Compressing troubleshooting logs

1. Access the device throught managment IP address or console.
2.  user@host> file archive compress source /var/log/* destination /var/tmp/re0.tgz
3. Confirm that the compress archive file has been created.
4. user@host> file list /var/tmp
5. Copy files directly from the master Routing Engine to any local host using FTP, SCP , JWEB or mounted usb.

https://www.juniper.net/documentation/en_US/junos/topics/task/troubleshooting/troubleshooting-logs-compressing.html