Hi,
how can a specific device driver in CentOS 7 be blacklisted, so that it doesn't load at boot time? We have Infiniband adapters which are not completely supported by CentOS and we want to silence the error messages for the time being.
I tried with the files
/etc/modprobe.d/blacklist /etc/modprobe.d/blacklist.conf
and with entries
mlx5_core mlx5_ib
blacklist mlx5_core blacklist mlx5_ib
install mlx5_core /dev/null install mlx5_ib /dev/null
all found on different websites.
None of these entries helps. mlx5_core and mlx5_ib are still loaded and the system is flooded with error messages.
Cheers frank
On 11/15/2017 10:35 AM, Frank Thommen wrote:
I tried with the files /etc/modprobe.d/blacklist /etc/modprobe.d/blacklist.conf and with entries blacklist mlx5_core blacklist mlx5_ib
The "blacklist" entries prevent a module being loaded by its alias (typically a PCI ID), but not from being loaded if something explicitly loads it by module name. Most likely, those modules are included in your initrd.
I'd suggest using the entries described above, and editing grub.conf to add arguments to the kernel command line: rd.driver.blacklist=mlx5_core rd.driver.blacklist=mlx5_ib ... then rebuilding your initrd using "dracut --force"
On 11/15/2017 07:50 PM, Gordon Messmer wrote:
On 11/15/2017 10:35 AM, Frank Thommen wrote:
I tried with the files /etc/modprobe.d/blacklist /etc/modprobe.d/blacklist.conf and with entries blacklist mlx5_core blacklist mlx5_ib
The "blacklist" entries prevent a module being loaded by its alias (typically a PCI ID), but not from being loaded if something explicitly loads it by module name. Most likely, those modules are included in your initrd.
I'd suggest using the entries described above, and editing grub.conf to add arguments to the kernel command line: rd.driver.blacklist=mlx5_core rd.driver.blacklist=mlx5_ib ... then rebuilding your initrd using "dracut --force"
Thanks for the hint. However as this should only be a temporary measure and needs to be done on ca. 100 hosts I'm not sure if we want to go through the hassles. Deploying a textfile is no problem, but creating new initrds for differing hardware....
frank
On 11/16/2017 08:59 AM, Frank Thommen wrote:
Thanks for the hint. However as this should only be a temporary measure and needs to be done on ca. 100 hosts I'm not sure if we want to go through the hassles. Deploying a textfile is no problem, but creating new initrds for differing hardware....
Well, use "lsinitrd /boot/<initrd>" to confirm that the driver is actually part of yours. If so, I suspect you'll at least need to add the kernel args. At a minimum, that'd require distributing a modified /etc/default/grub and running "grub2-mkconfig -o /etc/grub2-efi.cfg". It might not require any other changes...
Frank Thommen wrote:
** WARNING: This mail is from an external source **
Hi,
how can a specific device driver in CentOS 7 be blacklisted, so that it doesn't load at boot time? We have Infiniband adapters which are not completely supported by CentOS and we want to silence the error messages for the time being.
I tried with the files
/etc/modprobe.d/blacklist /etc/modprobe.d/blacklist.conf
and with entries
mlx5_core mlx5_ib
blacklist mlx5_core blacklist mlx5_ib
install mlx5_core /dev/null install mlx5_ib /dev/null
all found on different websites.
None of these entries helps. mlx5_core and mlx5_ib are still loaded and the system is flooded with error messages.
They are probably being loaded via the initramfs at boot time - i.e. before the real root is mounted (where the blacklist entries exist)
I believe you can either add 'rd.driver.blacklist=<driver_name>' to the grub2 boot cmdline - or generate a new initramfs (using 'dracut -f -v' - make a copy of your current initramfs first) - as this should pull in entries in /etc/modprobe.d/
James Pearson
-----Original Message----- From: James Pearson [mailto:james-p@moving-picture.com] Sent: Friday, November 17, 2017 5:21 AM To: CentOS mailing list; Frank Thommen Subject: Re: [CentOS] How to blacklist a device driver (sysemd)
Frank Thommen wrote:
Hi,
how can a specific device driver in CentOS 7 be blacklisted, so that it doesn't load at boot time? We have Infiniband adapters which are not completely supported by CentOS and we want to silence the error messages for the time being.
I tried with the files
/etc/modprobe.d/blacklist /etc/modprobe.d/blacklist.conf
<SNIP reasonable blacklist changes>
None of these entries helps. mlx5_core and mlx5_ib are still loaded and the system is flooded with error messages.
They are probably being loaded via the initramfs at boot time - i.e. before the real root is mounted (where the blacklist entries exist)
<SNIP> Having had to blacklist things like this in the past, it has been my experience that James is correct. If the driver is available in the existing initrd (created before the updates to the blacklists), then the driver WILL be loaded prior to the blacklists being read. For me I found two solutions that worked: 1) (re)install a new kernel after blacklist creation (which causes an dracut run with all the correct parameters) 2) create the blacklists, then workout the correct dracut parameters and run it.
obviously from the point of avoiding research time, doing a boot into an _older_ kernel, 'yum remove kernel-currentversion; yum update kernel' is easier, but once you figure out how to tell Dracut to use it's usual parameters for each machine you can avoid the time of doing the extra reboot on a bunch of machines. It has been ~4 years since I looked at this so I don't remember how to automate using the right options per machine. Or you could wait for the next CentOS 7 kernel update...Unfortunately the CVE's for the 6 kernel that just came out were all fixed in the 7 kernel back in October, so I have no expectation of a new 7 kernel anytime soon.
-- Even when this disclaimer is not here: I am not a contracting officer. I do not have authority to make or modify the terms of any contract.
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Denniston, Todd A CIV NAVSURFWARCENDIV Crane, JXVS -
Frank Thommen -
Gordon Messmer -
James Pearson