root@small-apps9-back:/opt/apps9# apt install tcpdump
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-4.9.0-8-amd64 linux-headers-4.9.0-8-common
Use 'apt autoremove' to remove them.
The following additional packages will be installed:
  libpcap0.8
The following NEW packages will be installed:
  libpcap0.8 tcpdump
0 upgraded, 2 newly installed, 0 to remove and 30 not upgraded.
Need to get 530 kB of archives.
After this operation, 1448 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://deb.debian.org/debian stretch/main amd64 libpcap0.8 amd64 1.8.1-3 [138 kB]
Get:2 http://security.debian.org/debian-security stretch/updates/main amd64 tcpdump amd64 4.9.3-1~deb9u1 [391 kB]
Fetched 530 kB in 0s (1582 kB/s)
apt-listchanges: Can't set locale; make sure $LC_* and $LANG are correct!
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
	LANGUAGE = "en_US:en",
	LC_ALL = (unset),
	LC_TIME = "ru_RU.UTF-8",
	LC_MONETARY = "ru_RU.UTF-8",
	LC_ADDRESS = "ru_RU.UTF-8",
	LC_TELEPHONE = "ru_RU.UTF-8",
	LC_NAME = "ru_RU.UTF-8",
	LC_MEASUREMENT = "ru_RU.UTF-8",
	LC_IDENTIFICATION = "ru_RU.UTF-8",
	LC_NUMERIC = "ru_RU.UTF-8",
	LC_PAPER = "ru_RU.UTF-8",
	LANG = "en_US.UTF-8"
    are supported and installed on your system.
perl: warning: Falling back to a fallback locale ("en_US.UTF-8").
locale: Cannot set LC_ALL to default locale: No such file or directory
Selecting previously unselected package libpcap0.8:amd64.
(Reading database ... 70178 files and directories currently installed.)
Preparing to unpack .../libpcap0.8_1.8.1-3_amd64.deb ...
Unpacking libpcap0.8:amd64 (1.8.1-3) ...
Selecting previously unselected package tcpdump.
Preparing to unpack .../tcpdump_4.9.3-1~deb9u1_amd64.deb ...
Unpacking tcpdump (4.9.3-1~deb9u1) ...
Processing triggers for libc-bin (2.24-11+deb9u4) ...
Processing triggers for man-db (2.7.6.1-2) ...
Setting up libpcap0.8:amd64 (1.8.1-3) ...
Setting up tcpdump (4.9.3-1~deb9u1) ...
Processing triggers for libc-bin (2.24-11+deb9u4) ...