I'm a newbie to ActivityPub so please be patient with me.

All intros into ActivityPub speak about how a user of a server A subscribes to a specific community from server B, and then server A will be informed about changes in that community.

But on lemmy it's possible to look at the posts of all communities. For a single concrete community it would be relatively easy: server A gets the request to serve the top post of a community on server B, so A simple asks B for the posts.

But there is also the "posts from all communities" tab on the lemmy front page. This opens questions:

Does each lemmy instance has a full copy of all posts of all communities? If this is true: How are new Instances discovered? Is each Instance distributing all updates to all other Instances?

If each lemmy instance has only a partial dataset (this theory is backed by [1] "Only if a least one user on your instance subscribes to the remote community, will the community send updates to your instance.") then how is the "all posts" view composed? is it in reality not "all" but only "all posts that at least one user of this instance is subscribed to"?

If this is the case: what happens if a bad actor subscribes to all communities of all servers? Is there a maximum number of subscriptions per user?

The source of those questions is, that I'm looking for a way to subscribe to all events of all lemmy instances, to be able to build statistics about upvotes, new posts, comments etc. There seems to be a similar API endpoint for mastadon [2] but nothing for lemmy?!

Dear Linux-Wizards,

I have some USB flash drive that outputs the following errors, when i plug it in:

VGscsi 6:0:0:0: Direct-Access     SMI01    USB DISK01       1100 PQ: 0 ANSI: 6
VGsd 6:0:0:0: [sdc] 491520000 512-byte logical blocks: (252 GB/234 GiB)
VGsd 6:0:0:0: [sdc] Write Protect is off
VGsd 6:0:0:0: [sdc] Mode Sense: 43 00 00 00
VGsd 6:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
VGsd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
VGsd 6:0:0:0: [sdc] tag#0 Sense Key : Not Ready [current] 
VGsd 6:0:0:0: [sdc] tag#0 Add. Sense: Medium not present
VGsd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 00 00 00 00 08 00
VGI/O error, dev sdc, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
VGBuffer I/O error on dev sdc, logical block 0, async page read
VGsd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
VGsd 6:0:0:0: [sdc] tag#0 Sense Key : Not Ready [current] 
VGsd 6:0:0:0: [sdc] tag#0 Add. Sense: Medium not present
VGsd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 00 00 00 00 08 00
VGI/O error, dev sdc, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
VGBuffer I/O error on dev sdc, logical block 0, async page read
VGldm_validate_partition_table(): Disk read failed.
VGsd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
VGsd 6:0:0:0: [sdc] tag#0 Sense Key : Not Ready [current] 
VGsd 6:0:0:0: [sdc] tag#0 Add. Sense: Medium not present
VGsd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 00 00 00 00 00 00 08 00
VGI/O error, dev sdc, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
VGBuffer I/O error on dev sdc, logical block 0, async page read
VG sdc: unable to read partition table
VGsd 6:0:0:0: [sdc] Attached SCSI removable disk
VGsd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
VGsd 6:0:0:0: [sdc] tag#0 Sense Key : Not Ready [current] 
VGsd 6:0:0:0: [sdc] tag#0 Add. Sense: Medium not present
VGsd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 1d 4b ff 80 00 00 08 00
VGI/O error, dev sdc, sector 491519872 op 0x0:(READ) flags 0x80700 phys_seg 1 prio class 2
VGsd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
VGsd 6:0:0:0: [sdc] tag#0 Sense Key : Not Ready [current] 
VGsd 6:0:0:0: [sdc] tag#0 Add. Sense: Medium not present
VGsd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 1d 4b ff 80 00 00 08 00
VGI/O error, dev sdc, sector 491519872 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 2
VGBuffer I/O error on dev sdc, logical block 61439984, async page read

lsblk output looks okayish, disk size is reported correctly.

sdc      8:32   1 234,4G  0 disk

When i first noticed, i hoped maybe only the first Sectors are broken, but now i'm trying with ddrescue and ddrescue -d and see the similar messages:

I/O error, dev sdc, sector 237172352 op 0x0:(READ) flags 0x800 phys_seg 15 prio class 2
sd 6:0:0:0: [sdc] tag#0 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_OK cmd_age=0s
sd 6:0:0:0: [sdc] tag#0 Sense Key : Not Ready [current] 
sd 6:0:0:0: [sdc] tag#0 Add. Sense: Medium not present
sd 6:0:0:0: [sdc] tag#0 CDB: Read(10) 28 00 0e 22 f7 00 00 00 80 00

It's a USB-3 flash drive, so i also tried an USB-2 port hoping that maybe its some connection thing, but it did not help, I see the same error messages.

Normally USB flash drives warm a bit when reading/writing data, this one ist still cold after 25 minutes of ddrecue

Is there anything else i can do?

Backstory is: I was helping someone with their Windows PC and unplugged the stick without ejecting it, then Windows complained and i pressed to "scan and repair drive" which took a while. At 80% a error message appeared similar to: "insert medium into drive" When clicking OK the message reappeared after one or two seconds. It only stopped after unplugging the flash drive.

The user already said something about folders appearing at wrong locations at the drive, so i hope i did not kill the drive but it was already dying. But still feeling bad about this, so i want to try everything and even reach out to you :-)