printk/kernel/ignore_loglevel

 

loglevel=       All Kernel Messages with a loglevel smaller than the
                    console loglevel will be printed to the console. It can
                    also be changed with klogd or other programs. The
                    loglevels are defined as follows:

                    0 (KERN_EMERG)          system is unusable
                    1 (KERN_ALERT)          action must be taken immediately
                    2 (KERN_CRIT)           critical conditions
                    3 (KERN_ERR)            error conditions
                    4 (KERN_WARNING)        warning conditions
                    5 (KERN_NOTICE)         normal but significant condition
                    6 (KERN_INFO)           informational
                    7 (KERN_DEBUG)          debug-level messages

 

 

1. how to generate kernel messages via /dev/kmsg

 
    echo  "8 4 1 7" >/proc/sys/kernel/print
    
/ #  echo "<7>Writing critical printk messages from userspace" >/dev/kmsg 
    
    Writing critical printk messages from userspace
     
     
/ #  echo "<2>Writing critical printk messages from userspace" >/dev/kmsg
Writing critical printk messages from userspace
/ #  echo "<7>Writing critical printk messages from userspace" >/dev/kmsg
Writing critical printk messages from userspace 

2. loglevel=4 in  cmdline 

CONFIG_MESSAGE_LOGLEVEL_DEFAULT=4  =========> loglevel=4 in  cmdline 

3. ignore_loglevel to ignore setting outside of kernel 

CONFIG_CMDLINE="console=ttyS0,115200 ignore_loglevel    XXXXXXXXXXXX(other default settting of kernel like root=XXXX"
CONFIG_CMDLINE_FORCE=y