/dev/chat

Faheem Mitha

08:54

Since upgrade to stretch, I'm seeing the following email after every reboot. Sometimes multiple times:

> orwell Communications with UPS 1 lost

I assume this is coming from apscupsd. A configuration change, perhaps?

@terdon Hi, it looks like this one was never acted on...

13

A: Why do we have both LVM and an LVM2 tags?

I don't recall seeing a question about LVM1 on this site. It was already obsolete by the time this site started. So for all intents and purposes lvm and lvm2 are currently equivalent. I favor merging them, and making lvm the main tag. (Only moderators can do this.) If an incompatible LVM3 comes...

I think (as @Gilles says) it makes sense to do a merge. Thoughts?

I do think one needs to plan ahead what should be done if lvm3 arrives.

terdon

09:10

@FaheemMitha Done.

Faheem Mitha

@terdon Thank you. What's the plan re lvm3? Assuming it arrives at some point.

terdon

@FaheemMitha No idea. What Gilles suggested there seems reasonable though.

Faheem Mitha

@terdon I'm not exactly sure what he suggested...

terdon

> If an incompatible LVM3 comes along, we can start using lvm3 for it. Then make lvm2 the main tag in the lvm/lvm2 pair and remove the synonym.

Faheem Mitha

Then again, before lvm3 is released, a giant asteroid might hit Earth, and we'll all perish like the dinosaurs.

@terdon Yes, I know. See my comment.

Or, before lvm3 is released, the President of the United States might start World War 3, and we'll all perish like utter idiots.

terdon

09:22

@FaheemMitha I don't really understand what you're missing. Obviously, if lvm3 and 2 are not incompatible, we'll make them synonyms. If they are, we'll make an lvm3 tag.

Faheem Mitha

@terdon Would the questions currently tagged lvm become lvm2 if lvm3 becomes the new version of lvm?

terdon

@FaheemMitha If they're compatible, we would still only have one lvm and both lvm2 and lvm3 would be synonyms of lvm.

If it is significantly different and requires its new tag, lvm3 would be separate and lvm2 and lvm would be synonyms.

Faheem Mitha

@terdon Hmm. Does the current lvm need to be tagged as lvm? And if lvm3 becomes current, it would be the new lvm.

Though maybe not. I don't really know.

terdon

09:38

I don't understand what you mean. I have merged lvm and lvm2 and made the latter a synonym of the former. This means lvm2 no longer exists and if anyone tries to use it, it will automatically be converted to lvm.

So all questions that were tagged with lvm2 are now tagged with lvm instead.

Now, if an LVM3 comes along and doesn't need its own tag, we just keep using lvm. If it does need its own tag, we can create lvm3.

Faheem Mitha

@terdon Yes. I understand. Though in that case, LVM3 questions will not be tagged lvm, correct?

terdon

@FaheemMitha No, not if they're significantly different but why would that be the case?

Let's just cross that bridge if and when we get to it.

Pandya

09:54

@terdon will this question be on-topic on U&L?

terdon

@Pandya Yes, but as they told you there, the answer will almost certainly be no.

Pandya

@terdon Hmm... ok

Faheem Mitha

@terdon Because LVM3 questions are still LVM. To put it another way, if a user hypothetically tags a LVM3 question lvm, would it be removed?

@terdon <Shrug.> Ok.

Ivan Ivanov

Why does Ethernet have 1048 fragments?

Faheem Mitha

@Pandya Broadcom doesn't have free software support, afaik. The usual problem is that the manufacturers don't release the specs.

You could always check with the manufacturers directly. Assuming they reply, that is.

If you get support in India, I'd hang up.

@Pandya If possible, I try to make sure that I purchase hardware that works with free software. It's usually more reliable, and often the hardware itself is better.

Of course, this isn't always possble. E.g. laptops.

terdon

10:14

Also, @Pandya if chili555 from AU couldn't help you, I doubt anyone can. He's very knowledgeable about the wireless driver situation.

Pandya

@FaheemMitha yeah. that's good point.

terdon

He's the only one with the gold wireless badge and the undisputed local expert on wireless.

Pandya

@terdon who's chilli555? I discussed with other user.

answer before question!

@FaheemMitha I'll also purchase FSF certified laptop once.

terdon

@Pandya Heh, yes, I'm just that good :P

2

Pandya

Faheem Mitha

10:23

@Pandya You could, but it's not necessary to go to those lengths, I think. Just research hardware before you buy it. If everyone did that, there would be less Linux hardware questions on SE.

Pandya

Btw, trying to install proprietary driver for long time ^^

@FaheemMitha yes but I may like to go to that length!

Faheem Mitha

@Pandya Ok. :-)

Pandya

Trisquel release based on 16.04 got delayed for 1 year.

Faheem Mitha

11:46

Does anyone know why SE question titles have to be at least 15 chars?

terdon

@FaheemMitha Presumably to avoid stupid titles like "Help!"

And to push you into writing useful, descriptive titles.

Pandya

12:01

what's the command-line alternative to install this driver? because GUI is not responding after long time and I can't see what is happening in background.

Archemar

12:51

Anyone know how populist badge are awarded ? I just got one in SuperUser for a post accepted 15 month ago, and having not receive too much points recently.

Faheem Mitha

13:02

@Pandya What driver?

27

Q: Is the Populist badge broken? Or have I misunderstood?

In this question: First name, middle name, last name. Why not Full Name? my answer has 34 votes and the accepted answer has 10. But no sign of a Populist badge - should I have one? Edit: The accepted answer on that question has received another upvote, so I now have the badge. But either the d...

But whether this is still accurate or not, who knows.

@terdon It's possible to have useful, descriptive titles that are shorter than 15 chars.

And anyone who uses "Help" as a title deserves a sound ducking.

Pandya

Wifi problem solved

1 hour ago, 52 minutes total – 48 messages, 5 users, 0 stars

Bookmarked 22 secs ago by Pandya

Faheem Mitha

@Pandya You could just say that you figured it out...

I must say that AU folks seem helpful. In the average forum they mostly just ignore you. Or you get the occasional sideways hostile glance.

Like a saloon/bar in the Wild West of legend.

terdon

@FaheemMitha Yes, but harder. I assume they added a minimum character limit to force people to use descriptive titles.

Faheem Mitha

@terdon No doubt. Still occasionally aggravating.

My titles tend towards the wordy, so it isn't usually an issue.

But some days I'm in a short, pithy mood.

terdon

Ah, the old short and pithy mood, yes. :P

Faheem Mitha

15:01

I realise this is a vague question, but does LVM know or care what kind of device/structure it's sitting on top of? Or does it just tag it with some metadata and carry on?

Faheem Mitha

15:13

Apparently Solar Airplanes exist.

derobert

16:19

@FaheemMitha what do you mean? It cares that whatever it's on is a block device. Other than that, I think it might do a little to make alignment work.

Faheem Mitha

@derobert I'm not sure exactly what I mean. See the "vague" part.

@derobert I'm having some trouble trying to get this recipe to work.

8

A: How to move / copy logical volume (lv) to another volume group (vg)?

vgmerge lets you merge two VGs. You can also use pvmove to move data within a VG, and vgsplit if you want to go back to multiple VGs.

I want to copy, not move. But pvmove only moves.

I'm examining options. It seems that it might be possible to break a LVM mirror. Do you have any idea? It seems it wasn't possible once, but that might have changed.

Or are there any other alternatives?

Also, any thoughts about unix.stackexchange.com/questions/374291/…

?

I'm currently going with loop devices, but would consider other options.

Short story short - can I use lvconvert to create a mirror and then break it to make a new copy?

I'm looking at voleg.info/lvm2-clone-logical-volume.html

derobert

16:37

@FaheemMitha I think you can somehow...

Faheem Mitha

@derobert So, am I missing anything?

derobert

   lvconvert --splitmirrors Number VG/RaidLV
   · Split images from raid1 RaidLV and use them to create a new LV.
   · Requires --name for the new LV, or the use of --trackchanges.

... from the lvconvert manual

I have no idea why that guide forces the old non-md mirror; manual seems to say that it works with both.

Faheem Mitha

@derobert Yes, I see that. But I need the "other part" of the mirror to be created inside a specific physical extent (or device).

@derobert If you mean the link I posted, it might be out of date, or incorrect.

I had no idea that command existed till I read that page...

No, actually, I don't see what he is forcing.

derobert

@FaheemMitha I'm not sure if there is a way to override the default allocation policy when adding a mirror... trying to find it in the manpage. Of course, you could temporarily change the default policy.

Faheem Mitha

@derobert There's an alloc option.

That man page isn't the chattiest thing around. I wish I could find a better guide.

An up-to-date one, naturally.

  Convert a linear LV to a two-way mirror LV, allocating new extents from specific PV ranges:
   lvconvert --mirrors 1 vg/lvol1 /dev/sda:0-15 /dev/sdb:0-15

This one might be relevant.

But I don't see documentation for the syntax. Sigh.

derobert

16:45

@FaheemMitha looks like you've found it...

Faheem Mitha

@derobert I don't understand how it is supposed to work, though.

What's the syntax?

 /dev/sda:0-15 /dev/sdb:0-15

?

derobert

that's the PV name and the extent numbers, I think. If you look at the next example, you can give just the PV name and let it pick its own extent numbers.

Faheem Mitha

Convert a mirror LV to a linear LV, freeing physical extents from a specific PV:
   lvconvert --type linear vg/lvol1 /dev/sda

This one? ^^

I don't really know what extent numbers are.

Oh. No, that's the other way around.

derobert

They're basically blocks for LVM. LVM stores its metadata in terms of extents. So a logical volume metadata includes a lists of PVs and the extents on each PV

look at the file in /etc/lvm/backup

Faheem Mitha

@derobert Ah, blocks inside the VG?

derobert

16:49

                swap {
                        id = "anPe08-Tj1m-hBYK-Szaw-1oxi-JmGi-jn4qMD"
                        status = ["READ", "WRITE", "VISIBLE"]
                        flags = []
                        segment_count = 1

                        segment1 {
                                start_extent = 0
                                extent_count = 1430     # 5.58594 Gigabytes

                                type = "striped"
                                stripe_count = 1        # linear

that's an example from my machine. The LV "swap" starts at pv0, extent 0 and runs through extent 1430

Faheem Mitha

@derobert Yes, I see.

Are these signposts relative to the containing/enclosing VG?

derobert

No, I think it's relative to the PV

Faheem Mitha

@derobert Oh.

And if the VG contains multiple PVs?

derobert

Then it shouldn't be any different. The LV can contain multiple segments, each one specifies the next set of extents (and each segment can be on a different PV)

Or with striping, striped across multiple PVs.

Faheem Mitha

@derobert Ah, ok.

So, getting back to my question. Do I need to specify a physical device when creating the mirror, or when splitting?

derobert

16:55

@FaheemMitha When creating. Otherwise, LVM will pick for you (and it should pick reasonably—i.e, a different PV than the source)

Faheem Mitha

@derobert ok.

So, something like:

 lvconvert --type mirror --mirrors 1 vg/lvol1 /dev/sda

?

derobert

Yeah, though I'd use --type raid1 as I can't think of a reason to use the old non-md mirror code.

Or as the manpage puts it:

   In  most cases, the mirror type is deprecated and the raid1 type should
   be used.  They are both implementations of mirroring.

Faheem Mitha

Ah, this has a detailed example:

tecmint.com/lvm-storage-migration

@derobert Oh, ok. So

lvconvert --type raid1 --mirrors 1 vg/lvol1 /dev/sda

?

derobert

yep

presuming you want the copy on /dev/sda

Faheem Mitha

Step 9 in that link has:

lvconvert -m 1 /dev/tecmint_vg/tecmint_lv /dev/sda1

derobert

17:00

also, is /dev/sda your PV? And not something like /dev/sda1?

Faheem Mitha

which looks similar.

@derobert Oh, I'm just using whatever the documentation is doing.

I think my current devices are /dev/loop1, /dev/loop2. Test mode - loop devices. Does that look right?

And my actual devices are dev/md1, dev/md2, I think.

Or something like that.

derobert

Does what look right? The lvconvert --type raid1 --mirrors 1 «source-lv» «dest-pv» syntax looks right

pvs or pvdisplay will tell you the PV devices

Faheem Mitha

@derobert ok

root@orwell:/home/faheem# pvs
  PV         VG        Fmt  Attr PSize   PFree
  /dev/loop1 testvg1   lvm2 a--   92.00m  80.00m
  /dev/loop2 testvg1   lvm2 a--   92.00m  80.00m
  /dev/md0   data      lvm2 a--  297.96g 137.96g
  /dev/md1   debian    lvm2 a--  465.76g  16.12g
  /dev/md127 newdebian lvm2 a--  465.40g 324.78g

Those first two entries are my test devices.

derobert

yeah, so for the test you'd use /dev/loop1 or /dev/loop2

Faheem Mitha

@derobert Ok. Trying that now. Have you used any of this in the "wild"?

derobert

17:05

Though I don't think you've created your test LV yet, since both loop1 and loop2 show the same free space.

@FaheemMitha yes

Mainly via pvmove

Faheem Mitha

@derobert I have. I don't know why it isn't showing up. Though they are basically empty.

I created one on each test vg.

@derobert What if you want to do a copy?

derobert

@FaheemMitha I haven't really needed to make copies that often.

Faheem Mitha

@derobert Ok.

derobert

Except as part of moving data, like pvmove does.

Faheem Mitha

Btw, suggestions for a better title?

The current one is awful.

@derobert Copying is conservative.

I mean, if something goes wrong, at least you (might) still have your source volume/filesystem.

When it comes to computers, I'm super-cautious.

Well, computer software.

derobert

17:09

@FaheemMitha Well, mostly when I've been doing that, it's been after replacing disks... and either it's being done by mdraid or alternatively I've built a new machine, then I copy from the old one using tar...

Faheem Mitha

@derobert Yes, I thought I'd let LVM do the copying bit. Because it should be able to, IMO. I could have used dd or something. But I'm not a big fan of those raw write kinds of things.

Too little safety.

derobert

I think your LVM raid1 + split codepath is well-tested, so should be fine. It's pretty similar to how pvmove works, and that's definitely well-tested.

Faheem Mitha

@derobert I'll try it. Thanks for the assistance. And maybe add an answer in a couple of places. This method isn't documented on SE, as far as I can see.

pvmoveis mentioned in a couple of places.

@derobert So, thoughts about test modes? Do you use loop devices or something else?

derobert

@FaheemMitha Loop devices should work. So would a VM. A VM would provide a more isolated test environment.

Faheem Mitha

@derobert True.

Would a chroot work, or do you need something more isolated?

derobert

17:22

Isolated in both protecting the host from f— ups inside the VM, and also in keeping the test from being affected by weirdness on the host.

@FaheemMitha Depends on what you're testing!

Faheem Mitha

@derobert Well, something like the stuff above.

derobert

Those commands are safe enough I'd test them on loop devices.

Being careful, of course, and making sure to use distinct names. A mistaken lvremove will still kill your real volumes

(though lvremove is undoable... as long as you catch it before your next lvcreate/lvextend)

Faheem Mitha

@derobert Good to know. But for something like this I usually use cut and paste from a transcript.

derobert

Yes, a week or so ago I accidentally removed the wrong LV, and got to learn how to undo it. Turns out it's easy with vgcfgrestore

Faheem Mitha

@derobert That must have been scary.

What about removing a volume group?

derobert

17:29

@FaheemMitha Not that bad, from how LVM works it clearly is recoverable, I was quite pleased with how easy it is though.

I was expecting to have to issue a scary lvcreate specifying exactly the same extents...

Faheem Mitha

@derobert What command did you type?

Approximately, anyway.

derobert

@FaheemMitha I'm not sure exactly what vgremove does, but should be recoverable.

@FaheemMitha vgcfgrestore --file /etc/lvm/archive/Zia_00207-4082409.vg Zia ... pretty sure that was the command. Found it in history.

Faheem Mitha

@derobert There's an archive?

derobert

yep

Faheem Mitha

Huh.

derobert

17:32

LVM makes a backup of the metadata each time you change it

Faheem Mitha

@derobert I'll keep that in mind...

Do you know if it ever gets rid of it?

derobert

Yeah. It keeps them for (at least the settings on my system are) at least 10 archives, and any under 30 days in age

... this consumes 324K on my machine

Well, more, actually since they're in /etc and I store /etc in git. But I have no idea to ask git how much space it takes, under any of the reasonably definitions of space used in a deduplicating store.

Search for the "backup" section on your /etc/lvm/lvm.conf

Faheem Mitha

@derobert That seems quite comprehensive.

Since earlier settings usually quickly become irrelevant. Since the data gets overwritten, anyway.

Faheem Mitha

18:55

Does anyone know how to cut and paste with the mouse without introducing lots of extra crap. Some of it tabs, by the look of it.

Kusalananda

Into Vim?

Faheem Mitha

@Kusalananda From Konsole into Emacs. Sorry, I should have been more specific.

Gilles

@FaheemMitha don't select crap?

Faheem Mitha

@Gilles Not helpful.

Gilles

@FaheemMitha if you want a clearer answer, ask a clearer question

Faheem Mitha

19:02

@Gilles I'm cutting and pasting from a Konsole terminal. Very ordinary.

But I seem to be getting extra line endings or something.

derobert

19:45

BTW: I edited unix.stackexchange.com/questions/374282/… earlier today to make it clear—I think I succeeded, but it'd already been through the reopen queue so I don't think it gets another go. Needs two more votes to reopen.

Kusalananda

@derobert One from me now.

derobert

It's open again. Thank you all.

Gilles

@derobert the original version sure didn't make any sense

derobert

@Gilles no, OP was hopelessly confused to start

Gilles

is he the same guy who was trolling (?) insisting to do all kinds of weird stuff by using cat a while back?

derobert

19:56

@Gilles Not sure. Doesn't show on his profile if so, but maybe it was deleted.

Faheem Mitha

20:24

@derobert Well, that approach worked. Do you think it worth adding to the existing answers?

Faheem Mitha

20:36

I've been getting the following by email since upgrade to stretch. I'm not sure to make of it. Should I report it as a bug, or did I somehow cause it? And is it a suitable question for U&L?

ubject: Anacron job 'cron.weekly' on orwell

/etc/cron.weekly/dhelp:
/usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- bdb (LoadError)
        from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from /usr/lib/ruby/vendor_ruby/dhelp.rb:21:in `<top (required)>'
        from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from /usr/lib/ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'

Wifi problem solved

Transcript for