The volume data encountered an error and was made read-only. It is recommended to backup your data.

Fiddled with it a bit, and figured out how to ssh as root.  Oof madone, I really need to RTFM (but that's another story..)

I think I know what to do here, but I just want to make sure..  when I run the command:

btrfs rescue zero-log /dev/md127

I get an error:

ERROR: /dev/md127 is currently mounted

I'm thinking I should do:

umount /dev/md127

but, I'm worried about doing something irreversably bad.

umount won't work if the device is busy (has any open files) - so that command might fail.  It's worth a try though.  Make sure you aren't in a folder of the data volume when you try it - that will definitely fail.

The other option is to boot up the NAS in tech support mode, and access the linux command line with telnet.  We can give you instructions on how to do that if you can't get the umount to work.

So.. the umount command seems to complete without error (no output to the terminal at all).. but doesn't appear to actually do anything.. since the btrfs rescue command then fails in the exact same way..

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as_ wrote:

So.. the umount command seems to complete without error (no output to the terminal at all).. but doesn't appear to actually do anything.. since the btrfs rescue command then fails in the exact same way..

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Have you tried looking at the volume with the ls command after you ran umount?

ls -l /dev:

(truncated output)
brw-rw---- 1 root disk      9, 127 Mar 23  2021 md127
(truncated output)

cd /dev/md127:

-bash: cd: md127: Not a directory

You aren't looking at the data volume, you are looking at the device.

The default data volume name is data.  So ls -als /data

Ah.  That's one of those things I don't really understand about *nix systems in general..

So /data cursory glance looks like my files are still accessible by that path.

But now.. and I don't know whether this was because of something I did or not..

:~#umount /dev/md127
umount: /apps: target is busy
(In some cases useful info about processes that
use the device is found by lsof(8) or fuser(1).)

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as_ wrote:

Ah.  That's one of those things I don't really understand about *nix systems in general..

 

---

sda, sdb, ... (/dev/sda, ...) are the physical disks

md127 is the RAID array (which is a virtual disk)

data is the file system that is on the virtual disk.

umount will accept either the device (/dev/md127) or the file system - it's a bit unusual in that regard.

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as_ wrote:

So /data cursory glance looks like my files are still accessible by that path.

But now.. and I don't know whether this was because of something I did or not..

:~#umount /dev/md127
umount: /apps: target is busy
(In some cases useful info about processes that
use the device is found by lsof(8) or fuser(1).)

 

---

/apps is actually a linux mount point - the folder on the data volume (/data/.apps).  

Try umount /data Then check if you can see folders in /data and /apps.

If that doesn't work you'll need to reboot in tech support mode.

:~# umount /data
umount: /data  target is busy
        (In some cases useful info about processes that
         use the device is found by lsof(8) or fuser(1).)
:~# fuser -u /data
/data                21509c(root) 21520c(root)
:~# ps -ef | grep 215
root     21509  2009  0 Nov23 ?        00:00:01 /usr/sbin/smbd --foreground --no-process-group
root     21520  2009  0 Nov23 ?        00:00:00 /usr/sbin/smbd --foreground --no-process-group

Would shutting off the SMB service help here?  Or is that a bad idea?

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as_ wrote:
Would shutting off the SMB service help here?  Or is that a bad idea?

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It might, but likely there are other processes running that will also get in the way.  I think it's best to use tech support mode. 

You do that using the instructions on page 28 here: https://www.downloads.netgear.com/files/GDC/RNDU2000/ReadyNAS_Ultra_UltraPlus_NVX_Pro_HW_en_8July11.pdf

You'll need to access the linux CLI using telnet instead of ssh.  If you use Windows, then one useful tool for that is putty (which can be downloaded from here: https://www.chiark.greenend.org.uk/~sgtatham/putty/latest.html )

The login for tech support mode is root, the password is infr8ntdebug

Once in, enter this:

# rnutil chroot
# btrfs device scan

At this point the data volume is unmounted, so you can try your btrfs commands.

If you want to try mount the volume in tech support mode later on, then enter this:

# mount /dev/md127 /data

This is read/write.  If it fails, you could confirm that you can still boot up read-only with

# mount -o ro /dev/md127 /data

When done you can enter

# sync

to make sure everything is written to the disks and then reboot.