If a Red Hat or other Linux host has a conflict with an IP address, is there a way to have it display a warning message on the console or in a log, like Windows and MacOS do?
i.e. my computer has an IP address configured (or received from a DHCP server) but finds another device on the network using the assigned address. Will it log the conflict?
Is there a way to change an i386 RHEL4 machine to run an amd64 kernel, but ensure that it still builds software into same i386 binaries?
On Debian this seems quite straightforward: just install an amd64 kernel (worst case, build one like this guy:
http://www.debian-administration.org/users/jonesy/weblog/1) and prefix everything with "linux32". Then everything that considers uname -m will be unchanged, I just need to handle the few cases that consider uname -r.
What is the Red Hat equivalent? Is the only way a full 64-bit installation on another disk and then chrooting back to the 32-bit system before anyone builds anything? (Even the best examples of that seem to be Debian-based.)
Background: We make a large system that runs on (a variant of) i386 RHEL4. However, some of the larger RHEL build machines now have enough RAM that they might benefit from going 64-bit (for the kernel and maybe some of the bigger build steps). Our build system doesn't support cross-compilation.
We have a couple of servers with 20-30 GB RAM that are running (a variant of) RHEL4. They are currently running the SMP i386 kernel, not x64, not even the hugemem kernel. This means LowMem is confined to < 1G, and thus dentry_cache and ext3_inode_cache to 100M or so each. How can I tell if this is a problem?
Here's a typical vmstat report while it's compiling some Java:
$ vmstat 10
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
1 1 0 19493816 394740 922420 0 0 1058 2292 1491 1020 6 3 80 12
2 1 0 19519480 395244 850156 0 0 1179 1412 1329 1195 9 4 75 12
1 1 0 19557368 392616 828344 0 0 1783 1680 1498 1756 14 5 72 9
I don't like the way bi is nonzero when there is so much memory free. I imagine slabtop could point more directly to the problem but I don't really understand how to interpret its output.
Update: The obvious question is "why not move to x64", Google even has many hits on "64 bit kernel 32 bit userland". But the primary purpose of these machines is to build 32 bit software and I don't know how to guarantee that won't be affected by switching kernels.
i386 Linux kernels can be configured for a 2, 3 or 4 GiB limit on virtual address space per process, AFAIK. Is there something I can query in /proc or elsewhere to tell how the currently-running kernel was configured?
Update: Thanks for the answers on how to query for 4G. Any way I can query for 2G vs 3G?