FTDI chips VCP or VX drivers

The switch (a cheap-ish 10/100 8 port desktop switch) lost it's ability to speak ethernet on the port that the Raspberry-Pi was connected to, the Pi would try DHCP if we connected it to a different switch port. the dead port stayed unresponsive until the switch was power-cycled.

The router (we were using PC for this task) wasn't having any problems. just the switch.

..

The disconnect router was just an example to show it may take some time for the switch / network ARP to get the MACs if there are network changes. I always switch off DHCP, do not see the point of it on a wired LAN with just some devices.

I have 3 rapis online, 1 24/7, and a lot of sensors that use UDP. Bunch of PCs, cable modem, laptop.. 2 cheap 8 port switches full, some POE channels. Never a problem with the network as far as I can remember (been running for years in various configurations). One raspi is web server too, more problems with hackers trying out all sorts of things on the Apache server. Internet is wild wild west ..

You can't open a port that some other process is connected to. In Linux you can open files multiple times from the same process, but not from different processes. Windows enforces that on a per-handle basis rather than per-process.

Cheers

Phil Hobbs

Yeah, there are workarounds, but it's still a serious wart, almost in the same class as the Linux thread scheduler (but don't get me started).

I can't think of a single reason why one would want to be able to do that--AFAIK doing it is _always_ a bug.

Can you?

Cheers

Phil Hobbs

I'm sure that, if "fixed", it breaks something obscure and archaic.

Linux fanbois are great at forgetting their own history. While Microsoft's operating systems are built on a terrible raft of awkward solutions and backwards compatibility... Linux is built on a terrible raft of volunteered solutions and backwards compability.

That any of it at all works is remarkable; that every operating system is a mire of arbitrary decisions, compromises and inconsistent coding, is only natural.

Tim

In Linux you can open files multiple times from any process, unless some mechanism is used to prevent it. For serial ports, the de-facto standard is to create a "lock file" to reserve the port for your use. This was first done in UUCP and the lockfile mechanism still refers to that.

There have been attempts at creating variants of the serial ports device files that only allow exclusive opens (cua) but they have been abandoned.

In some cases I open a serial port in once process to do the serial I/O in 3-wire fashion and in another process to use the control lines for random input or output and it still works fine in the current versions. If course one process only does read/write and the other only does ioctl to read or set the control lines.

(no idea if the systemd folks already have plans to deprecate that)

I have always considered it a big bug / misfeature in Windows that a backup program cannot open files that are open in another process and thus has to skip them in the backup. Open files tend to be valuable, and valuable files tend to be open. And then THOSE are the files that are skipped in the backup! Disaster...

Of course later a mechanism was introduced to solve this (volume snapshots) but it requires dedicated backup software. You still cannot zip or rar a directory tree where some files are open. Stupid.

Yikes! Backing up an open file is an invitation to a corrupted backup. There's no guarantee that the file is in a consistent state when a program is using it, and you wouldn't find that out till you tried to restore it.

Cheers

Phil Hobbs

I obviously mis-remembered, thanks. Haven't written communications software in about a decade.

Cheers

Phil Hobbs

That said, there are plenty of applications that should open a file in read-only mode, so other things can still read it. Or open it once to load it into memory, then open it again to save changes. Some PDF readers do this, for example. Handy when I'm iterating changes.

Tim

Neon John wrte:

Limited view of reality. Any wireless network can be jammed by even the simplest technology. Permanently destroyed by EMP. Infiltrated. Take a moment and type in google: WPA2 hacked

Old hat.

For toy applications it may or may not do. :-) I would not send any sensitive data over it.

So you prefer "having no backup at all" over "having a backup that might be inconsistent"?

You betcha. The backup s/w can complain and ask you to close the files.

Cheers

Phil Hobbs

Neon John

So sad, you did not learn a thing. Waste of time.

I beg to differ. Microsloth VSS (Volume Shadow Copy Service) allows backing up and restoring files while the files are being written to or read by other applications: I've been using various Windoze image backup programs for many years and can testify that VSS mostly works. Unfortunately, about 10 years ago, I decided to use an image backup program that used VSS, but wasn't really tested very well by either the programmers or the users (me). It went badly, very badly. Today, I beat the hell out of anything I use for backup and things go much better.

Also see VSSadmin:

Macrium Reflect: Very easy to use and so far quite reliable. However, it's a total horror to install and setup. Program updates are very easy. Free for personal use. It's blindingly fast and I have no problem running an image backup while I'm reading email or posting drivel to Usenet.

RSTS on the PDP11 was great. It timeshared a dozen people and ran solid between power failures. It had a tiny kernal, then multiple runtime systems (really OS's) and then various user environments.

That could potentially help if the inconsistencies were purely OS things li ke disk cache or file system buffers, but there's no guarantee whatsoever t hat J Random App maintains consistency even at that level.

I keep work files in git repositories and do volume backups with a live CD.

Cheers

Phil Hobbs

"Looking at Common VSS Myths" I'm not a big fan of Microsloth, but I think they got VSS right (after a few bad starts). However, if VSS fails to create a shadow copy for some reason, it will belch a nasty error message on the screen so that the problem can be corrected. Having an anti-virus program scan the entire hard disk during an image backup is a good way to produce such an error.

I've run verify passes on my image backups and find that only the usual mess of Windoze logging, snooping, and "telemetry" files are the only ones that show a discrepancy. I once found a large database that failed the verify pass. Upon inspection of the transaction files, I found that the index pointers and data were consistent with what the database had been just prior to running the backup. Good enough as I didn't expect to backup all the data to the last millisecond.

My big problem is that I cannot get customers to do backups unless the backup program backups everything, is painless, not disruptive, fast, and reliable. That means no incremental backups or file by file backups. It's taken me many years to get to this point and I'm not about to throw away these features because there MIGHT be some mangled data. I would rather recover what little is lost by hand, than not have any backup at all because the customer was too busy or lazy to run the backup.

However, the authors of Macrium Reflect thought about the problem and have 2 answers. One is to create a book CD or flash drive running Windoze PE. Boot this custom CD and there are no open files on the hard disk drive. The other is to add Macrium Reflect to the hard disk boot menu. On boot, the machine displays for 10 seconds a choice of boot partitions, Windoze and Macrium. If the user does nothing, it boots into Windoze. However, if they select Macrium, it brings up a stand alone version of the backup/restore program. These two methods are also handy for machines that fail to boot for one reason or other.

The Linux LiveCD is similar to the Windoze PE boot environment. Same idea where there are no open files during the backup. I did it like that using Acronis True Image for many years. It worked fine, but my customers would not use it. They didn't want to boot from the CD and did not want to go through an arcane question and answer process in order to get a decent image backup. I had the same problem with Clonezilla. With Macrium, there's an icon on the desktop that says "backup everything". They plug in a USB 3.0 hard disk drive, punch the backup button, make sure it starts, and walk away. It's not as fast as running it from a bootable CD or flash drive, but good enough.

Drivel: Some "experts" believe that VSSadmin should be renamed because it is used by many virus and ransomeware programs to burn the bridges behind them. I'm undecided if it's a good, bad, dumb, evil, dangerous, or stupid idea.

For a single process, yes that should be a bug. For another process it's very handy (and dangerous:), I use this feature all the time when programming embedded stuff, can have a terminal open to some serial gizmo then use another script to write stuff to /dev/ttyUSB0 with the right char/line delay, and the "progress dots" show up on the open terminal. Got a sendUSB script on a right-click, doesn't even care about baud etc, just assumes the port is already open. It works because Linux treats almost everything as a file and unless locked anyone else can read and write to it. No idea how to do something like that in Windows, there end up having to write custom terminal apps with the download stuff built in.

Terry