在使用docker容器時，有時候需要使用一些其他命令，如ifconfig，telnet等，但是會提示錯誤：
bash-5.0# telnet 11.161.35.45 27017 bash: telnet: command not found
這時候需要執行如下命令（apt命令詳細參考 Linux之yum&apt）：
bash-5.0# apt-get update Get:1 http://security.debian.org/debian-security buster/updates InRelease [65.4 kB] Get:2 http://deb.debian.org/debian buster InRelease [121 kB] Get:3 http://deb.debian.org/debian buster-updates InRelease [51.9 kB] Get:4 http://security.debian.org/debian-security buster/updates/main amd64 Packages [291 kB] Get:5 http://deb.debian.org/debian buster/main amd64 Packages [7907 kB] Get:5 http://deb.debian.org/debian buster/main amd64 Packages [7907 kB] Get:6 http://deb.debian.org/debian buster-updates/main amd64 Packages [10.9 kB] Get:4 http://security.debian.org/debian-security buster/updates/main amd64 Packages [291 kB] Fetched 8297 kB in 2min 37s (53.0 kB/s) Reading package lists... Done bash-5.0#
然后安裝telnet命令：
bash-5.0# apt-get install telnet Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: telnet 0 upgraded, 1 newly installed, 0 to remove and 3 not upgraded. Need to get 70.4 kB of archives. After this operation, 167 kB of additional disk space will be used. Get:1 http://deb.debian.org/debian buster/main amd64 telnet amd64 0.17-41.2 [70.4 kB] Fetched 70.4 kB in 0s (345 kB/s) debconf: delaying package configuration, since apt-utils is not installed Selecting previously unselected package telnet. (Reading database ... 12572 files and directories currently installed.) Preparing to unpack .../telnet_0.17-41.2_amd64.deb ... Unpacking telnet (0.17-41.2) ... Setting up telnet (0.17-41.2) ... update-alternatives: using /usr/bin/telnet.netkit to provide /usr/bin/telnet (telnet) in auto mode