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I am going to install oracle database 12c on oracle linux 7.5. In the process, I have to edit following kernel parameters and set values.

fs.aio-max-nr = 1048576 fs.file-max = 6815744 kernel.shmall = 2097152 kernel.shmmax = 536870912 kernel.shmmni = 4096 kernel.sem = 250 32000 100 128 net.ipv4.ip_local_port_range = 9000 65500 net.core.rmem_default = 262144 net.core.rmem_max = 4194304 net.core.wmem_default = 262144 net.core.wmem_max = 1048586

Documentation says I should edit /etc/sysctl.conf file. When I run cat /etc/sysctl.conf to read current contents it displays following message.

# sysctl settings are defined through files in # /usr/lib/sysctl.d/, /run/sysctl.d/, and /etc/sysctl.d/. # # Vendors settings live in /usr/lib/sysctl.d/. # To override a whole file, create a new file with the same in # /etc/sysctl.d/ and put new settings there. To override # only specific settings, add a file with a lexically later # name in /etc/sysctl.d/ and put new settings there. # # For more information, see sysctl.conf(5) and sysctl.d(5)

When I try to edit with root user in vi, it says sysctl.conf is read only. even when I override with '!', changes does not apply and modify the parameters.

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  • after editing sysctl.conf , changes to the runtime kernel parameters will only be applied after running sysctl -p as root/with sudo. Commented Jun 1, 2018 at 18:10
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    wow..it worked @RuiFRibeiro. thanks for the valuable reply. Commented Jun 1, 2018 at 18:18

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Edits to the file /etc/sysctl.conf normally will only affect the system upon reboot unless you run by hand:

sudo sysctl -p

If you want to set a particular kernel variable at run time, do:

sudo sysctl -w kernel.shmmni=4096

If you want to see all the kernel variables, do:

sysctl -a
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