Filesystem full, but df says not.

[Rodney W. Grimes]

> On Thu, Dec 14, 2017 at 11:10:45AM -0800, Mark Millard wrote:
> > On 2017-Dec-14, at 11:00 AM, bob prohaska <fbsd at www.zefox.net> wrote:
> > 
> > 
> > > An rpi2 running -current reported errors during boot like this on the
> > > serial console after a graceful reboot:
> > > 
> > > UFS /dev/ufs/rootfs (/) cylinder checksum failed: cg 0, cgp: 0x4c0a5f41 != bp: 0x38b82866
> > > UFS /dev/ufs/rootfs (/) cylinder checksum failed: cg 3, cgp: 0x58e2c1f5 != bp: 0x903c297
> > > UFS /dev/ufs/rootfs (/) cylinder checksum failed: cg 0, cgp: 0x4c0a5f41 != bp: 0x38b82866
> > 
> > Believe the above low-level messages.
> > 
> > > /: write failed, filesystem is full
> > > cp: /etc/motd: No space left on device
> > 
> > My guess:
> > 
> > Other places likely translate the more detailed error
> > classification to more generic classifications that
> > hopefully result in an appropriate handling of the issue
> > but is otherwise not necessarily correct.
> > 
> > In other words: do not believe the later related messages
> > in all its detail.
> > 
> > > .
> > > Mounting late filesystems:.
> > > Dec 14 10:08:56 www kernel: pid 1394 (cp), uid 0 inumber 53912 on /: filesystem full
> > > 
> > > Root is on the microSD card, /usr /var /tmp and swap are on usb flash.
> > > 
> > > Nevertheless, it reached multi-user and allowed me  to  ssh in and run df,
> > > which reported
> > > Filesystem             1K-blocks     Used    Avail Capacity  Mounted on
> > > /dev/ufs/rootfs          1473116   479936   875332    35%    /
> > > devfs                          1        1        0   100%    /dev
> > > /dev/msdosfs/MSDOSBOOT     51140     7588    43552    15%    /boot/msdos
> > > /dev/da0e               52221244 28697844 19345704    60%    /usr
> > > /dev/da0d                3044988   517860  2283532    18%    /tmp
> > > /dev/da0a                2031132   122868  1745776     7%    /var
> > 
> > This activity probably did not depend on the bad cylinder
> > checksums.
> > 
> > > Still, any activity that wrote to disk repeated the filesystem full error.
> > > 
> > > This happened with three different kernels, dating Dec 12, 7 and Aug 26.
> > > Running fsck -fy once in single user didn't seem to help, although it 
> > > finished without obvious errors. Running fsck -fy repeatedly in single-user 
> > > seems to have cleared the error, but it's a surprising development.
> > 
> > 
> 
> Is there any user utility more rigorous than fsck to inspect the filesystem?
> 
> The machine is now building world without obvious distress.
> 
> Thanks for reading!

I should of pointed out that to clear up the bad CG checksum you
should run a fsck -f on the device and answer Y, this is NOT
the same as running fsck -fy, see a modern man fsck.

I also believe Kirk is working on some thing that should remove this
annoying problem.

-- 
Rod Grimes                                                 rgrimes at freebsd.org