check your image cmd using the command docker inspect image_name . The output might be like this:
"Cmd": [
"/bin/bash",
"-c",
"#(nop) ",
"CMD [\"/bin/bash\"]"
],
So use the command docker exec -it container_id /bin/bash. If your cmd output is different like this:
"Cmd": [
"/bin/sh",
"-c",
"#(nop) ",
"CMD [\"/bin/sh\"]"
],
Use /bin/sh instead of /bin/bash in the command above.