palimpsest: 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/palimpsest - from package: gnome-disk-utility

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

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