Kernel¶
Disable bios network names¶
Edit /etc/default/grub and add the following to GRUB_CMDLINE_LINUX
net.ifnames=0 biosdevname=0
Run the command update-grub
USB shuts itself down¶
Append
usbcore.autosuspend=-1
to kernel parameters
What is load?¶
With a quad core system a load average of 5 means that all 4 cpus are busy for 100% and processes to fill another cpu are waiting
http://blog.scoutapp.com/articles/2009/07/31/understanding-load-averages
cat /proc/loadavg
field 1-3 = load average of jobs in the run queue (state R) or waiting for disk I/O (state D) averaged over 1, 5, and 15 minutes
field 4 = number of currently runnable kernel scheduling entities (processes, threads) / number of kernel scheduling entities that currently exist on the system
field 5 PID of the process that was most recently created on the system
Hide other users processes¶
Add hidepid=2 to fstab mount options
proc /proc proc nosuid,noexec,nodev,hidepid=2 0 0
Find out which driver is in use¶
network card
ls -al /sys/class/net/eth5/device/driver/module
generic
lspci | grep VGA
02:00.0 VGA compatible controller: Matrox Electronics Systems Ltd. MGA G200e [Pilot] ServerEngines (SEP1) (rev 02)
find /sys | grep driver.*02:00
or more easy
lspci -vv
Use old network device names¶
Start kernel with the parameters
net.ifnames=0 biosdevname=0
Or disable automatic renaming in udev
ln -s /dev/null /etc/udev/rules.d/80-net-setup-link.rules
Or rename devices with udev
cat > /etc/udev/rules.d/99-rename-to-eth0.rules << EOF
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="$(cat /sys/class/net/ens33/address)", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
EOF
Availale parameters for kernel module¶
modinfo <module_name>
Show current kernel boot parameters¶
cat /proc/cmdline
Hotplug CPUs¶
Enable
echo 1 > /sys/devices/system/cpu/cpu<No>/online
Disable
echo 1 > /sys/devices/system/cpu/cpu<No>/online
Reload CPU microcode without reboot¶
echo 1 > /sys/devices/system/cpu/microcode/reload
Check if virtualization is enabled¶
grep vmx /proc/cpuinfo
Check if TPM is available¶
grep smx /proc/cpuinfo
Hide kernel symbols¶
Create /etc/sysctl.d/50-kptr-restrict.conf
kernel.kptr_restrict = 1