indent: 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/indent - from package: indent

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

On Debian possible default full paths are:

/usr/bin/indent - from package: indent

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

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