sq: 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/sq - from package: squirrel

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

On Debian possible default full paths are:

/usr/bin/sq - from package: ispell

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

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