imgrep: 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/imgrep - from package: im

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

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