请问下如何配置ptp4l做slaveonly模式

要将ptp4l配置为slave-only模式，需要进行以下步骤：

1. 编辑ptp4l的配置文件，通常在/etc/ptp4l.conf或/etc/linuxptp/ptp4l.conf中：

# /etc/ptp4l.conf
# Config file for ptp4l(8)
#
# The following parameters are not mandatory. They are shown here for
# reference only.

# Specify the PTP clock device.
# Note that the default value of clock_device is the first PTP clock
# that is found on the system.
#clock_device=/dev/ptp0

# Specify the network interface to be used for PTP communication.
# Note that the default value of iface is the first Ethernet interface
# that is found on the system.
#iface=eth0

# Specify the PTP domain number.
# Note that the default value of domain is 0.
#domain=0

# Specify the delay mechanism.
# Note that the default value of delay_mechanism is E2E.
#delay_mechanism=P2P

# Specify the unicast destination address and port.
# Note that the default value of unicast_destinations is empty.
#unicast_destinations=192.168.1.10:319

# Specify the network transport protocol.
# Note that the default value of transport is UDPv4.
#transport=UDPv6

# Specify the PTP operating mode.
# Note that the default value of mode is E2E.
mode=slaveonly

# Specify the preferred PTP clock source.
# Note that the default value of preferred is empty.
#preferred=192.168.1.10:319

# Specify the log level.
# Note that the default value of log_level is NORMAL.
#log_level=ALL

2. 设置ptp4l的工作模式为slave-only，修改ptp4l.conf文件中的mode参数为slaveonly：

mode=slaveonly

3. 保存配置文件并重启ptp4l服务：

sudo systemctl restart ptp4l

这样，ptp4l就会以slave-only模式运行，并且只接收来自master的PTP消息，不会发送PTP消息。