Useful Command for Troubleshooting - RHEL 6

• Look at the boot time kernel messages:

# less /var/log/dmesg
 

• Look at the latest kernel messages:

# dmesg|tail
 

• Look for any entries in /var/log/messages pertaining to eth0 but exclude any entries containing DHCP:

# grep -i eth0 /var/log/messages*|grep -v DHCP
​

• Look for the rsyslogd process in ps output:

# ps ax |grep rsyslogd
 

• Look for the rsyslogd or init processes in ps output:

​# ps ax | grep -E "rsyslogd|init"
 

• Look at the first line in /etc/passwd:

# head -1 /etc/passwd
 

• Look at the last two lines in /etc/passwd.

# tail -2 /etc/passwd
 

• Show the output of a command, then show it again but remove the first line (header text) only:

# swapon -s # swapon -s|tail -n +2
 

• Get the output of df (-P removes line breaks), remove the header text, and only print the last column which consists of the mounted filesystems:

# df -P | tail -n +2 |awk '{print $6}'
 

• Run the lspci command with extra verbosity:

# lspci -vvv|less