Lua mount filesystem

Question

I want to mount a filesystem on Linux using Lua, but I haven't found any capability in the lua 5.4 manual or the LuaFileSytem library. Is there some way to mount a filesystem in Lua or with an existing library?

Answer 1

Like most platform-dependent syscall, Lua won't provide such mapping out of the box. So you'll need some C-API module that does the trick. Looks like https://github.com/justincormack/ljsyscall is generic "but" focused on LuaJIT and https://luaposix.github.io/luaposix/ doesn't provide mount.

I recently had similar needs, and I ended doing the C module:

static int l_mount(lua_State* L)
{
    int res = 0;
    // TODO add more checks on args!
    const char *source = luaL_checkstring(L, 1);
    const char *target = luaL_checkstring(L, 2);
    const char *type   = luaL_checkstring(L, 3);
    lua_Integer flags  = luaL_checkinteger(L, 4);
    const char *data   = luaL_checkstring(L, 5);

    res = mount(source, target, type, flags, data);
    if ( res != 0)
    {
        int err = errno;
        lua_pushnil(L);
        lua_pushfstring(L, "mount failed: errno[%s]", strerror(err));
        return 2;
    }
    else
    {
        lua_pushfstring(L, "ok");
        return 1;
    }
}

#define register_constant(s)\
    lua_pushinteger(L, s);\
    lua_setfield(L, -2, #s);

// Module functions
static const luaL_Reg R[] =
{
    { "mount", l_mount },
    { NULL, NULL }
};

int luaopen_sysutils(lua_State* L)
{
    luaL_newlib(L, R);

    // do more mount defines mapping, maybe in some table.
    register_constant(MS_RDONLY);
    //...
    
    return 1;
}

Compile this as a C Lua module, and don't forget that you need CAP_SYS_ADMIN to call mount syscall.