Bug 754723

Summary: kernel log ring too small
Product: [Fedora] Fedora Reporter: Mads Kiilerich <mads>
Component: kernelAssignee: Kernel Maintainer List <kernel-maint>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 16CC: gansalmon, itamar, jonathan, kernel-maint, madhu.chinakonda
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Fixed In Version: Doc Type: Bug Fix
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Last Closed: 2011-11-17 17:18:23 UTC Type: ---
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Description Mads Kiilerich 2011-11-17 14:56:24 UTC
The kernel log ring is often too small. It will for example be truncated if running "dmesg" after booting a f16 live cd. The increased logging due to systemd might have pushed it over the limit. That makes the dmesg output less useful.

It is possible to increase the buffer size with a kernel boot parameter like log_buf_len=1M , but the default buffer size for Fedora kernels should be something suitable for Fedora systems. It seems like the current default is 64 kB. I suggest making it 128 kB.

Comment 1 Dave Jones 2011-11-17 17:18:23 UTC
it's already set to 128KB. 

If you need it to be bigger, use the boot parameter, as it just wastes memory for those who don't need it to be bigger.

Comment 2 Mads Kiilerich 2011-11-17 17:32:04 UTC
It is not me that need a bigger buffer. It is for example the standard Fedora live image that needs a bigger buffer.

Comment 3 Josh Boyer 2011-11-17 18:20:12 UTC
(In reply to comment #2)
> It is not me that need a bigger buffer. It is for example the standard Fedora
> live image that needs a bigger buffer.

Then you might want to open a bug against spins-kickstarts and suggest they add log_buf_len=<whatever> to the kernel command line.

Comment 4 Dave Jones 2011-11-18 02:42:44 UTC
or just read /var/log/messages instead.
Regardless of how big we make the ring buffer, eventually it's going to wrap around.