# ldattach

## NAME



           ldattach - attach a line discipline to a serial line
    


## SYNOPSIS



           **ldattach**[**-1278denoVh**] [**-i** _iflag_] [**-s** _speed_] [**-m** _mtu_] _ldisc device_
    


## DESCRIPTION



           The **ldattach** daemon opens the specified _device_ file (which should
           refer to a serial device) and attaches the line discipline _ldisc_
           to it for processing of the sent and/or received data. It then
           goes into the background keeping the device open so that the line
           discipline stays loaded.
    
           The line discipline _ldisc_ may be specified either by name or by
           number.
    
           In order to detach the line discipline, kill(1) the **ldattach**
           process.
    
           With no arguments, **ldattach** prints usage information.
    


## LINE DISCIPLINES



           Depending on the kernel release, the following line disciplines
           are supported:
    
           **TTY**(**0**)
               The default line discipline, providing transparent operation
               (raw mode) as well as the habitual terminal line editing
               capabilities (cooked mode).
    
           **SLIP**(**1**)
               Serial Line IP (SLIP) protocol processor for transmitting
               TCP/IP packets over serial lines.
    
           **MOUSE**(**2**)
               Device driver for RS232 connected pointing devices (serial
               mice).
    
           **PPP**(**3**)
               Point to Point Protocol (PPP) processor for transmitting
               network packets over serial lines.
    
           **STRIP**(**4**); **AX25**(**5**); **X25**(**6**)
               Line driver for transmitting X.25 packets over asynchronous
               serial lines.
    
           **6PACK**(**7**); **R3964**(**9**)
               Driver for Simatic R3964 module.
    
           **IRDA**(**11**)
               Linux IrDa (infrared data transmission) driver - see
               http://irda.sourceforge.net/
    
           **HDLC**(**13**)
               Synchronous HDLC driver.
    
           **SYNC_PPP**(**14**)
               Synchronous PPP driver.
    
           **HCI**(**15**)
               Bluetooth HCI UART driver.
    
           **GIGASET_M101**(**16**)
               Driver for Siemens Gigaset M101 serial DECT adapter.
    
           **PPS**(**18**)
               Driver for serial line Pulse Per Second (PPS) source.
    
           **GSM0710**(**21**)
               Driver for GSM 07.10 multiplexing protocol modem (CMUX).
    


## OPTIONS



           **-1** , **--onestopbit**
               Set the number of stop bits of the serial line to one.
    
           **-2** , **--twostopbits**
               Set the number of stop bits of the serial line to two.
    
           **-7** , **--sevenbits**
               Set the character size of the serial line to 7 bits.
    
           **-8** , **--eightbits**
               Set the character size of the serial line to 8 bits.
    
           **-d** , **--debug**
               Keep **ldattach** in the foreground so that it can be interrupted
               or debugged, and to print verbose messages about its progress
               to standard error output.
    
           **-e** , **--evenparity**
               Set the parity of the serial line to even.
    
           **-i** , **--iflag** _value_...
               Set the specified bits in the c_iflag word of the serial line.
               The given _value_ may be a number or a symbolic name. If _value_
               is prefixed by a minus sign, the specified bits are cleared
               instead. Several comma-separated values may be given in order
               to set and clear multiple bits.
    
           **-n** , **--noparity**
               Set the parity of the serial line to none.
    
           **-o** , **--oddparity**
               Set the parity of the serial line to odd.
    
           **-s** , **--speed** _value_
               Set the speed (the baud rate) of the serial line to the
               specified _value_.
    
           **-c** , **--intro-command** _string_
               Define an intro command that is sent through the serial line
               before the invocation of **ldattach**. E.g. in conjunction with
               line discipline GSM0710, the command 'AT+CMUX=0\r' is commonly
               suitable to switch the modem into the CMUX mode.
    
           **-p** , **--pause** _value_
               Sleep for _value_ seconds before the invocation of **ldattach**.
               Default is one second.
    
           **-m** , **--mtu** _value_
               Set maximum frame size for GSM0710 CMUX. If not specified,
               traditionally the default of 127 have been set by **ldattach**.
               This differs from 3GPP TS 27.010 default value of 31 bytes, so
               it is recommended to specify
    
           **-h** , **--help**
               Display help text and exit.
    
           **-V** , **--version**
               Display version and exit.
    


## AVAILABILITY



           The **ldattach** command is part of the util-linux package which can
           be downloaded from Linux Kernel Archive
           <https://www.kernel.org/pub/linux/utils/util-linux/>. This page is
           part of the _util-linux_ (a random collection of Linux utilities)
           project. Information about the project can be found at 
           ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
           bug report for this manual page, send it to
           util-linux@vger.kernel.org. This page was obtained from the
           project's upstream Git repository
           ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on
           2025-08-11. (At that time, the date of the most recent commit that
           was found in the repository was 2025-08-05.) If you discover any
           rendering problems in this HTML version of the page, or you
           believe there is a better or more up-to-date source for the page,
           or you have corrections or improvements to the information in this
           COLOPHON (which is _not_ part of the original manual page), send a
           mail to man-pages@man7.org
    
    util-linux 2.42-start-521-ec46  2025-08-09                    _LDATTACH_(8)
    


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