Mini Shell

[Unit]
Description=Wait for chrony to synchronize system clock
Documentation=man:chronyc(1)
After=chronyd.service
Requires=chronyd.service
Before=time-sync.target
Wants=time-sync.target

[Service]
Type=oneshot
# Wait for chronyd to update the clock and the remaining
# correction to be less than 0.1 seconds
ExecStart=/usr/bin/chronyc -h 127.0.0.1,::1 waitsync 0 0.1 0.0 1
# Wait for at most 3 minutes
TimeoutStartSec=180
RemainAfterExit=yes
StandardOutput=null

CapabilityBoundingSet=
DevicePolicy=closed
#DynamicUser=yes
IPAddressAllow=localhost
IPAddressDeny=any
LockPersonality=yes
MemoryDenyWriteExecute=yes
PrivateDevices=yes
PrivateUsers=yes
ProtectClock=yes
ProtectControlGroups=yes
ProtectHome=yes
ProtectHostname=yes
ProtectKernelLogs=yes
ProtectKernelModules=yes
ProtectKernelTunables=yes
ProtectProc=invisible
ProtectSystem=strict
RestrictAddressFamilies=AF_INET AF_INET6
RestrictNamespaces=yes
RestrictRealtime=yes
SystemCallArchitectures=native
SystemCallFilter=@system-service
SystemCallFilter=~@privileged @resources
UMask=0777

[Install]
WantedBy=multi-user.target