On 17.1 this does not appear to be an available option even as root.
{master}
root@ex9204-core2-re0> request system ?
Possible completions:
certificate Manage X509 certificates
commit Perform commit related operations
configuration Request operation on system configuration
decrypt Decrypt a $8$ or $9$-encrypted password
license Manage feature licenses
logout Forcibly end user's CLI login session
personality-file Execute commands related to personality of a device
process Request operation on system process
reboot Reboot the system
recover Recover a specified volume
scripts Manage scripts (commit, op, event)
snapshot Create a normal Junos or a recovery snapshot
software Perform system software extension or upgrade
storage Request operation on system storage
yang Perform YANG schema operations
zeroize Erase all data, including configuration and log files
{master}root@ex9204-core2-re0> show version Hostname: ex9204-core2-re0 Model: ex9204 Junos: 17.1R2.7 JUNOS OS Kernel 64-bit [20170607.351421_builder_stable_10] JUNOS OS libs [20170607.351421_builder_stable_10] JUNOS OS runtime [20170607.351421_builder_stable_10] JUNOS OS time zone information [20170607.351421_builder_stable_10] JUNOS network stack and utilities [20170617.054345_builder_junos_171_r2] JUNOS modules [20170617.054345_builder_junos_171_r2] JUNOS mx modules [20170617.054345_builder_junos_171_r2] JUNOS libs [20170617.054345_builder_junos_171_r2] JUNOS OS libs compat32 [20170607.351421_builder_stable_10] JUNOS OS 32-bit compatibility [20170607.351421_builder_stable_10] JUNOS libs compat32 [20170617.054345_builder_junos_171_r2] JUNOS runtime [20170617.054345_builder_junos_171_r2] Junos vmguest package [20170617.054345_builder_junos_171_r2] JUNOS py extensions [20170617.054345_builder_junos_171_r2] JUNOS py base [20170617.054345_builder_junos_171_r2] JUNOS OS vmguest [20170607.351421_builder_stable_10] JUNOS OS crypto [20170607.351421_builder_stable_10] JUNOS Web Management Platform Package [20170617.054345_builder_junos_171_r2] JUNOS mx libs compat32 [20170617.054345_builder_junos_171_r2] JUNOS mx runtime [20170617.054345_builder_junos_171_r2] JUNOS common platform support [20170617.054345_builder_junos_171_r2] JUNOS mx libs [20170617.054345_builder_junos_171_r2] JUNOS mtx Data Plane Crypto Support [20170617.054345_builder_junos_171_r2] JUNOS daemons [20170617.054345_builder_junos_171_r2] JUNOS mx daemons [20170617.054345_builder_junos_171_r2] JUNOS Voice Services Container package [20170617.054345_builder_junos_171_r2] JUNOS Services TLB Service PIC package [20170617.054345_builder_junos_171_r2] JUNOS Services SSL [20170617.054345_builder_junos_171_r2] JUNOS Services Stateful Firewall [20170617.054345_builder_junos_171_r2] JUNOS Services RPM [20170617.054345_builder_junos_171_r2] JUNOS Services PTSP Container package [20170617.054345_builder_junos_171_r2] JUNOS Services PCEF package [20170617.054345_builder_junos_171_r2] JUNOS Services NAT [20170617.054345_builder_junos_171_r2] JUNOS Services Mobile Subscriber Service Container package [20170617.054345_builder_junos_171_r2] JUNOS Services MobileNext Software package [20170617.054345_builder_junos_171_r2] JUNOS Services Logging Report Framework package [20170617.054345_builder_junos_171_r2] JUNOS Services LL-PDF Container package [20170617.054345_builder_junos_171_r2] JUNOS Services Jflow Container package [20170617.054345_builder_junos_171_r2] JUNOS Services Deep Packet Inspection package [20170617.054345_builder_junos_171_r2] JUNOS Services IPSec [20170617.054345_builder_junos_171_r2] JUNOS Services IDS [20170617.054345_builder_junos_171_r2] JUNOS IDP Services [20170617.054345_builder_junos_171_r2] JUNOS Services HTTP Content Management package [20170617.054345_builder_junos_171_r2] JUNOS Services Crypto [20170617.054345_builder_junos_171_r2] JUNOS Services Captive Portal and Content Delivery Container package [20170617.054345_builder_junos_171_r2] JUNOS Services COS [20170617.054345_builder_junos_171_r2] JUNOS Border Gateway Function package [20170617.054345_builder_junos_171_r2] JUNOS AppId Services [20170617.054345_builder_junos_171_r2] JUNOS Services Application Level Gateways [20170617.054345_builder_junos_171_r2] JUNOS Services AACL Container package [20170617.054345_builder_junos_171_r2] JUNOS SDN Software Suite [20170617.054345_builder_junos_171_r2] JUNOS Extension Toolkit [20170617.054345_builder_junos_171_r2] JUNOS jplatform ex92xx [20170617.054345_builder_junos_171_r2] JUNOS Packet Forwarding Engine Support (wrlinux) [20170617.054345_builder_junos_171_r2] JUNOS Packet Forwarding Engine Support (MX/EX92XX Common) [20170617.054345_builder_junos_171_r2] JUNOS Packet Forwarding Engine Support (M/T Common) [20170617.054345_builder_junos_171_r2] JUNOS Packet Forwarding Engine Support (MX Common) [20170617.054345_builder_junos_171_r2] JUNOS jfirmware [20170617.054345_builder_junos_171_r2] JUNOS Online Documentation [20170617.054345_builder_junos_171_r2] JUNOS jail runtime [20170607.351421_builder_stable_10]