install.sh: 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 Debian possible default full paths are:

/usr/share/gforge/plugins/moinmoin/bin/install.sh - from package: fusionforge-plugin-moinmoin
/usr/share/gforge/plugins/scmbzr/bin/install.sh - from package: fusionforge-plugin-scmbzr
/usr/share/gforge/plugins/scmcvs/bin/install.sh - from package: fusionforge-plugin-scmcvs
/usr/share/gforge/plugins/scmsvn/bin/install.sh - from package: fusionforge-plugin-scmsvn
/usr/share/gforge/plugins/sysauthldap/bin/install.sh - from package: fusionforge-plugin-sysauthldap
/usr/share/doc/libpoet-perl/examples/blog/bin/install.sh - from package: libpoet-perl

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

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