$ ifconfig -a
ens33: flags=4098<BROADCAST,MULTICAST>  mtu 1500
    ether 00:**:**:**:**:**  txqueuelen 1000  (Ethernet)
    RX packets 0  bytes 0 (0.0 B)
    RX errors 0  dropped 0  overruns 0  frame 0
    TX packets 0  bytes 0 (0.0 B)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
    inet 127.0.0.1  netmask 255.0.0.0
    inet6 ::1  prefixlen 128  scopeid 0x10<host>
    loop  txqueuelen 1000  (Local Loopback)
    RX packets 1876  bytes 114200 (114.2 KB)
    RX errors 0  dropped 0  overruns 0  frame 0
    TX packets 1876  bytes 114200 (114.2 KB)
    TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

$ ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: ens33: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
link/ether 00:0c:29:f8:f7:47 brd ff:ff:ff:ff:ff:ff

$ ifup ens33
Unknown interface ens33
$ ifup eth0
Unknown interface eth0