why is the `tcgetattr` error seen when ssh is used for dumping the backup file on another server?
I want to dump a tables backup on another server and I am using ssh for doing it. when I run the below command, it gives an error but dump file is copied to destination.
mysqldump -u username -ppassword dbname tablename | ssh -t -t servers_username@domain_name 'cat > /tmp/bckp.sql';
tcgetattr: Invalid argument
If I press CTRL+c then it appends error message with Killed by signal 2.
Why is this error?
Answer
I've seen this error when forcing pseudo-terminal allocation using ssh -t -t or ssh -tt.
The tcgetattr function is used to look up the attributes of the pseudoterminal represented by a file descriptor; it takes a file descriptor and a pointer to a termios structure to store the terminal metadata in. It looks to me from the stub code in glibc that this error represents a null pointer for the termios struct. I am not sure whether these same error handling semantics are in place for the platform-specific implementations of tcgetattr.
If you want to suppress this error, invoke ssh like so:
ssh 2>/dev/null
This will redirect STDERR to /dev/null; you won't see the error when invoking with this redirection. Note that this will mask other errors with ssh; you may need to remove this for debugging purposes.