lessc: 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/lessc - from package: nodejs-less
/usr/lib/node_modules/less/bin/lessc - from package: nodejs-less

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

On Debian possible default full paths are:

/usr/bin/lessc - from package: node-less
/usr/share/openstack-dashboard/bin/less/lessc - from package: openstack-dashboard

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

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