sudo apt install adb

 $ sudo apt install adb
[sudo] password for dhwan:
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  android-libadb android-libbase android-libboringssl
  android-libcrypto-utils android-libcutils android-liblog
  android-sdk-platform-tools-common
The following NEW packages will be installed:
  adb android-libadb android-libbase android-libboringssl
  android-libcrypto-utils android-libcutils android-liblog
  android-sdk-platform-tools-common
0 upgraded, 8 newly installed, 0 to remove and 17 not upgraded.
Need to get 851 kB of archives.
After this operation, 2.680 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 android-liblog amd64 1:8.1.0+r23-5ubuntu2 [41,9 kB]
Get:2 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 android-libbase amd64 1:8.1.0+r23-5ubuntu2 [22,4 kB]
Get:3 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 android-libboringssl amd64 8.1.0+r23-2build1 [538 kB]
Get:4 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 android-libcrypto-utils amd64 1:8.1.0+r23-5ubuntu2 [8.324 B]
Get:5 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 android-libcutils amd64 1:8.1.0+r23-5ubuntu2 [22,5 kB]
Get:6 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 android-libadb amd64 1:8.1.0+r23-5ubuntu2 [123 kB]
Get:7 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 adb amd64 1:8.1.0+r23-5ubuntu2 [87,6 kB]
Get:8 http://id.archive.ubuntu.com/ubuntu focal/universe amd64 android-sdk-platform-tools-common all 27.0.0+12 [6.648 B]
Fetched 851 kB in 4s (219 kB/s)                              
Selecting previously unselected package android-liblog.
(Reading database ... 314975 files and directories currently installed.)
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Unpacking android-liblog (1:8.1.0+r23-5ubuntu2) ...
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eb ...
Unpacking android-libcutils (1:8.1.0+r23-5ubuntu2) ...
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Unpacking android-sdk-platform-tools-common (27.0.0+12) ...
Setting up android-sdk-platform-tools-common (27.0.0+12) ...
Setting up android-liblog (1:8.1.0+r23-5ubuntu2) ...
Setting up android-libboringssl (8.1.0+r23-2build1) ...
Setting up android-libcrypto-utils (1:8.1.0+r23-5ubuntu2) ...
Setting up android-libbase (1:8.1.0+r23-5ubuntu2) ...
Setting up android-libcutils (1:8.1.0+r23-5ubuntu2) ...
Setting up android-libadb (1:8.1.0+r23-5ubuntu2) ...
Setting up adb (1:8.1.0+r23-5ubuntu2) ...
Processing triggers for man-db (2.9.1-1) ...
Processing triggers for libc-bin (2.31-0ubuntu9.2) ...