imhead: 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/imhead - from package: wcstools

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

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