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Messages - Mad Penguin

These guys look interesting, although not physically in the UK is looks like they sell into the UK;
If anyone's tried one of these I'd love to hear ...
Linux Support / Re: What is possible?
July 28, 2022, 04:34:34 PM
Once you connect, as soon as you try to access something that's not public, it should either ask for credentials or look for saved credentials .. but then it will only be able to see files within the security scope of the credentials you provide. i.e. it should do what a Windows box does ...
Linux Support / Re: What is possible?
July 28, 2022, 04:19:04 PM
Hi, I think the answer is "pretty close", depending on your distro. Some file managers are better than others with regards to "samba" integration, but historically "I" would consider "samba" to be better as Windows file sharing that a Windows machine, albeit configuring enterprise level permissions gets more interesting.

I currently use KUbuntu so have the "Dolphin" file manager. If I click on "Network" I'm offered "Bluetooth", "Google Drive", "MTP Devices" and "Shared Folders (SMB)". Double click on the last one and it scans the network for local Windows file servers. Once you've navigated to a server/folder you want, you can right click and "Add to Places" and it becomes a permanent shortcut on your folder list. So next visit (after reboot for example), double click on the shortcut should take you there ...
Hi, well, technically I can see hot the "non-free" bit might sound a little worrying. However (!) non-free in this context doesn't mean necessarily "paid for", but rather that it comes with "strings attached". These strings would typically be detailed in the terms and conditions provided and might be something like; you agree not to try to reverse engineer the code, modify it, put your name on it and sell it etc etc ..".

So the answer literally would be; "it depends on the terms and conditions / license that comes with the firmware in question", but typically, I would not expect Debian to include any software that would be illegal to install. So "non-free" in this context typically means "you're not free to do whatever you want with it", rather than "you need to pay for it".

(Caveat; some software I guess may be subject to export licenses and sanctions etc, so if you're installing in certain countries then I guess there may be an issue .. but for the countries I have in mind, it still may not be an issue ... ;-)  )

... there is always a trade-off between being able to read and track the terms and conditions for every bit of software you use (which IMHO would be quite an ask) , and trusting your supplier not to lure you into installing something you shouldn't.

Edit: it would seem there is a technical definition of what goes into "non-free", which is software whose license does not comply with Debian's definition of "free software". (https://www.debian.org/social_contract#guidelines)
Mmm, well unless you can get someone in who knows corosync/Linux, all I can recommend is;
  • Read the corosync docs, it's all online / open source
  • Aim to resolve "why" the servers aren't sync'd
  • After resolving, the "promote" option from the corosync shell should let you choose which master you prefer
If the cluster is set up correctly, my expectation would be that rebooting the current secondary should attempt to resolve the issue and reconnect the cluster, but depending on "why" it failed and how it was set up, it's not a 'given'. You may still need to do a little work to resolve the issue. At the end of the day the fallback process for this kind of thing would be to remove the secondary, clean it's local config files, then re-add it to the cluster. If this is a production environment, I wouldn't attempt this unless you know what you're doing.
Typically I'd duplicate the setup in VM's, break it, then attempt to resolve it ... before trying it on the live servers.
Quote[font="Open Sans", sans-serif]Corosync .. I'm not very familiar, but as I understand it, Corosync is essentially a very lightweight generic application level clustering tool for synchronising configuration files across a series of 'clustered' servers.[/font]
Corosync runs on Linux, but it may also run on other *nix systems, not sure .. but it appears to be developed by a community that's not specifically linked to SAP .. but it may be that SAP provide it as a component of their product as it's effectively an application in it's own right rather than being a "part" of Linux as such. I guess it maybe comes down to who/what installed or maintains it. Did you install and configure it manually, or did it get installed as a part of the SAP installation?
Ok, so it doesn't look like your two nodes are in-sync, in which case I wouldn't expect to be able to switch the master node. First thing you need to do is get them in sync again. If you run a status command on "both" nodes, see what each node thinks the status is. It may be that both nodes think they are primary for example, i.e. split brain syndrome. I would be expecting to see 'something' against 'exitreason' from at least one of the servers which should help.
It's always difficult with two servers, once the link is severed, getting quorum again means telling one of the servers it's not master even tho' it might think it is. Having a third server makes arbitration much much easier for most of the time. (I know quite a few people who run a third "dummy" server just to get a quorum of >1 so if one server goes down you're left with a node count of two, which means the remaining server know's it has quorum and should still be master.

Corosync .. I'm not very familiar, but as I understand it, Corosync is essentially a very lightweight generic application level clustering tool for synchronising configuration files across a series of 'clustered' servers. I have used it in the past, can't say I was terribly impressed.

Incidentally I notice one of the servers lists "stonith" capabilities, which is designed to prevent split-brain. Historically STONITH (Shoot The Other Server In The Head) required special hardware, so essentially if a server spots a problem with the other, it literally kills it and takes over .. so did server #1 go down when server #2 got promoted to master?

I think the status commands are "crm status" and "pcs status", but it's a long time since I used it. Again, this is a non-trivial issue, if you're a Windows Admin you might want to find a local Linux guy you could hand it off it.

Hi Elf40, 

So I'm not completely clear on your setup here .. you have two servers, or two virtual servers, or two servers and two virtual servers?  And when you say cluster, are you talking about a specific type if Linux clustering, or some SAP Application specific clustering?

If this is Linux clustering with a highly available SAP database, you will need to do a little linking to make the two stay in sync and the linking would depend on your flavour of clustering. If this is all SAP / SAP clustering, then this sounds like an issue for SAP or at least a SAP engineer.

At the end of the day, if you're running commercial / enterprise Linux, a commercial application, and running on a Microsoft cloud service, ultimately you might want to consider a commercial support contract :)
Linux Support / Re: New install setup
July 27, 2022, 03:57:22 PM
Ok, so if you're not familiar with "vim", you might want to try "nano", which is reminiscent of the old editor from wayback when (CP/M?) which gives some on-screen help. VIM operates in two modes, edit and command. By default you can edit and just type in the lines you want ... to quit you need to enter command mode, which is a colon (":"), then "w" is for write and "q" is for quit.

$ cat - > packages
$ cat packages

Where ^C means hold down control and press "C"
(copy-at-terminal "-" means take input from keyboard, ">packages" means output to a file called packages)
Linux Support / Re: New install setup
July 27, 2022, 03:05:04 PM
Heh, probably more ways to do that than I care to imagine :) .. easiest mechanism that springs to mind;
vi packages
# enter names of packages, hit return after each one
# :wq to quit editor
apt install `cat packages`

So "cat packages" is "copy-at-terminal", or just output the contents. The "ticks" around `cat packages` are actually "backticks", which mean evaluate the contained command .. so apt install followed by an evaluation of "cat packages" would equate to "apt install package1 package2 ..." or whatever names you entered into "packages" .. if that makes sense?  
(a long and distant memory is telling me that "cat" is the Linux equivalent of the DOS "type" command, but I could be wrong)

Linux Support / Re: New install setup
July 27, 2022, 02:29:34 PM
Hey Dude, I'm not sure it's something that would be worthwhile for "me", but if it's something you want to do there are certainly Linux tools for it. Consider however;
  • Software installation is via a package manager, say "apt" on Ubuntu .. so installing your custom list of software is as simple as "apt install [... list of package names]".
  • User customisation is typically via configuration files held in the user's filesystem, typically beginning with a "."
So, if you maintain a copy of your home folder and a list of the names of the packages you have installed, installing a new system could be as easy as restoring your home folder and "apt install ..." .. assuming I've understood what it is you're looking for?

Linux Support / Re: USB Boot
July 26, 2022, 09:43:23 PM
Hi Muhuf,

As Keith said, at first glance I just thought you'd spelt Linux incorrectly .. :-) .. Assuming you mean the Linx8 tablet, I suspect you should be able to pair it with a bluetooth keyboard, or alternatively a standard USB keyboard if you can find a USB-C -> USB adapter / cable.

Be interested in your aims here, looks like it only comes with 1G ram, so I doubt it's going to run anything useful in terms of a desktop .. I suppose you might get XFCE up but I'd be relatively confident it's not going to run Firefox or Chrome, certainly not in any meaningful way ??

(If you're looking for an ultra-cheap touchscreen Linux device with a usable amount of memory, you might be better off with a Raspberry Pi4 (which goes up to 8GB) and the official RP touchscreen (which I think is 12 quid))

Mm, so now I'm intrigued. Most Linux distro's come with virtualisation "out of the box", Ubuntu for example comes with KVM/Libvirt/libvirtmanager which allows you to manage lots of VM's distributed over multiple servers. Proxmox for a more enterprisey solution .. what do you get from VMWare for Linux that doesn't come with the free options? Kinda feels like there must be something significant for people to pay and be subject to a relatively restrictive license, but it's not something I'm aware of?

I used VMWare server for Linux many (15?) years ago, just because I had some .vmdk machine images to load up, but I sort of thought since then it had died off .. mostly an assumption, but I couldn't really see the point of paying for something what was "built-in" and free?

Mmm, not entirely sure why you'd want to run virtualisation on Windows when the vast majority of the World runs it on Linux, but hey, it should also work. Not aware that VMware will do anything KVM or ProxMox don't, other than take money off you for Windows and VMware licenses (!)
Ok, so imaging a DS in itself can be problematic, especially if you want to do a restore and don't have hands on. If you want actual images, what about virtualising your DS and running your mailserver in it's own VM. If you were to do this with KVM for example you would get easy access to the raw images for backup (and restore) and also snapshot facilities. (example screenshots attached) Unless your mail-server is unusually performance sensitive, typically you're not going to see any difference relative to running it native. You can automate both snapshots and image backups from the command line (or CRON) using "virsh" (and it does have specific support for 'hot' image backups)
I'm saying KVM, but if you have direct access to the machine, ProxMox (https://www.proxmox.com/en/) provides a pretty comprehensive bare-metal solution which adds all sorts of bells and whistles above and beyond standard KVM, not used it in a few years but I'd be fairly confident is will have a number of 'hot' backup options.