The /proc interface (cont)

You can change configurable characteristics of the kernel at runtime via /proc entries!

 $ ls -l /proc/sys/fs/file-max
 -rw-r--r--    1 root  root    0 Feb 23 09:46 file-max
 $ cat /proc/sys/fs/file-max
 1024
 $ echo 4096 >  /proc/sys/fs/file-max
 $ cat /proc/sys/fs/file-max
 4096

 $ ls -l /proc/sys/net/ipv4/tcp_syncookies
 -rw-r--r--    1 root  root    0 Feb 23 09:46 tcp_syncookies
 $ cat /proc/sys/net/ipv4/tcp_syncookies
 0
 $ echo 1 > /proc/sys/net/ipv4/tcp_syncookies
 $ cat /proc/sys/net/ipv4/tcp_syncookies
 1

See 'man proc' and 'man sysctl' for more examples