lupdate: 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/lib64/qt-3.3/bin/lupdate - from package: qt3-devel
/usr/lib/qt-3.3/bin/lupdate - from package: qt3-devel
/usr/lib64/qt5/bin/lupdate - from package: qt5-linguist
/usr/lib64/qt4/bin/lupdate - from package: qt-devel
/usr/lib/qt4/bin/lupdate - from package: qt-devel

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

On Debian possible default full paths are:

/usr/lib/x86_64-linux-gnu/qt4/bin/lupdate - from package: qt4-linguist-tools
/usr/share/qt4/bin/lupdate - from package: qt4-linguist-tools
/usr/bin/lupdate - from package: qtchooser
/usr/lib/x86_64-linux-gnu/qt5/bin/lupdate - from package: qttools5-dev-tools

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

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