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I'm expanding my RAID array (Linux software RAID) and have run into what appears to be a hard limit of 16TB on the XFS file system. Poking around on Google seems to indicate that this is a result of my machine being 32-bit. So I looked up some relevant info on my machine...

## cat /proc/cpuinfo
processor       : 0
vendor_id       : AuthenticAMD
cpu family      : 16
model           : 6
model name      : AMD Sempron(tm) 140 Processor
stepping        : 2
cpu MHz         : 2699.746
cache size      : 1024 KB
fdiv_bug        : no
hlt_bug         : no
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx mmxext fxsr_opt pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc up nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt
bogomips        : 5399.49
clflush size    : 64
cache_alignment : 64
address sizes   : 48 bits physical, 48 bits virtual
power management: ts ttp tm stc 100mhzsteps hwpstate

and...

## uname -a
Linux gibson 2.6.33.4-smp #2 SMP Wed May 12 22:47:36 CDT 2010 i686 AMD Sempron(tm) 140 Processor AuthenticAMD GNU/Linux

I'm far from an expert in Linux system administration or kernel configuration. However, it appears to me that my CPU is 64-bit but it's just the kernel that's keeping things 32-bit. Is that correct? (This question points me to the i686 in the uname output as a clue.)

I found a post online which gives hope that I may just be able to re-compile my kernel with 64-bit support. But I've never actually done that before. (At least, not on a system the functioning of which I consider to be critically important.)

Is this something that can easily be done? Does anybody have a good (and simple) walkthrough of a kernel re-compile (including rollback and recovery tips if the computer fails to use the new kernel) and can maybe point me to the specific make menuconfig options I need to set?

For reference, I'm running Slackware 13.1.0 with Linux 2.6.33.4

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2 Answers 2

up vote 5 down vote accepted

The lm (long mode) flag means your CPU is 64-bit capable. However, you have to change a lot more than just the kernel to have a 64-bit system. I'd strongly suggest backing up everything you care about and reinstalling the 64-bit version of your distribution.

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I'd suggest reinstalling too. I don't think it is worth the trouble. –  sinni800 Nov 11 '11 at 7:49
    
You're probably right. Everything I care about is on the RAID, so it should be easily portable. I'll just have to make sure I keep my mdadm.conf and other such things from the root. This will be an interesting test of that portability. Hopefully I'm not back here in a couple days asking how to recover a RAID... –  David Nov 11 '11 at 11:44
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This might be what you're looking for:

http://alien.slackbook.org/dokuwiki/doku.php?id=linux:kernelbuilding

IIRC, You're going to need to install the 64-bit versions of many of the libraries. I don't know the exact procedure for Slackware, as I haven't used it in years.

As for roll-back/recovery, you can just leave the menu options for the old kernel in GRUB.

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