Login or Register to Ask a Question and Join Our Community

Sponsored Content
Full Discussion: What exactly does Kernel parameters do ?
Top Forums UNIX for Dummies Questions & Answers What exactly does Kernel parameters do ? Post 302822907 by John K on Tuesday 18th of June 2013 11:01:32 AM
Old 06-18-2013
What exactly does Kernel parameters do ?
Virtual Machine running on VMWare workstation 9.2
os : RHEL 5.8
RAM : 2.5GB
Swap : 2.6gb
CPU : 1 virtual CPU


Surprizingly I couldn't find much from googling on What exactly does Kernel parameters do ?

I was under the impression that kernel parameters just set the limits/maximum for a certain resources in the server.

To install Oracle RDBMS in my Linux VM, i set /etc/sysctl.conf as shown below . I found these settings from google.

Code:
$ cat /etc/sysctl.conf
# Kernel sysctl configuration file for Red Hat Linux
#
# For binary values, 0 is disabled, 1 is enabled.  See sysctl(8) and
# sysctl.conf(5) for more details.

# Controls IP packet forwarding
net.ipv4.ip_forward = 0


net.ipv4.conf.default.rp_filter = 1

# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0


kernel.sysrq = 0

kernel.core_uses_pid = 1

# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1

# Controls the maximum size of a message, in bytes
kernel.msgmnb = 65536

# Controls the default maxmimum size of a mesage queue
kernel.msgmax = 65536

# Controls the maximum shared segment size, in bytes
kernel.shmmax = 68719476736

# Controls the maximum number of shared memory segments, in pages
kernel.shmall = 4294967296

kernel.core_pattern = core.%e.%t

# Oracle Settings
net.ipv4.ip_local_port_range=9000 65500
net.ipv4.tcp_rmem = 4096 262144 26214400
net.ipv4.tcp_wmem = 4096 262144 26214400
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
net.ipv4.tcp_timestamps = 0
vm.pagecache=30
vm.swappiness=100
kernel.shmmni=4096
kernel.sem=268 32000 100 142
fs.file-max=6815744
fs.aio-max-nr=1048576
vm.nr_hugepages=32768
#vm.nr_hugepages=0
vm.drop_caches=0
net.core.rmem_default=262144
net.core.wmem_default=262144
net.core.rmem_max=4194304
net.core.wmem_max=1048576

I restarted the VM after after editing /etc/sysctl.conf like above. But the Linux VM was hanging at startup. It took around 1 hour for the VM to actually come up and it was very slow. So, i reverted /etc/sysctl.conf to the original file.

Why was the VM hanging at startup ?

Has it got anything to do with the kernel.shmmax value? But I am just setting a maximum possible value here. Right ?
 

10 More Discussions You Might Find Interesting

1. HP-UX

Display Kernel Parameters

Good Day Please couls somebody tell me how to display Configurable Kernel parameters from the command line. I am able to do it from SAM,but would like to dump the command line output to a text file so I can email it off to HP. Kind Regards Shawn (1 Reply)
Discussion started by: shawnbishop
1 Replies

2. UNIX for Advanced & Expert Users

Tunable kernel parameters

Hi all, I'm at SCO UNIXWARE 7.1.1, my system's memory is larger than dump device, I have found one kernel tunable parameter at SCO website ie SYSDUMP_SELECTIVE which tells me that if set to 1 system will dump only kernel mapped memory, but I'm not sure how to configure this parameter. As well... (2 Replies)
Discussion started by: tayyabq8
2 Replies

3. HP-UX

kernel parameters

I want to change some kernel parameters in HP-UX11, to do with Oracle upgrade/install. I know this is done using SAM. I am told SAM will not let you enter values outside the allowable range. Could anyone tell me if they have experienced anything different? In Solaris, I would copy the... (2 Replies)
Discussion started by: malcqv
2 Replies

4. HP-UX

Need to look at Kernel parameters

Hello all, Can anyone tell me the command line I can use to look at the following Kernel parameters: nfile maxfile maxfile_lim I'm using the Reflection manager connection to my Unix box so I can't use SAM. (3 Replies)
Discussion started by: impunchdrunk
3 Replies

5. HP-UX

Kernel parameters.

I've been trying to find out the following parameters of our Unix box: ==>OS version ==> patch level and the following kernel parameters =>maxfiles_lim =>maxvgs =>nproc =>msgmni =>ncsize =>nfile Could someone help me how would I find the above(commands)? Thanks, Bhagat (1 Reply)
Discussion started by: bhagat.singh-j
1 Replies

6. HP-UX

Adding new kernel parameters

Hi, I'm new to HP-UX. i'm working on HP-UX 11.31 ia64 for testing our product i could able to change the kernel parameter values and i need to add the following parameters to the parameters list semmap = 258 nfile = 2048 msgseg = 7168 msgssz = 32 maxusers = 60 msgmap = 258 msgmax =... (4 Replies)
Discussion started by: jo09
4 Replies

7. Solaris

Which file is read by kernel to set its default system kernel parameters values?

Hi gurus Could anybody tell me which file is read by kernel to set its default system kernal parameters values in solaris. Here I am not taking about /etc/system file which is used to load kernal modules or to change any default system kernal parameter value Is it /dev/kmem file or something... (1 Reply)
Discussion started by: girish.batra
1 Replies

8. Linux

kernel module parameters

Hi, if I install a module with specific parameter, will this parameters applied next time system boots? for exampe, I want to disable InterruptThrottleRate modprobe e1000e InterruptThrottleRate=0 Is this parameter apllied only for this run, or this module will always use this parameter when... (2 Replies)
Discussion started by: Shedon
2 Replies

9. Solaris

Kernel Parameters

Dear All, I want to check whether all essential kernel parameters are installed in my Solaris 10 System. Is there any way to find it. And also how to tune it. Kindly help. Thanks and Regards Rj (8 Replies)
Discussion started by: jegaraman
8 Replies

10. Solaris

Kernel Parameters

Dear All, I have weblogic Portal Installed in the Server solaris 10. How can i verify whether all the kernel parameters are available for this Software and also another question is How to crosscheck a server ( Solaris 10 Sparc ) whether it has all the required kernel parameters. ... (2 Replies)
Discussion started by: jegaraman
2 Replies

LEARN ABOUT X11R4

chcpu

CHCPU(8)						       System Administration							  CHCPU(8)

NAME

       chcpu - configure CPUs

SYNOPSIS

       chcpu -c|-d|-e|-g cpu-list
       chcpu -p mode
       chcpu -r|-h|-V

DESCRIPTION

       chcpu  can  modify  the state of CPUs.  It can enable or disable CPUs, scan for new CPUs, change the CPU dispatching mode of the underlying
       hypervisor, and request CPUs from the hypervisor (configure) or return CPUs to the hypervisor (deconfigure).

       Some options have a cpu-list argument.  Use this argument to specify a comma-separated list of CPUs.  The list can contain  individual  CPU
       addresses  or ranges of addresses.  For example, 0,5,7,9-11 makes the command applicable to the CPUs with the addresses 0, 5, 7, 9, 10, and
       11.

OPTIONS

       -c, --configure cpu-list
	      Configure the specified CPUs.  Configuring a CPU means that the hypervisor takes a CPU from the CPU pool and assigns it to the  vir-
	      tual hardware on which your kernel runs.

       -d, --disable cpu-list
	      Disable the specified CPUs.  Disabling a CPU means that the kernel sets it offline.

       -e, --enable cpu-list
	      Enable the specified CPUs.  Enabling a CPU means that the kernel sets it online.	A CPU must be configured, see -c, before it can be
	      enabled.

       -g, --deconfigure cpu-list
	      Deconfigure the specified CPUs.  Deconfiguring a CPU means that the hypervisor removes the CPU from the virtual  hardware  on  which
	      the Linux instance runs and returns it to the CPU pool.  A CPU must be offline, see -d, before it can be deconfigured.

       -p, --dispatch mode
	      Set  the	CPU  dispatching mode (polarization).  This option has an effect only if your hardware architecture and hypervisor support
	      CPU polarization.  Available modes are:

		     horizontal  The workload is spread across all available CPUs.
		     vertical	 The workload is concentrated on few CPUs.

       -r, --rescan
	      Trigger a rescan of CPUs.  After a rescan, the Linux kernel recognizes the new CPUs.  Use this option on systems that do	not  auto-
	      matically detect newly attached CPUs.

       -V, --version
	      Display version information and exit.

       -h, --help
	      Display help text and exit.

RETURN CODES

       chcpu has the following return codes:

       0      success

       1      failure

       64     partial success

AUTHOR

       Heiko Carstens <heiko.carstens@de.ibm.com>

COPYRIGHT

       Copyright IBM Corp. 2011

SEE ALSO

       lscpu(1)

AVAILABILITY

       The  chcpu  command  is	part  of the util-linux package and is available from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils
       /util-linux/>.

util-linux							     July 2014								  CHCPU(8)
All times are GMT -4. The time now is 01:37 AM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy