ldd: 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/ldd - from package: glibc-common

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

On Debian possible default full paths are:

/usr/bin/ldd - from package: libc-bin

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

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