Installation time of ROS the sudo rosdep the init instruction given:
ERROR: cannot download default sources list from:
https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list
Website may be down.
Solve (the method followed by the implementation until get:
( 1) there had been before installing a version of the ROS system, follow the prompts to delete an existing file to initialize:
sudo rm /etc/ros/rosdep/sources.list.d/20-default.list
( 2) CA-Certificates problem, not certification, re-install the certificate
sudo apt-get install ca-certificates
( 3) System time synchronization problem, need to synchronize system time
sudo apt-get install ntpdate
sudo ntpdate cn.pool.ntp.org
sudo hwclock --systohc
( 4) ssl certs problem sudo c_rehash /etc/ssl/certs sudo -E rosdep init
( 5) Python-rosdep problem sudo apt-get install python-rosdep
( 6) If still invalid, then directly add the contents of the / etc directory /ros/rosdep/sources.list. d / 20-default.list cd /ros/rosdep/sources.list.d (specific directory depends on your user name) sudo gedit 20-default.list copy https://raw.githubusercontent.com/ros/rosdistro/ master / rosdep / sources.list.d / 20- default.list inside the content in, save, exit, re-run sudo rosdep init.
If the link above does not open, or an error time out, to show that you have a network problem, repeat all the steps above to turn it over a wall.