size
This is probably why pv progress fills in a second but is only done after a few minutes. Nonetheless, shell redirect, cat, cp work fine and handle blocksize and cache dynamically.
Your worst case scenario never happened to me after years of using pv/cp for flashing sticks/overwriting/copying partitions, even with some ...risky mount settings. Honestly doesn't make much sense to me either. Again, dd isn't some sort of magical safe handle to make the process progress smoothly. Like i use to say, dd is a skalpell, not a shovel.
I mean yeah, the bits end up where they should. It's just that the speed/progress indication is near useless with pv since at the end of the copy you still need to wait for the entire write buffer to be flushed (2 GiB in my experience, which can take several minutes).
So IMO dd with at least oflag=osync,odirect is safer than cp and pv with which a newbie might forget to run sync and unplug the usb key immediately, so they'll be missing a lot of data.
Maybe some people use dd for the wrong reason, it's their problem, but the solution is to use dd bs=4M oflag=osync,odirect, not to use cp.
It was less useless for that purpose when cp and cat were less I/O efficient compared to dd with the appropriate block size, which isn't as much the case now as it used to be.
Another advantage of having a NVMe SSD, hard to confuse /dev/nvme0n1p2 with /dev/sda1
It's even easier to prevent confusion if you use /dev/disk/by-id/ id's, it only took a few times of overwriting the wrong disk to figure that out.
I think that does the opposite for me lol
When I accidentally decimated my external hard drive, it had NTFS cause there were a few windows machines I would plug it in. Then I reformatted the disk but then I thought to myself, should I have another partition for my Linux machine because that drive gets corrupted and then I need to plug to a Windows machine to repair it once in a while. Then I created an ext4 partition on the disk. Then a few days after I shrinked the NTFS partition and extended the ext4 to the whole disk. Now that disk only has one partition called sda2. Which is kinda weird but makes it easier to distinguish from others disks on the system.
How can I figure out which direct device is associated with a specific id?
Not sure if it is equal on all distros but on every one I have used it's a readable string of muliple components. One of them is "usb" for a usb mass storage, so if it is the only one you have connected to your computer it is very obvious. For like sata disks it has the manufacturer and serial on it so you can match what drive it is you want to write to. Also, the name is pretty unique (on your sysytem at least, globally I don't know), so even if you swap hardware around, you cannot write to the wrong storage if you got the right name. Like "sdb" can be reassigned, but the id is an id.
ˋblkidˋ or take a look around /dev, devices are symlinked to their various attributes.
Even if it's similar names I'd normally plug in USB, do dmesg, then issue a command with latest device name.
I just make use of my paranoia, so I triple and quadruple check. Then get a coffee and quadruple check again. Never messed up once
Fun fact: you can use cat image.iso > /dev/device and it (should) just works.
Or pv if you want a progress bar.
Assuming /dev/device is not a symbolic link, you might as well
cp image.iso /dev/deviceSure, if you're a little bitch.
Yay, more ways to (accidentally) destroy my data!
That's why it called dd: don't dare
I always use the status=progress argument.
That ain't why that light isn't blinking.
Because this USB stick doesn't have light
Anyone who hits enter on a dd command without triple-checking it gets exactly what they deserve.
Goofoyou, goofoyou!