mongoimport: 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/mongoimport - from package: mongodb

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

On Debian possible default full paths are:

/usr/bin/mongoimport - from package: mongodb-clients

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

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