free space is missing after dist upgrade on lzo compressed vol

free space is missing after dist upgrade on lzo compressed vol

[Brenton Chapin]

I was running Lubuntu 14.04 on btrfs with lzo compresssion on, with
the following partition scheme:

sda5   232M  /boot
sda6   16G   /
sda7   104G /home

(sda5 is ext4)

I did 2 distribution upgrades, one after the other, to 15.04, then
15.10, since the upgrade utility would not go directly to the latest
version.  This process did a whole lot of reading and writing to the
root volume of course.  Everything seems to be working, except most of
the free space I had on sda6 is gone.  Was using about 4G, now df
reports that the usage is 12G.  At first, I thought Lubuntu had not
removed old files, but I can't find anything old left behind.  I began
to suspect btrfs, and checking, find that du shows only 4G used on
sda6.  Where'd the other 8G go?

"btrfs fi df /" reports the following:

Data, single: total=11.01GiB, used=10.58GiB
System, DUP: total=8.00MiB, used=16.00KiB
System, single: total=4.00MiB, used=0.00B
Metadata, DUP: total=1.00GiB, used=397.80MiB
Metadata, single: total=8.00MiB, used=0.00B
GlobalReserve, single: total=144.00MiB, used=0.00B

"btrfs filesystem show /" gives:

Label: none  uuid: 4ea4ac08-ff37-4b51-b1a3-d8b21fd43ddd
    Total devices 1 FS bytes used 10.97GiB
    devid    1 size 15.02GiB used 13.04GiB path /dev/sda6

btrfs-progs v4.0

"du --max-depth=1 -h -x" on / shows:

29M    ./etc
0    ./media
16M    ./bin
354M    ./lib
4.0K    ./lib64
0    ./mnt
160K    ./root
12M    ./sbin
0    ./srv
4.0K    ./tmp
3.1G    ./usr
442M    ./var
0    ./cdrom
3.8M    ./lib32
3.9G    .

And of course df:

/dev/sda6        16G   12G  2.5G  83% /
/dev/sda5       232M   53M  163M  25% /boot
/dev/sda7       104G   46G   57G  45% /home

And mount:

mount |grep sda
/dev/sda6 on / type btrfs
(rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@)
/dev/sda5 on /boot type ext4 (rw,relatime,data=ordered)
/dev/sda7 on /home type btrfs
(rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@home)

uname -a
Linux ichor 4.2.0-18-generic #22-Ubuntu SMP Fri Nov 6 18:25:50 UTC
2015 x86_64 x86_64 x86_64 GNU/Linux

I can live with the situation, but recovering that space would be nice.
-- 
http://brentonchapin.no-ip.biz

Re: free space is missing after dist upgrade on lzo compressed vol

[Hugo Mills]

[-- Attachment #1: Type: text/plain, Size: 2849 bytes --]

On Fri, Nov 13, 2015 at 04:33:23PM -0600, Brenton Chapin wrote:
> I was running Lubuntu 14.04 on btrfs with lzo compresssion on, with
> the following partition scheme:
> 
> sda5   232M  /boot
> sda6   16G   /
> sda7   104G /home
> 
> (sda5 is ext4)
> 
> I did 2 distribution upgrades, one after the other, to 15.04, then
> 15.10, since the upgrade utility would not go directly to the latest
> version.  This process did a whole lot of reading and writing to the
> root volume of course.  Everything seems to be working, except most of
> the free space I had on sda6 is gone.  Was using about 4G, now df
> reports that the usage is 12G.  At first, I thought Lubuntu had not
> removed old files, but I can't find anything old left behind.  I began
> to suspect btrfs, and checking, find that du shows only 4G used on
> sda6.  Where'd the other 8G go?

   Do you have snapshots? Are you running snapper, for example?

   The other place that large amounts of space can go over an upgrade
is in orphans -- files that are deleted, but still held open by
processes, and which therefore can't be reclaimed until the process is
restarted. I've been bitten by that one before.

   Hugo.

> "btrfs fi df /" reports the following:
> 
> Data, single: total=11.01GiB, used=10.58GiB
> System, DUP: total=8.00MiB, used=16.00KiB
> System, single: total=4.00MiB, used=0.00B
> Metadata, DUP: total=1.00GiB, used=397.80MiB
> Metadata, single: total=8.00MiB, used=0.00B
> GlobalReserve, single: total=144.00MiB, used=0.00B
> 
> "btrfs filesystem show /" gives:
> 
> Label: none  uuid: 4ea4ac08-ff37-4b51-b1a3-d8b21fd43ddd
>     Total devices 1 FS bytes used 10.97GiB
>     devid    1 size 15.02GiB used 13.04GiB path /dev/sda6
> 
> btrfs-progs v4.0
> 
> "du --max-depth=1 -h -x" on / shows:
> 
> 29M    ./etc
> 0    ./media
> 16M    ./bin
> 354M    ./lib
> 4.0K    ./lib64
> 0    ./mnt
> 160K    ./root
> 12M    ./sbin
> 0    ./srv
> 4.0K    ./tmp
> 3.1G    ./usr
> 442M    ./var
> 0    ./cdrom
> 3.8M    ./lib32
> 3.9G    .
> 
> And of course df:
> 
> /dev/sda6        16G   12G  2.5G  83% /
> /dev/sda5       232M   53M  163M  25% /boot
> /dev/sda7       104G   46G   57G  45% /home
> 
> And mount:
> 
> mount |grep sda
> /dev/sda6 on / type btrfs
> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@)
> /dev/sda5 on /boot type ext4 (rw,relatime,data=ordered)
> /dev/sda7 on /home type btrfs
> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@home)
> 
> uname -a
> Linux ichor 4.2.0-18-generic #22-Ubuntu SMP Fri Nov 6 18:25:50 UTC
> 2015 x86_64 x86_64 x86_64 GNU/Linux
> 
> I can live with the situation, but recovering that space would be nice.

-- 
Hugo Mills             | Happiness is mandatory. Are you happy?
hugo@... carfax.org.uk |
http://carfax.org.uk/  |
PGP: E2AB1DE4          |                                              Paranoia

[-- Attachment #2: Digital signature --]
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Re: free space is missing after dist upgrade on lzo compressed vol

[Brenton Chapin]

Thanks for the ideas.  Sadly, no snapshots, unless btrfs does that by
default.  Never heard of snapper before.

Don't see how open files could be a problem, since the computer has
been rebooted several times.

I wonder... could the distribution upgrade have moved all the old
files into a hidden trash directory, rather than deleting them?  But
du picks up hidden directories, I believe.  Doesn't seem like that
could be it either.

On Fri, Nov 13, 2015 at 4:38 PM, Hugo Mills <hugo@carfax.org.uk> wrote:
> On Fri, Nov 13, 2015 at 04:33:23PM -0600, Brenton Chapin wrote:
>> I was running Lubuntu 14.04 on btrfs with lzo compresssion on, with
>> the following partition scheme:
>>
>> sda5   232M  /boot
>> sda6   16G   /
>> sda7   104G /home
>>
>> (sda5 is ext4)
>>
>> I did 2 distribution upgrades, one after the other, to 15.04, then
>> 15.10, since the upgrade utility would not go directly to the latest
>> version.  This process did a whole lot of reading and writing to the
>> root volume of course.  Everything seems to be working, except most of
>> the free space I had on sda6 is gone.  Was using about 4G, now df
>> reports that the usage is 12G.  At first, I thought Lubuntu had not
>> removed old files, but I can't find anything old left behind.  I began
>> to suspect btrfs, and checking, find that du shows only 4G used on
>> sda6.  Where'd the other 8G go?
>
>    Do you have snapshots? Are you running snapper, for example?
>
>    The other place that large amounts of space can go over an upgrade
> is in orphans -- files that are deleted, but still held open by
> processes, and which therefore can't be reclaimed until the process is
> restarted. I've been bitten by that one before.
>
>    Hugo.
>
>> "btrfs fi df /" reports the following:
>>
>> Data, single: total=11.01GiB, used=10.58GiB
>> System, DUP: total=8.00MiB, used=16.00KiB
>> System, single: total=4.00MiB, used=0.00B
>> Metadata, DUP: total=1.00GiB, used=397.80MiB
>> Metadata, single: total=8.00MiB, used=0.00B
>> GlobalReserve, single: total=144.00MiB, used=0.00B
>>
>> "btrfs filesystem show /" gives:
>>
>> Label: none  uuid: 4ea4ac08-ff37-4b51-b1a3-d8b21fd43ddd
>>     Total devices 1 FS bytes used 10.97GiB
>>     devid    1 size 15.02GiB used 13.04GiB path /dev/sda6
>>
>> btrfs-progs v4.0
>>
>> "du --max-depth=1 -h -x" on / shows:
>>
>> 29M    ./etc
>> 0    ./media
>> 16M    ./bin
>> 354M    ./lib
>> 4.0K    ./lib64
>> 0    ./mnt
>> 160K    ./root
>> 12M    ./sbin
>> 0    ./srv
>> 4.0K    ./tmp
>> 3.1G    ./usr
>> 442M    ./var
>> 0    ./cdrom
>> 3.8M    ./lib32
>> 3.9G    .
>>
>> And of course df:
>>
>> /dev/sda6        16G   12G  2.5G  83% /
>> /dev/sda5       232M   53M  163M  25% /boot
>> /dev/sda7       104G   46G   57G  45% /home
>>
>> And mount:
>>
>> mount |grep sda
>> /dev/sda6 on / type btrfs
>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@)
>> /dev/sda5 on /boot type ext4 (rw,relatime,data=ordered)
>> /dev/sda7 on /home type btrfs
>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@home)
>>
>> uname -a
>> Linux ichor 4.2.0-18-generic #22-Ubuntu SMP Fri Nov 6 18:25:50 UTC
>> 2015 x86_64 x86_64 x86_64 GNU/Linux
>>
>> I can live with the situation, but recovering that space would be nice.
>
> --
> Hugo Mills             | Happiness is mandatory. Are you happy?
> hugo@... carfax.org.uk |
> http://carfax.org.uk/  |
> PGP: E2AB1DE4          |                                              Paranoia



-- 
http://brentonchapin.no-ip.biz

Re: free space is missing after dist upgrade on lzo compressed vol

[Timofey Titovets]

Ubuntu create snapshot before each release upgrade
sudo mount /dev/sda6 /mnt -o rw,subvol=/;
ls /mnt

2015-11-14 9:16 GMT+03:00 Brenton Chapin <bzipitidoo@gmail.com>:
> Thanks for the ideas.  Sadly, no snapshots, unless btrfs does that by
> default.  Never heard of snapper before.
>
> Don't see how open files could be a problem, since the computer has
> been rebooted several times.
>
> I wonder... could the distribution upgrade have moved all the old
> files into a hidden trash directory, rather than deleting them?  But
> du picks up hidden directories, I believe.  Doesn't seem like that
> could be it either.
>
> On Fri, Nov 13, 2015 at 4:38 PM, Hugo Mills <hugo@carfax.org.uk> wrote:
>> On Fri, Nov 13, 2015 at 04:33:23PM -0600, Brenton Chapin wrote:
>>> I was running Lubuntu 14.04 on btrfs with lzo compresssion on, with
>>> the following partition scheme:
>>>
>>> sda5   232M  /boot
>>> sda6   16G   /
>>> sda7   104G /home
>>>
>>> (sda5 is ext4)
>>>
>>> I did 2 distribution upgrades, one after the other, to 15.04, then
>>> 15.10, since the upgrade utility would not go directly to the latest
>>> version.  This process did a whole lot of reading and writing to the
>>> root volume of course.  Everything seems to be working, except most of
>>> the free space I had on sda6 is gone.  Was using about 4G, now df
>>> reports that the usage is 12G.  At first, I thought Lubuntu had not
>>> removed old files, but I can't find anything old left behind.  I began
>>> to suspect btrfs, and checking, find that du shows only 4G used on
>>> sda6.  Where'd the other 8G go?
>>
>>    Do you have snapshots? Are you running snapper, for example?
>>
>>    The other place that large amounts of space can go over an upgrade
>> is in orphans -- files that are deleted, but still held open by
>> processes, and which therefore can't be reclaimed until the process is
>> restarted. I've been bitten by that one before.
>>
>>    Hugo.
>>
>>> "btrfs fi df /" reports the following:
>>>
>>> Data, single: total=11.01GiB, used=10.58GiB
>>> System, DUP: total=8.00MiB, used=16.00KiB
>>> System, single: total=4.00MiB, used=0.00B
>>> Metadata, DUP: total=1.00GiB, used=397.80MiB
>>> Metadata, single: total=8.00MiB, used=0.00B
>>> GlobalReserve, single: total=144.00MiB, used=0.00B
>>>
>>> "btrfs filesystem show /" gives:
>>>
>>> Label: none  uuid: 4ea4ac08-ff37-4b51-b1a3-d8b21fd43ddd
>>>     Total devices 1 FS bytes used 10.97GiB
>>>     devid    1 size 15.02GiB used 13.04GiB path /dev/sda6
>>>
>>> btrfs-progs v4.0
>>>
>>> "du --max-depth=1 -h -x" on / shows:
>>>
>>> 29M    ./etc
>>> 0    ./media
>>> 16M    ./bin
>>> 354M    ./lib
>>> 4.0K    ./lib64
>>> 0    ./mnt
>>> 160K    ./root
>>> 12M    ./sbin
>>> 0    ./srv
>>> 4.0K    ./tmp
>>> 3.1G    ./usr
>>> 442M    ./var
>>> 0    ./cdrom
>>> 3.8M    ./lib32
>>> 3.9G    .
>>>
>>> And of course df:
>>>
>>> /dev/sda6        16G   12G  2.5G  83% /
>>> /dev/sda5       232M   53M  163M  25% /boot
>>> /dev/sda7       104G   46G   57G  45% /home
>>>
>>> And mount:
>>>
>>> mount |grep sda
>>> /dev/sda6 on / type btrfs
>>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@)
>>> /dev/sda5 on /boot type ext4 (rw,relatime,data=ordered)
>>> /dev/sda7 on /home type btrfs
>>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@home)
>>>
>>> uname -a
>>> Linux ichor 4.2.0-18-generic #22-Ubuntu SMP Fri Nov 6 18:25:50 UTC
>>> 2015 x86_64 x86_64 x86_64 GNU/Linux
>>>
>>> I can live with the situation, but recovering that space would be nice.
>>
>> --
>> Hugo Mills             | Happiness is mandatory. Are you happy?
>> hugo@... carfax.org.uk |
>> http://carfax.org.uk/  |
>> PGP: E2AB1DE4          |                                              Paranoia
>
>
>
> --
> http://brentonchapin.no-ip.biz
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html



-- 
Have a nice day,
Timofey.

Re: free space is missing after dist upgrade on lzo compressed vol

[Brenton Chapin]

Thanks, snapshots, or subvolumes, was it.  (I'm not clear on the
distinction between a snapshot and a subvolume.)  The 8G amount and
that I did 2 distribution upgrades was a clue.  When I searched for
info on btrfs and snapshots, I eventually found this command, with
these results:

btrfs subvolume list -p /
ID 257 gen 16615 parent 5 top level 5 path @
ID 262 gen 15857 parent 5 top level 5 path
@apt-snapshot-release-upgrade-vivid-2015-11-12_15:49:30
ID 266 gen 16544 parent 257 top level 257 path var/lib/machines
ID 268 gen 16203 parent 5 top level 5 path
@apt-snapshot-release-upgrade-wily-2015-11-13_04:10:00

Seems these subvolumes (snapshots?) are nowhere visible in the file
system.  Now I'm trying to figure out the correct commands to delete
them.  "btrfs subvolume delete @apt-snapshot..." gave "ERROR: error
accessing '@apt-snapshot...", while "btrfs sbuvolume show " on
variations of the name keep giving me "ERROR: finding real path for
'...', No such file or directory."  No luck so far.  What am I
missing?

On Sat, Nov 14, 2015 at 3:16 AM, Timofey Titovets <nefelim4ag@gmail.com> wrote:
> Ubuntu create snapshot before each release upgrade
> sudo mount /dev/sda6 /mnt -o rw,subvol=/;
> ls /mnt
>
> 2015-11-14 9:16 GMT+03:00 Brenton Chapin <bzipitidoo@gmail.com>:
>> Thanks for the ideas.  Sadly, no snapshots, unless btrfs does that by
>> default.  Never heard of snapper before.
>>
>> Don't see how open files could be a problem, since the computer has
>> been rebooted several times.
>>
>> I wonder... could the distribution upgrade have moved all the old
>> files into a hidden trash directory, rather than deleting them?  But
>> du picks up hidden directories, I believe.  Doesn't seem like that
>> could be it either.
>>
>> On Fri, Nov 13, 2015 at 4:38 PM, Hugo Mills <hugo@carfax.org.uk> wrote:
>>> On Fri, Nov 13, 2015 at 04:33:23PM -0600, Brenton Chapin wrote:
>>>> I was running Lubuntu 14.04 on btrfs with lzo compresssion on, with
>>>> the following partition scheme:
>>>>
>>>> sda5   232M  /boot
>>>> sda6   16G   /
>>>> sda7   104G /home
>>>>
>>>> (sda5 is ext4)
>>>>
>>>> I did 2 distribution upgrades, one after the other, to 15.04, then
>>>> 15.10, since the upgrade utility would not go directly to the latest
>>>> version.  This process did a whole lot of reading and writing to the
>>>> root volume of course.  Everything seems to be working, except most of
>>>> the free space I had on sda6 is gone.  Was using about 4G, now df
>>>> reports that the usage is 12G.  At first, I thought Lubuntu had not
>>>> removed old files, but I can't find anything old left behind.  I began
>>>> to suspect btrfs, and checking, find that du shows only 4G used on
>>>> sda6.  Where'd the other 8G go?
>>>
>>>    Do you have snapshots? Are you running snapper, for example?
>>>
>>>    The other place that large amounts of space can go over an upgrade
>>> is in orphans -- files that are deleted, but still held open by
>>> processes, and which therefore can't be reclaimed until the process is
>>> restarted. I've been bitten by that one before.
>>>
>>>    Hugo.
>>>
>>>> "btrfs fi df /" reports the following:
>>>>
>>>> Data, single: total=11.01GiB, used=10.58GiB
>>>> System, DUP: total=8.00MiB, used=16.00KiB
>>>> System, single: total=4.00MiB, used=0.00B
>>>> Metadata, DUP: total=1.00GiB, used=397.80MiB
>>>> Metadata, single: total=8.00MiB, used=0.00B
>>>> GlobalReserve, single: total=144.00MiB, used=0.00B
>>>>
>>>> "btrfs filesystem show /" gives:
>>>>
>>>> Label: none  uuid: 4ea4ac08-ff37-4b51-b1a3-d8b21fd43ddd
>>>>     Total devices 1 FS bytes used 10.97GiB
>>>>     devid    1 size 15.02GiB used 13.04GiB path /dev/sda6
>>>>
>>>> btrfs-progs v4.0
>>>>
>>>> "du --max-depth=1 -h -x" on / shows:
>>>>
>>>> 29M    ./etc
>>>> 0    ./media
>>>> 16M    ./bin
>>>> 354M    ./lib
>>>> 4.0K    ./lib64
>>>> 0    ./mnt
>>>> 160K    ./root
>>>> 12M    ./sbin
>>>> 0    ./srv
>>>> 4.0K    ./tmp
>>>> 3.1G    ./usr
>>>> 442M    ./var
>>>> 0    ./cdrom
>>>> 3.8M    ./lib32
>>>> 3.9G    .
>>>>
>>>> And of course df:
>>>>
>>>> /dev/sda6        16G   12G  2.5G  83% /
>>>> /dev/sda5       232M   53M  163M  25% /boot
>>>> /dev/sda7       104G   46G   57G  45% /home
>>>>
>>>> And mount:
>>>>
>>>> mount |grep sda
>>>> /dev/sda6 on / type btrfs
>>>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@)
>>>> /dev/sda5 on /boot type ext4 (rw,relatime,data=ordered)
>>>> /dev/sda7 on /home type btrfs
>>>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@home)
>>>>
>>>> uname -a
>>>> Linux ichor 4.2.0-18-generic #22-Ubuntu SMP Fri Nov 6 18:25:50 UTC
>>>> 2015 x86_64 x86_64 x86_64 GNU/Linux
>>>>
>>>> I can live with the situation, but recovering that space would be nice.
>>>
>>> --
>>> Hugo Mills             | Happiness is mandatory. Are you happy?
>>> hugo@... carfax.org.uk |
>>> http://carfax.org.uk/  |
>>> PGP: E2AB1DE4          |                                              Paranoia
>>
>>
>>
>> --
>> http://brentonchapin.no-ip.biz
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>
> --
> Have a nice day,
> Timofey.



-- 
http://brentonchapin.no-ip.biz

Re: free space is missing after dist upgrade on lzo compressed vol

[Hugo Mills]

[-- Attachment #1: Type: text/plain, Size: 5460 bytes --]

On Sat, Nov 21, 2015 at 12:32:12PM -0600, Brenton Chapin wrote:
> Thanks, snapshots, or subvolumes, was it.  (I'm not clear on the
> distinction between a snapshot and a subvolume.)

   A snapshot is just a subvolume that's initialised (via CoW copies)
with the contents of some other subvolume, rather than starting empty.

   Hugo.

>  The 8G amount and
> that I did 2 distribution upgrades was a clue.  When I searched for
> info on btrfs and snapshots, I eventually found this command, with
> these results:
> 
> btrfs subvolume list -p /
> ID 257 gen 16615 parent 5 top level 5 path @
> ID 262 gen 15857 parent 5 top level 5 path
> @apt-snapshot-release-upgrade-vivid-2015-11-12_15:49:30
> ID 266 gen 16544 parent 257 top level 257 path var/lib/machines
> ID 268 gen 16203 parent 5 top level 5 path
> @apt-snapshot-release-upgrade-wily-2015-11-13_04:10:00
> 
> Seems these subvolumes (snapshots?) are nowhere visible in the file
> system.  Now I'm trying to figure out the correct commands to delete
> them.  "btrfs subvolume delete @apt-snapshot..." gave "ERROR: error
> accessing '@apt-snapshot...", while "btrfs sbuvolume show " on
> variations of the name keep giving me "ERROR: finding real path for
> '...', No such file or directory."  No luck so far.  What am I
> missing?
> 
> On Sat, Nov 14, 2015 at 3:16 AM, Timofey Titovets <nefelim4ag@gmail.com> wrote:
> > Ubuntu create snapshot before each release upgrade
> > sudo mount /dev/sda6 /mnt -o rw,subvol=/;
> > ls /mnt
> >
> > 2015-11-14 9:16 GMT+03:00 Brenton Chapin <bzipitidoo@gmail.com>:
> >> Thanks for the ideas.  Sadly, no snapshots, unless btrfs does that by
> >> default.  Never heard of snapper before.
> >>
> >> Don't see how open files could be a problem, since the computer has
> >> been rebooted several times.
> >>
> >> I wonder... could the distribution upgrade have moved all the old
> >> files into a hidden trash directory, rather than deleting them?  But
> >> du picks up hidden directories, I believe.  Doesn't seem like that
> >> could be it either.
> >>
> >> On Fri, Nov 13, 2015 at 4:38 PM, Hugo Mills <hugo@carfax.org.uk> wrote:
> >>> On Fri, Nov 13, 2015 at 04:33:23PM -0600, Brenton Chapin wrote:
> >>>> I was running Lubuntu 14.04 on btrfs with lzo compresssion on, with
> >>>> the following partition scheme:
> >>>>
> >>>> sda5   232M  /boot
> >>>> sda6   16G   /
> >>>> sda7   104G /home
> >>>>
> >>>> (sda5 is ext4)
> >>>>
> >>>> I did 2 distribution upgrades, one after the other, to 15.04, then
> >>>> 15.10, since the upgrade utility would not go directly to the latest
> >>>> version.  This process did a whole lot of reading and writing to the
> >>>> root volume of course.  Everything seems to be working, except most of
> >>>> the free space I had on sda6 is gone.  Was using about 4G, now df
> >>>> reports that the usage is 12G.  At first, I thought Lubuntu had not
> >>>> removed old files, but I can't find anything old left behind.  I began
> >>>> to suspect btrfs, and checking, find that du shows only 4G used on
> >>>> sda6.  Where'd the other 8G go?
> >>>
> >>>    Do you have snapshots? Are you running snapper, for example?
> >>>
> >>>    The other place that large amounts of space can go over an upgrade
> >>> is in orphans -- files that are deleted, but still held open by
> >>> processes, and which therefore can't be reclaimed until the process is
> >>> restarted. I've been bitten by that one before.
> >>>
> >>>    Hugo.
> >>>
> >>>> "btrfs fi df /" reports the following:
> >>>>
> >>>> Data, single: total=11.01GiB, used=10.58GiB
> >>>> System, DUP: total=8.00MiB, used=16.00KiB
> >>>> System, single: total=4.00MiB, used=0.00B
> >>>> Metadata, DUP: total=1.00GiB, used=397.80MiB
> >>>> Metadata, single: total=8.00MiB, used=0.00B
> >>>> GlobalReserve, single: total=144.00MiB, used=0.00B
> >>>>
> >>>> "btrfs filesystem show /" gives:
> >>>>
> >>>> Label: none  uuid: 4ea4ac08-ff37-4b51-b1a3-d8b21fd43ddd
> >>>>     Total devices 1 FS bytes used 10.97GiB
> >>>>     devid    1 size 15.02GiB used 13.04GiB path /dev/sda6
> >>>>
> >>>> btrfs-progs v4.0
> >>>>
> >>>> "du --max-depth=1 -h -x" on / shows:
> >>>>
> >>>> 29M    ./etc
> >>>> 0    ./media
> >>>> 16M    ./bin
> >>>> 354M    ./lib
> >>>> 4.0K    ./lib64
> >>>> 0    ./mnt
> >>>> 160K    ./root
> >>>> 12M    ./sbin
> >>>> 0    ./srv
> >>>> 4.0K    ./tmp
> >>>> 3.1G    ./usr
> >>>> 442M    ./var
> >>>> 0    ./cdrom
> >>>> 3.8M    ./lib32
> >>>> 3.9G    .
> >>>>
> >>>> And of course df:
> >>>>
> >>>> /dev/sda6        16G   12G  2.5G  83% /
> >>>> /dev/sda5       232M   53M  163M  25% /boot
> >>>> /dev/sda7       104G   46G   57G  45% /home
> >>>>
> >>>> And mount:
> >>>>
> >>>> mount |grep sda
> >>>> /dev/sda6 on / type btrfs
> >>>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@)
> >>>> /dev/sda5 on /boot type ext4 (rw,relatime,data=ordered)
> >>>> /dev/sda7 on /home type btrfs
> >>>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@home)
> >>>>
> >>>> uname -a
> >>>> Linux ichor 4.2.0-18-generic #22-Ubuntu SMP Fri Nov 6 18:25:50 UTC
> >>>> 2015 x86_64 x86_64 x86_64 GNU/Linux
> >>>>
> >>>> I can live with the situation, but recovering that space would be nice.
> >>>

-- 
Hugo Mills             | Le Corbusier's plan for improving Paris involved the
hugo@... carfax.org.uk | assassination of the city, and its rebirth as tower
http://carfax.org.uk/  | blocks.
PGP: E2AB1DE4          |                   Robert Hughes, The Shock of the New

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Re: free space is missing after dist upgrade on lzo compressed vol

[Duncan]

Brenton Chapin posted on Sat, 21 Nov 2015 12:32:12 -0600 as excerpted:

> Thanks, snapshots, or subvolumes, was it.  (I'm not clear on the
> distinction between a snapshot and a subvolume.)

As Hugo says much more briefly, snapshots are a special kind of 
subvolume.  These are normally (copy-on-write, aka cow, based) 
"snapshots" of another subvolume at a the point they were taken, 
containing the same data, etc.  Snapshots can be read-only, in which case 
they lock in what the snapshotted subvolume looked like at that time, or 
writable, just like normal subvolumes, in which case they start out 
looking like the subvolume they snapshotted at that point in time, but 
both the original subvolume and its writable snapshot can be written to, 
so one or both can diverge from the "picture" that was taken by the 
snapshot.

Subvolumes (and thus snapshots, since snapshots are a special case of 
subvolume), meanwhile, look and work almost like directories, except they 
have a few extra features that normal directories don't have, the biggest 
of which is that subvolumes can be mounted separately, as if they were 
their own filesystems.  This is actually what's happening below, as it's 
not the "root" subvolume that's actually mounted at /, but rather, a 
subvolume below the root subvolume.  Knowing that should help make sense 
of the subvolume list output, below, and explains why you don't see the 
subvolumes in the filesystem, as what's mounted at / isn't actually the 
root subvolume, but a subvolume nested within the root subvolume.

More on that below, but while we're talking about subvolume features, let 
me repeat something I said above, now that you have a bit more context to 
put it in.  Snapshots are taken of specific subvolumes (again, if it 
helps, think subdirs), NOT of the whole filesystem including all 
subvolumes.  As such, snapshots stop at subvolume boundaries.  If for 
instance you take a snapshot of the root subvolume (ID 5 in the listing 
below, *NOT* the nested subvolume below it that happens to be mounted
at /), you get a picture/snapshot of only what's directly in it, not 
what's in subvolumes nested beneath it.  Nested subvolumes are 
snapshotted separately.

> btrfs subvolume list -p /
> ID 257 gen 16615 parent 5 top level 5 path @
> ID 262 gen 15857 parent 5 top level 5 path
> @apt-snapshot-release-upgrade-vivid-2015-11-12_15:49:30
> ID 266 gen 16544 parent 257 top level 257 path
> var/lib/machines
> ID 268 gen 16203 parent 5 top level 5 path
> @apt-snapshot-release-upgrade-wily-2015-11-13_04:10:00
> 
> Seems these subvolumes (snapshots?) are nowhere visible in the file
> system.  Now I'm trying to figure out the correct commands to delete
> them.  "btrfs subvolume delete @apt-snapshot..." gave "ERROR: error
> accessing '@apt-snapshot...", while "btrfs sbuvolume show " on
> variations of the name keep giving me "ERROR: finding real path for
> '...', No such file or directory."  No luck so far.  What am I missing?

As I said above, you won't see these subvolumes (including snapshots) 
visible in the filesystem, because what you have mounted at / is not the 
root level (ID 5) subvolume, but rather, a subvolume nested within it.

Visualizing the above listing as a tree, you have...

+-+--       ID 5  root subvolume, always ID 5 (not listed)
  |
  +-+--   ID 257  @ (this is what is mounted at /)
  | |
  | +--   ID 266	(@/)var/lib/machines (systemd generated)
  |
  +--     ID 262 @apt-snapshot-release-upgrade-vivid...
  |
  +--     ID 268 @apt-snapshot-release-upgrade-wily...

As mentioned, it's ID 257, @, that's mounted at /.  Your 4.2 kernel is 
actually new enough to print this information in the mount output, and 
indeed, from the mount output you posted upthread:

>>>>> /dev/sda6 on / type btrfs
>>>>> (rw,relatime,compress=lzo,space_cache,subvolid=257,subvol=/@)

See that subvolid=257,subvol=/@ ?  That's the same ID 257 @ as shown in 
your subvolume list, and as I diagrammed in the tree layout.

IDs 262 and 268 are snapshots of the state of ID 257 @, at the time you 
did the upgrades.  ID 5 is of course the root subvolume, in which the 
others are nested, and ID 257 @, has ID 266 nested within it.  Of course 
this information can be easily seen from the tree layout I did, but it's 
there in the listing as well, with the parent/top-level ID in the listing 
being the direct parent subvolume.

OK, so how do you delete those snapshots and recover the space they claim?

As with normal directories in filesystems, to work with subvolumes/
snapshots in btrfs, you need a subvolume from which they're descended 
mounted.

Since ID 257 (@) is mounted, ID 266, var/lib/machines, nested within it, 
is visible in its tree, and for most purposes will look and behave like 
an ordinary directory, except that you won't be able to rmdir it, because 
it's actually a subvolume.  As long as it's not actually mounted as its 
own subvolume, however, you could btrfs subvolume delete it, if you 
wanted to.

But the two snapshots, ID 262 and 268, are not within the mounted tree 
and you can't directly work with them as a result, tho you _can_ btrfs 
subvolume list them, as you did.  To work with them, in this case, to 
btrfs subvolume delete them, you'll need to mount their parent subvolume 
somewhere.

Tho here's where I start going out beyond my own personal working 
knowledge, as I neither run Ubuntu (I'm a Gentooer), so don't know what 
specific mount points it might provide for that, nor do I actually use 
the btrfs subvolumes/snapshots features here, tho I did play with them 
just a bit when I was first setting things up here, before deciding they 
didn't actually fit my use-case very well, and my life was simpler 
without trying to use them.  So while I can read the btrfs-subvolume 
manpage and the subvolume documentation on the btrfs wiki, so can you, 
and with limited personal experience, I don't have the benefit of that 
experience to pass on many hints or warnings based on it.  So the actual 
command details are going to be a bit vague/theoretical/handwavy.

But here what I'd do would be:

1) Create a mountpoint for the purpose, say /mnt/rootfsrootsubvol/

(That lets you create other mountpoints, say /mnt/homefsrootsubvol/, if 
you want to do the same thing for your home filesystem, since I noticed 
in your mount output that it's a separate btrfs, also using subvolumes.)

2) (Optional)  Create an fstab entry with my desired device, mount point 
and mount options, specifically including subvolid=5, and probably noauto, 
unless you want it mounted all the time, something like this:

/dev/sda6 /mnt/rootfsrootsubvol btrfs subvolid=5,noauto

3) Mount the root subvolume, either using the options from the fstab 
entry you created in step 2, or manually adding the -o subvolid=5 option.

4) /Now/ do your deletion using the path, much as you'd delete a 
directory, except of course using btrfs subvolume delete instead of rmdir 
or rm -r.

(Obviously untested because as I said I don't use the subvolume 
functionality here, but /something/ like this...)

btrfs subvolume delete [-c|-C] /mnt/rootfsrootsubvol/@apt-snapshot...

Hint: Use tab-completion to avoid having to type in the whole path. =:^)

The -c/-C options are described in the manpage, but...  without them, the 
command will return, but btrfs will still be working on doing the actual 
delete in the background.  So you get a prompt back pretty fast, but 
because the delete will be ongoing, you won't see the full result in your 
btrfs fi df/show/usage or in normal df, for awhile.  If you prefer that 
the delete command not return until the delete is actually done, use the
-c option.  If you're deleting several snapshots/subvolumes at once, -c 
will delete them all and then do a commit before returning, while -C will 
do a commit after each one, of course returning only after the last one.  
Thus, with these options the command will continue running for longer, 
but when it /does/ return, you should be able to see the properly final 
subvolume deletion results in your btrfs filesystem show/df/usage 
commands and in regular df.

5) Don't forget to umount the root subvolume, again. =:^)


Tip/Recommendation:  Don't keep the root subvolume mounted all the time.  
Mount it to work with subvolumes.  Unmount it when you're done working 
with them.  Besides being generally good practice, there's a security 
dimension to consider.  Snapshots in particular will have old copies of 
various executables and libraries around, some of which will be still 
vulnerable versions of executables and libraries that have had security 
updates since then.  Should someone with ill intent get access to your 
system and these security-vulnerable executables and libraries are 
accessible via mounted snapshot or root subvolume, these old binaries 
with known security issues could well make it far easier for them to get 
root access than it would be were these old snapshots not accessible 
because neither they nor the root subvolume are mounted.

Of course keeping the root subvolume unmounted keeps you or others from 
accidentally (or deliberately, as an attack) deleting subvolumes and 
snapshots not immediately nested in your working system, as well.

So just keep the root subvolume unmounted unless you're actually working 
with it, for much the same reasons you don't run as root unless you're 
actually doing something that needs it. =:^)

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman