[ale] chroot and /proc?

[Jerry Yu]

can a regular file  ./proc/cpuinfo  containing the correct info fool  it?
I'd think fopen won't care if the file is on real fs or not.

2008/4/1 Jeff Lightner <jlightner at water.com>:

>   I guess I should have mentioned the OP on the BIND list specifically
> stated that using "-n 4" still only resulted in BIND finding 1 CPU.
>
>
>
> Later discussion on the BIND list (after I'd posted here) indicates:
>
> After quick look into bind and glibc code /proc has to be mounted.
>
> named calls sysconf(3) function and internal glibc implementation looks
> like this:
>
>
>
> __get_nprocs () {
>
> ..
>
>   FILE *fp = fopen ("/proc/stat", "rc");
>
>   if (fp != NULL) {
>
>     ..
>
>   } else {
>
>     fp = fopen ("/proc/cpuinfo", "rc");
>
>     if (fp != NULL) {
>
>       ..
>
>     }
>
>     ..
>
>   }
>
>
>
>   return 1;
>
> }
>
>
>
> So if you don't have /proc mounted in chroot glibc is not able to get
> number of CPUs and returns 1. When you don't need detect correct number of
> CPUs (always use one CPU) then you don't have to mount /proc
>
>
>
> The poster was from RedHat and in a later post indicated he was going to
> work on a patch to determine number of CPUs BEFORE BIND starts the chroot
> environment as suggested in response to the above.
>
>
>
> That seems to sum it up nicely for me.
>
>
>  ------------------------------
>
> *From:* ale-bounces at ale.org [mailto:ale-bounces at ale.org] *On Behalf Of *Jason
> Fritcher
> *Sent:* Tuesday, April 01, 2008 2:20 PM
> *To:* ale at ale.org
> *Subject:* Re: [ale] chroot and /proc?
>
>
>
>
>
> On Apr 1, 2008, at 12:09 PM, Jeff Lightner wrote:
>
>  Alternatively I'm wondering if there isn't a better way to let the chroot
> environment BIND know that there are 4 CPUs?
>
>
>
> Sure, there is a command-line option to tell it how many CPUs there are...
>
>
>
>        -n #cpus
>
>           Create #cpus worker threads to take advantage of multiple CPUs.
> If
>
>           not specified, named will try to determine the number of CPUs
>
>           present and create one thread per CPU. If it is unable to
> determine
>
>           the number of CPUs, a single worker thread will be created.
>
>
>
> --
>
> Jason Fritcher
>
> jkf at wolfnet.org
>
>
>
>
>
>
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