FTP reply code 450 is a temporary failure indicating the requested file operation could not be performed right now. The file may be locked by another process, the filesystem may be temporarily read-only (during a snapshot or backup), or the server may be experiencing a transient condition that prevents access. Unlike 550 (permanent rejection), 450 means the condition may change — the client should retry the operation after a delay. This code can appear in response to RETR, STOR, DELE, RMD, or any other file operation. The response text usually provides more detail about why the file is unavailable.
Another user or process is currently accessing the file with an exclusive lock. This is common with files being actively written, database files, or files being processed by a server-side script. The lock should be released when the other operation completes.
The filesystem containing the file was remounted read-only, typically during a backup snapshot, filesystem check, or maintenance operation. Write operations (STOR, DELE, MKD) will fail until the filesystem is remounted read-write.
The server has temporarily exhausted a resource needed for the file operation — open file descriptors, inode cache, or I/O bandwidth. The condition should resolve as other operations complete.
Wait 30-60 seconds and retry the operation. The temporary condition (file lock, filesystem snapshot, etc.) should resolve on its own.
If you have server access, check for processes holding the file open. On Linux, use lsof or fuser. The lock will be released when the process finishes.
lsof /path/to/file
If only one file returns 450, the issue is specific to that file. Try accessing other files to determine if the problem is file-specific or server-wide.
The file or directory operation failed. The path does not exist, or access is denied.
The server could not establish the data connection needed for the file transfer.
The server encountered an internal error while processing the command. The client should retry later.
The file transfer completed successfully and the data connection is being closed.