My Pi 2 has quit saving files after a power reset.

Check and see if the partitions are mounted read only for some reason.  Use the command  "mount" (minus the quote marks) and look for (ro) at the end of any of the lines in the output.

The very last line has '...flash,errors=remount-ro,...'.

I don't see any errors.

It sounds like that for some reason at least one partition is being mounted read-only.  Without the full output of the command it is difficult to diagnose further.  Try running "dmesg" and look for errors there, also look in /var/log/messages for any error messages.

---Edit---

This is not the issue, as Roger Wolff pointed out, if the file system went read-only your process should throw an error and your editor would not let you save the file

It sounds like that for some reason at least one partition is being mounted read-only.  Without the full output of the command it is difficult to diagnose further.  Try running "dmesg" and look for errors there, also look in /var/log/messages for any error messages.

---Edit---

This is not the issue, as Roger Wolff pointed out, if the file system went read-only your process should throw an error and your editor would not let you save the file

Again... The process triggering the error would not be getting an error. But all subsequent writes would immediately fail with read-only file system.

I created a test read-only filesystem. When I edit a file with nano I get the following status message:

[ Warning: Modifying a file which is not locked, check directory permission? ]

Then when I try to exit and save the file, I get:

[ Error writing test.txt: Read-only file system ]

and nano refuses to exit. If your home dir would remount readonly due to errors you'd notice it.

Good point.  I have seen file systems go read only that didn't impact home directories.  It depends on the layout of the SD card, then again, on a Pi it is probably just one big file system on the SD card.  I was thinking in the mind set of a large hard drive with separate partitions for home, boot, var, etc, and should have looked closer at his df output.

Part of /var/log/messages.  From what I can tell, this is when the problem started.  The Pi is used as a fixed point controller and server.  It normally does not get power cycled.  All data and program changes made since July is gone.

Jul  4 06:25:07 raspberrypib rsyslogd: [origin software="rsyslogd" swVersion="8.4.2" x-pid="463" x-info="http://www.rsyslog.com"] rsyslogd was HUPed

Jul 5 02:12:03 raspberrypib rsyslogd-2007: action 'action 17' suspended, next retry is Tue Jul 5 02:12:33 2016 [try http://www.rsyslog.com/e/2007 ]

Jul  5 02:17:01 raspberrypib rsyslogd-2007: action 'action 17' suspended, next retry is Tue Jul  5 02:17:31 2016 [try http://www.rsyslog.com/e/2007 ]

This 'action 17' message is repeated many times.

If, indeed that is the day the "trouble" started, then that is a consequence of "something being wrong" and not the cause.

IF your filesystem has indeed become read-only, then rsyslog could be failing because it is refused access to writing the logfiles.

It is annoying that you made it sound that the pi was a workstation where YOU were editing and saving files, while now we learn that it is some sort of server.

Anway, if you do:

echo hi > hi.txt

what happens?

and then

cat hi.txt

And what does "mount" say? You have a root filesystem and an USB disk. Which one is not saving things? Or both?

I do save files on the Pi.  Its normal operation is allowing internet access to my control system.  That works.  I discovered the no save issue when I was writing a new application for the remote access.  Excuse me for annoying you.

I can save to the USB.  I always back up data and files to a USB.  The root system is not saving on non volatile memory.  The hi.txt file was created and displayed when I typed cat hi.txt.  After I rebooted the Pi, " No such file or directory".

I can create, edit and save files.  All the files operate normally, until I reboot or shutdown, then the files are gone.  The files are only being saved to non volatile memory.  It does not matter how I save the files, created via the server, remote connect to the Pi or from the keyboard.

I pulled the micro SD card and put it in my W10 computer.  I tried to create a file on the card. I received no errors, however the file was not created.  I tried to format the card/ W10, but received an error.  I tried to delete all files.  Looked like it worked. I removed and reinserted the card. All files were back.

Conclusion; micro SD card failure.

I replaced the micro SD card. Installed Raspbian-Pixel. Normal operation. Issue resolved.

Micro SD Card Write Protected? - [Solved] - Storage indicates sometimes the card has an error and will write protect itself to preserve the information. Check with the manufacturer for a utility that might resolve the card problem.

Clem