→ root hadoop fs -getmerge txt rootsumtxtgetmerge hadooptxt No such file or directory

This error suggests that there is no file named "hadoop.txt" in the root directory of Hadoop. You may need to check the spelling of the file name or the location where the files are stored. Additionally, you can try running the command without specifying the file extension, like this:

root hadoop fs -getmerge /* /root/sum.txt

This will merge all files in the root directory of Hadoop and save the output to "/root/sum.txt".