aview: 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 Debian possible default full paths are:

/usr/bin/aview - from package: aview

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

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