Mini Shell

# This is a more restricted version of the chronyd service intended for
# minimal NTP/NTS client configurations. The daemon is started without root
# privileges and is allowed to write only to its own runtime, state, and log
# directories. It cannot bind to privileged ports in order to operate as an
# NTP server, or provide monitoring access over IPv4/IPv6. It cannot use
# reference clocks, HW timestamping, RTC tracking, and other features.
[Unit]
Description=NTP client (restricted)
Documentation=man:chronyd(8) man:chrony.conf(5)
After=chronyd.service ntpdate.service sntp.service ntpd.service
Conflicts=chronyd.service ntpd.service systemd-timesyncd.service
ConditionCapability=CAP_SYS_TIME

[Service]
Type=forking
PIDFile=/run/chrony/chronyd.pid
EnvironmentFile=-/etc/sysconfig/chronyd
ExecStart=/usr/sbin/chronyd -U $OPTIONS
SELinuxContext=system_u:system_r:chronyd_restricted_t:s0

User=chrony
LogsDirectory=chrony
LogsDirectoryMode=0750
RuntimeDirectory=chrony
RuntimeDirectoryMode=0750
RuntimeDirectoryPreserve=restart
StateDirectory=chrony
StateDirectoryMode=0750

AmbientCapabilities=CAP_SYS_TIME
CapabilityBoundingSet=CAP_SYS_TIME
DevicePolicy=closed
LockPersonality=yes
MemoryDenyWriteExecute=yes
NoNewPrivileges=yes
PrivateDevices=yes
PrivateTmp=yes
# This breaks adjtimex()
#PrivateUsers=yes
ProtectControlGroups=yes
ProtectHome=yes
ProtectHostname=yes
ProtectKernelLogs=yes
ProtectKernelModules=yes
ProtectKernelTunables=yes
ProtectProc=invisible
ProtectSystem=strict
RemoveIPC=yes
RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX
RestrictNamespaces=yes
RestrictRealtime=yes
RestrictSUIDSGID=yes
SystemCallArchitectures=native
SystemCallFilter=~@cpu-emulation @debug @module @mount @obsolete @raw-io
SystemCallFilter=~@reboot @resources @swap
UMask=0077

[Install]
WantedBy=multi-user.target