Here output of strace command ``` / # strace hostname -f execve("/bin/hostname", ["hostname", "-f"], 0x7ffd0fb7df78 /* 84 vars */) = 0 arch_prctl(ARCH_SET_FS, 0x7f36d29e7d48) = 0 set_tid_address(0x7f36d29e831c) = 34 mprotect(0x7f36d29e4000, 4096, PROT_READ) = 0 mprotect(0x564ae99b0000, 16384, PROT_READ) = 0 getuid() = 0 uname({sysname="Linux", nodename="test-st-0", ...}) = 0 open("/etc/hosts", O_RDONLY|O_CLOEXEC) = 3 fcntl(3, F_SETFD, FD_CLOEXEC) = 0 read(3, "# Kubernetes-managed hosts file."..., 1024) = 248 read(3, "", 1024) = 0 close(3) = 0 open("/etc/hosts", O_RDONLY|O_CLOEXEC) = 3 fcntl(3, F_SETFD, FD_CLOEXEC) = 0 read(3, "# Kubernetes-managed hosts file."..., 1024) = 248 read(3, "", 1024) = 0 close(3) = 0 ioctl(1, TIOCGWINSZ, {ws_row=41, ws_col=173, ws_xpixel=0, ws_ypixel=0}) = 0 writev(1, [{iov_base="test-st-0.test-st.ippbx.svc.clus"..., iov_len=41}, {iov_base="\n", iov_len=1}], 2test-st-0.test-st.ippbx.svc.cluster.local ) = 42 exit_group(0) = ? +++ exited with 0 +++ ``` Looks as `hostname -f` take value from `/etc/hosts` file ``` / # cat /etc/hosts # Kubernetes-managed hosts file. 127.0.0.1 localhost ::1 localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet fe00::0 ip6-mcastprefix fe00::1 ip6-allnodes fe00::2 ip6-allrouters 172.21.0.141 test-st-0.test-st.ippbx.svc.cluster.local test-st-0 ``` Test made using this statefulset. ```yaml apiVersion: apps/v1 kind: StatefulSet metadata: name: test-st spec: podManagementPolicy: Parallel serviceName: test-st replicas: 1 selector: matchLabels: app: test-st template: metadata: labels: app: test-st spec: containers: - name: proxy securityContext: privileged: true image: kamailio/kamailio-ci:master-alpine.debug imagePullPolicy: IfNotPresent command: - /bin/sh args: - "-c" - "sleep 360000000000" ```