cover: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/cover - from package: golang-cover
/usr/bin/cover - from package: perl-Devel-Cover

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/cover - from package: libdevel-cover-perl

You may install the required package with command apt-get install {package}

Error in other languages:
cover: bevel nie gevind nie
cover: comandă negăsită
cover: comando não encontrado
cover: commande introuvable
cover: command not found
cover: käsku ei ole
cover: không tìm thấy lệnh
cover: komanda nerasta
cover: Kommando nicht gefunden.
cover: kommandot finns inte
cover: komut yok
cover: nie znaleziono polecenia
cover: níor aimsíodh an t-ordú
cover: no se encontró la orden
cover: no s'ha trobat l'ordre
cover: opdracht niet gevonden
cover: parancs nem található
cover: perintah tidak ditemukan
cover: príkaz nenájdený
cover: příkaz nenalezen
cover: команда не найдена
cover: командата не е открита
cover: 命令找不到
cover: コマンドが見つかりません