dbclient: 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/dbclient - from package: dropbear

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

On Debian possible default full paths are:

/usr/bin/dbclient - from package: dropbear

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

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