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Partitioning with LVM
by Cen Tos 04 Apr '07

04 Apr '07

I've been reading up on recommended partitioning scheme and looking at Centos 5 beta's default scheme, it struck me that with LVM, it doesn't matter any more as long as we leave aside enough room for /boot, does it? Or am I still missing something here? Thanks!

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Problem with gettid() on CentOS 5/gcc 4.1.1
by Alfred von Campe 04 Apr '07

04 Apr '07

I can't get the simple program below to compile on CentOS 5 beta. It compiles (and runs) just fine on CentOS 4.4, and I'm using gettid() as described in the man page. I wonder if this is a problem with RHEL 5 as well, but I don't have a system to test on. I also wonder if this is a gcc 4.1.1 issue or something missing in CentOS 5. The issue is that the _syscall0 macro is not defined anywhere. If I copy and paste the following definition for _syscall0 from a CentOS 4.4 system into the test program, it works just fine: #define _syscall0(type,name) \ type name(void) \ {\ return syscall(__NR_##name);\ } Has anyone else run into this problem? Alfred #include <stdio.h> #include <sys/types.h> #include <linux/unistd.h> #include <errno.h> _syscall0(pid_t, gettid) int main(int argc, char *argv[]) { printf("My tid is 0x%08x\n", gettid()); }

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command to see if a process is being spread among multiple cpus
by Erick Perez 04 Apr '07

04 Apr '07

What command can I use to check if a specific process is being spreaded among multiple cpus? -- ------------------------------------------------------------ Erick Perez ------------------------------------------------------------

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kernel 2.6.13
by Mark Quitoriano 04 Apr '07

04 Apr '07

Hi, i'm just wodering if all the features and bug fixes of 2.6.13 kernel is in the latest kernel. and which one is the latest? kernel-smp#2.6.9-42.0.8.plus.c4 kernel-smp#2.6.9-42.0.8.EL or they're different kernels?

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CentOS 4.4 32 bits not recognizing disks
by Mário Gamito 04 Apr '07

04 Apr '07

Hi, I have to install this server with an Intel motherboard ASUS, model P5VDC-MX. It has a VIA hardware RAID controller model VT-8251. The two hard drives are SATA (don't know if II) and are Maxtor STM380211AS. Problem is that CentOS installation doesn't recognize any hard drives at all. The BIOS setup doesn't have an option to turn off SATA. Any ideas ? Thanks in advance. -- :wq! Mário Gamito

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Where is the LVM config stored?
by WipeOut 04 Apr '07

04 Apr '07

Hi, I am trying to migrate one of my systems to a VMware virtual machine.. The PC is an IDE drive using LVM and the virtual machine is a SCSI drive using ordinary partitions.. Basically I rsynced the entire filesystem from the physical to the virtual machine and that seemed to work just fine.. I installed grub onto the drive in the virtual machine and its booting fine.. The problem comes when the new system trys to scan for the LVM setup that was on the previous PC.. I thought it would scan the drive, and seen that there are no LVM partitions and move on but it doesn't it has a kernel panic and flashes the cap lock and scroll lock LED's on the keyboard.. Obviously somewhere its being told there should be an LVM partition or its being told to scan hda rather than sda.. I have checked the grub.conf and fstab files and they are all right for the new drive setup.. So where is the LVM config? How do I tell it there are now LVM volumes that need to be accessed? Thanks..

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Dell Perc 4dc
by Jon 04 Apr '07

04 Apr '07

Hello, Is the dell perc 4dc raid card supported by centos 4 and does it work reliably? thanks Jon

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software raid
by Dave 04 Apr '07

04 Apr '07

Hello, I've got a 4.4 box that i'd like to implement software raid on. Does anyone have any experiences with this? Thanks. Dave.

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changing motherboards. kernel panic.
by Erick Perez 04 Apr '07

04 Apr '07

Hi, I just changed the motherboard of a centos 4.4 installation for a new one. this new one has a SIS chipset. Now when i boot from the hard disk i get a kernel panic (unable to find root, no hdd found , etc) I have identified the module I need to load to make centos "see" the disks. Now the question is what do I need to modify in my existing installation, to tell centos to use the new sis module and to *not* use the old intel? Thanks, -- ------------------------------------------------------------ Erick Perez ------------------------------------------------------------

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Page cache flushing algorithm question
by Mark Hull-Richter 04 Apr '07

04 Apr '07

I have been studying this for the last several days, and the one thing that leaps out at me is that the page cache always flushes one page at a time. Always. To some extent, there is justification for this - what has to happen for each page that gets flushed depends in part on what file system is being written to and whether or not there is a function for that file system to handle the pages. However, as far as I can tell, if the mapping data for a page does not exist (mapping->a_ops->writepage == NULL), it is handed to mpage_writepage() for buffer management and i/o submission, whereas almost all of the file systems that do map this function map it to block_write_full_page. These two functions use completely different algorithms for flushing a page from the cache, or at least it sure looks that way. (This figures, because if the file system didn't buffer the pages, the kernel has to do it, whereas if the file system did, the flush is much simpler.) (The only ones that don't use block_write_full_page are reiserfs, which does some interesting things with small files, and the networked file systems, which don't write to a disk file per se.) My question is, is it feasible to tweak these functions so that it becomes possible to flush multiple pages at one time (with one function), or is that too large/complex a change to be worth the effort (which would be considerable)? This might be OT since it is a kernel question, but what the heck.... :-) Thanks. Mark Hull-Richter, Linux Kernel Engineer DATAllegro (www.datallegro.com) 85 Enterprise, Second Floor, Aliso Viejo, CA 92656 949-680-3082 - Office 949-330-7691 - fax

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