Error: Disk space is too low! I am trying to run bitcoind on a raspberrypi.
I started by starting bitcoind on my laptop,downloading and verifying the blockchain. So far so good, bitcoind works as expected.
Then I set prune=600 in bitcoin.conf, and it pruned as expected.
Then I moved the datafiles to my raspberrypi (the whole /bitcoin directory ).
The SD card has ~7Gb of storage.  3.5Gb was available, including the /bitcoin dir.
There was a pause of some days or weeks, so I lack the blocks in between times.
When I ran bitcoind it gave me the 'Error Disk space is too low' report, and the SD card is full
root@mybox:/home/rshn# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root       7.3G  7.0G     0 100% /

The bitcoind log seems to indicate that it is downloading from the earliest blocks
2021-05-06T08:09:10Z
UpdateTip: new best=000000000000065c0819853ac71bdda8518706b8942f6540079ad079e2dea6e4 
height=193539 version=0x00000002 log2_work=68.525890 tx=5868863 
date='2012-08-12T12:29:56Z' progress=0.009181 cache=261.0MiB(2279817txo)

The blocks dir indicates that there are about 460Mb of data.
root@mybox:/home/rshn/bitcoin/blocks# ls -l
total 460068
-rw------- 1 rshn rshn 134212156 Apr 30 13:07 blk00002.dat
-rw------- 1 rshn rshn 134205043 Apr 30 13:08 blk00003.dat
-rw------- 1 rshn rshn 134191619 Apr 30 13:10 blk00004.dat
-rw------- 1 rshn rshn  16777216 Apr 30 13:10 blk00005.dat
drwx------ 2 rshn rshn      4096 Apr 30 13:10 index
-rw------- 1 rshn rshn  16271929 Apr 30 13:07 rev00002.dat
-rw------- 1 rshn rshn  16501235 Apr 30 13:08 rev00003.dat
-rw------- 1 rshn rshn  16826540 Apr 30 13:10 rev00004.dat
-rw------- 1 rshn rshn   2097152 Apr 30 13:10 rev00005.dat

How do I run the pruned node in these circs?  Thank you.
The answer was
The bitcoind client/executable was owned by user rshn.
I started the bitcoind client from a terminal as root user.
bitcoind treated the process as a new install because the owner was different.
bitcoind started downloading the full blockchain,
hence I ran out of disk space quite quickly!
TIL  start the bitcoind client logged in as the owner of the executable.