boinccmd: 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/boinccmd - from package: boinc-client

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

On Debian possible default full paths are:

/usr/bin/boinccmd - from package: boinc-client

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

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