RMT(8C) RMT(8C) NAME rmt - remote magtape protocol module SYNOPSIS /etc/rmt DESCRIPTION _R_m_t is a program used by the remote dump and restore programs in manip‐ ulating a magnetic tape drive through an interprocess communication connection. _R_m_t is normally started up with an _r_e_x_e_c(3X) or _r_c_m_d(3X) call. The _r_m_t program accepts requests specific to the manipulation of mag‐ netic tapes, performs the commands, then responds with a status indica‐ tion. All responses are in ASCII and in one of two forms. Successful commands have responses of A_n_u_m_b_e_r\n where _n_u_m_b_e_r is an ASCII representation of a decimal number. Unsuc‐ cessful commands are responded to with E_e_r_r_o_r_-_n_u_m_b_e_r\n_e_r_r_o_r_-_m_e_s_s_a_g_e\n, where _e_r_r_o_r_-_n_u_m_b_e_r is one of the possible error numbers described in _i_n_t_r_o(2) and _e_r_r_o_r_-_m_e_s_s_a_g_e is the corresponding error string as printed from a call to _p_e_r_r_o_r(3). The protocol is comprised of the following commands (a space is present between each token). O device mode Open the specified _d_e_v_i_c_e using the indicated _m_o_d_e. _D_e_v_i_c_e is a full pathname and _m_o_d_e is an ASCII represen‐ tation of a decimal number suitable for passing to _o_p_e_n(2). If a device had already been opened, it is closed before a new open is performed. C device Close the currently open device. The _d_e_v_i_c_e specified is ignored. L whence offset Perform an _l_s_e_e_k(2) operation using the specified param‐ eters. The response value is that returned from the _l_s_e_e_k call. W count Write data onto the open device. _R_m_t reads _c_o_u_n_t bytes from the connection, aborting if a premature end-of-file is encountered. The response value is that returned from the _w_r_i_t_e(2) call. R count Read _c_o_u_n_t bytes of data from the open device. If _c_o_u_n_t exceeds the size of the data buffer (10 kilobytes), it is truncated to the data buffer size. _R_m_t then performs the requested _r_e_a_d(2) and responds with A_c_o_u_n_t_-_r_e_a_d\n if the read was successful; otherwise an error in the stan‐ dard format is returned. If the read was successful, the data read is then sent. I operation count Perform a MTIOCOP _i_o_c_t_l(2) command using the specified parameters. The parameters are interpreted as the ASCII representations of the decimal values to place in the _m_t__o_p and _m_t__c_o_u_n_t fields of the structure used in the _i_o_c_t_l call. The return value is the _c_o_u_n_t parameter when the operation is successful. S Return the status of the open device, as obtained with a MTIOCGET _i_o_c_t_l call. If the operation was successful, an ‘‘ack’’ is sent with the size of the status buffer, then the status buffer is sent (in binary). Any other command causes _r_m_t to exit. DIAGNOSTICS All responses are of the form described above. SEE ALSO rcmd(3X), rexec(3X), mtio(4), rdump(8C), rrestore(8C) BUGS People tempted to use this for a remote file access protocol are dis‐ couraged. 4.2 Berkeley Distribution April 27, 1985 RMT(8C)