unsquashfs: 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/sbin/unsquashfs - from package: squashfs-tools

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

On Debian possible default full paths are:

/usr/bin/unsquashfs - from package: squashfs-tools

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

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