Connection to xx.xx.xx.xx closed by remote host during rsync backup

Question

I have 2 web servers. Let's call them local and remote just for simplicity. Local: I've only ftp and cron access, Remote: ssh/ftp

I wrote a simple backup script, which tars the files and then sends them to the remote server. (called in cron) Local server is added in ~/.ssh/authorized_keys on the remote server to make connection without using password.

cd $FILES_TO_BACKUP_DIR
for dir in */
do
    base=$(basename "$dir")
    tar -czpf "$BACKUP_DIR/${base}-$DATE.tar.gz" "$dir"
    rsync -az -e "ssh -p $REMOTE_HOST_PORT -i $KEY_PATH" $BACKUP_DIR $REMOTE_HOST_ADDRESS:$REMOTE_BACKUP_DIR
    rm $BACKUP_DIR/${base}-$DATE.tar.gz
done

I think it works fine - the files are appearing on the remote server. I've compared sizes of all files and checksums of some of them. Everything matches.

However I'm not sure about this message: Connection to xxx.xxx.xxx.xxx closed by remote host. It appears different number of times each time the script is called.

For the testing purposes, I copy around 20 tars.

I've added set -x at the beginning of the script to show each line as it's executing.

Here is part of the log:

./backup.sh
+ cd /home/tobackup/
+ for dir in '*/'
++ basename lgsm/
+ base=lgsm
+ tar -czpf /home/test/_backups/backups-tmp/lgsm-09-01-2020.tar.gz lgsm/
+ rsync -vaz -e 'ssh -p PORT' /home/test/_backups/backups-tmp USER@IP:/home/backups_test/_backups/backups
sending incremental file list
backups-tmp/
backups-tmp/lgsm-09-01-2020.tar.gz
backups-tmp/serverfiles-09-01-2020.tar.gz
Connection to IP closed by remote host.

sent 237,480,856 bytes  received 10,786 bytes  6,168,614.08 bytes/sec
total size is 241,069,740  speedup is 1.02
+ rm /home/test/_backups/backups-tmp/lgsm-09-01-2020.tar.gz
+ for dir in '*/'
++ basename log/
+ base=log
+ tar -czpf /home/test/_backups/backups-tmp/log-09-01-2020.tar.gz log/
+ rsync -vaz -e 'ssh -p PORT' /home/test/_backups/backups-tmp USER@IP:/home/backups_test/_backups/backups
sending incremental file list
backups-tmp/
backups-tmp/log-09-01-2020.tar.gz
Connection to IP closed by remote host.

sent 900 bytes  received 81 bytes  654.00 bytes/sec
total size is 237,899,887  speedup is 242,507.53
+ rm /home/test/_backups/backups-tmp/log-09-01-2020.tar.gz
+ for dir in '*/'
++ basename serverfiles/
+ base=serverfiles
+ tar -czpf /home/test/_backups/backups-tmp/serverfiles-09-01-2020.tar.gz serverfiles/

I'm curious why this is happening and if it's possible, how can I prevent such behavior. (If it's not important as it seems I'd like to hide the message, but keep potential other error messages. I've tried using rsync -q to suppress the message,)

Answer 1

I've compared described behavior between 5 different servers and only the connection with one particular server has this issue.

After checking with md5 checksum I'm sure that files are identical.

As the warning does not affect anything I've decided to suppress the message.
For now, I've modified the backup script on the server so in case of any use of ssh, it logs output to the file first by: >> $BACKUP_LOGS_FILE 2>&1 at the end of the command.

At the very end of the script I'm using grep to filter out the output: grep -v 'Connection to xxx.xxx.xxx.xxx closed by remote host.' $BACKUP_LOGS_FILE

However, if anyone has any explanation what can be causing this, feel free to add your answer.