Currently running Leap 42.2 on Virtual Box with a 10G btrfs / volume *without*
snapshots. I have ~3.5G free space on / but installing latest Linux kernel
fails with "no space left on device":

linux-vpvz:/var/log # zypper up
Loading repository data...
Reading installed packages...

The following 2 items are locked and will not be changed by any action:
 Available:
  virtualbox-guest-kmp-default virtualbox-guest-x11

The following NEW package is going to be installed:
  kernel-default-4.4.73-18.17.1

1 new package to install.
Overall download size: 0 B. Already cached: 50.4 MiB. After the operation,
additional 238.0 MiB will be used.
Continue? [y/n/...? shows all options] (y): y
In cache kernel-default-4.4.73-18.17.1.x86_64.rpm                       (1/1), 
50.4 MiB (238.0 MiB unpacked)
Checking for file conflicts:
..........................................................................[done]
(1/1) Installing: kernel-default-4.4.73-18.17.1.x86_64
...............................................[error]
Installation of kernel-default-4.4.73-18.17.1.x86_64 failed:
Error: Subprocess failed. Error: RPM failed: error: unpacking of archive failed
on file
/lib/modules/4.4.73-18.17-default/kernel/net/netfilter/nf_conntrack_netlink.ko:
cpio: rename failed - No space left on device
error: kernel-default-4.4.73-18.17.1.x86_64: install failed

Abort, retry, ignore? [a/r/i] (a): i


linux-vpvz:/var/log # df -m /
Filesystem     1M-blocks  Used Available Use% Mounted on
/dev/sda2           9738  5918      3426  64% /
linux-vpvz:/var/log # btrfs fi show
Label: none  uuid: 2c89d0bf-a858-4378-a99b-bc58e86902ca
        Total devices 1 FS bytes used 5.51GiB
        devid    1 size 9.51GiB used 6.54GiB path /dev/sda2


linux-vpvz:/var/log # snapper list
The config 'root' does not exist. Likely snapper is not configured.
See 'man snapper' for further instructions.


linux-vpvz:/var/log # btrfs subvol list /
ID 257 gen 9354 top level 5 path @
ID 258 gen 8925 top level 257 path boot/grub2/i386-pc
ID 259 gen 8925 top level 257 path boot/grub2/x86_64-efi
ID 260 gen 9354 top level 257 path home
ID 261 gen 9348 top level 257 path opt
ID 262 gen 9348 top level 257 path srv
ID 263 gen 9348 top level 257 path tmp
ID 264 gen 9348 top level 257 path usr/local
ID 265 gen 9354 top level 257 path var/cache
ID 266 gen 8925 top level 257 path var/crash
ID 267 gen 8925 top level 257 path var/lib/libvirt/images
ID 268 gen 8925 top level 257 path var/lib/machines
ID 269 gen 8925 top level 257 path var/lib/mailman
ID 270 gen 8925 top level 257 path var/lib/mariadb
ID 271 gen 8925 top level 257 path var/lib/mysql
ID 272 gen 8925 top level 257 path var/lib/named
ID 273 gen 8925 top level 257 path var/lib/pgsql
ID 274 gen 9354 top level 257 path var/log
ID 275 gen 8925 top level 257 path var/opt
ID 276 gen 9354 top level 257 path var/spool
ID 277 gen 9354 top level 257 path var/tmp


linux-vpvz:/var/log # btrfs fi df /
Data, single: total=5.73GiB, used=5.30GiB
System, DUP: total=32.00MiB, used=16.00KiB
Metadata, DUP: total=384.00MiB, used=215.78MiB
GlobalReserve, single: total=16.34MiB, used=0.00B


Also, I ran this command before, to ensure minimal meta data usage:

for NN in $(seq 0 32); do btrfs balance start -v -dusage=$NN -musage=$NN /;
done