In Android, there is a property system that we can manipulate using commands like getprop and setprop, corresponding to files such as /default.prop, /system/build.prop, /system/default.prop, and /data/local.prop. But does a similar system exist in the Linux environment beneath Android? Certainly, it does, and this system is aptly designed for the Kernel, while Android’s system is aimed at applications and the Framework (collectively referred to as the upper layer). This way, the interference between the two layers is minimized unless there are services in between that link them for processing.
So, how does this system work in the Linux Kernel? In the Linux command line, the sysctl command is used to operate it, based on various leaf files in the /proc/sys/ directory. The attributes printed by sysctl -a include the following example:
1. Viewing attribute values
Besides the sysctl -a command that prints all kernel parameters, you can also print the value of a specific parameter:
sysctl net.ipv4.tcp_syncookies2. Setting a specific attribute value
sudo sysctl -w net.ipv4.tcp_syncookies="1"3. Making it permanent
The above setting is only temporary, meaning it modifies the parameters during system operation to change the system’s operational direction for temporary debugging and testing purposes. To make it permanent, you can modify the /etc/sysctl.conf file, which contains the following:
net.ipv4.tcp_syncookies=1Thus, we have briefly covered the settings of runtime parameters in the Linux Kernel. For more detailed usage instructions regarding the sysctl command, you can use man sysctl.