Monitoring and debugging

# free -m

displays status of RAM in megabytes [man]

# kill -9 process_id

force closure of the process and finish it [man]

# kill -1 process_id

force a process to reload configuration [man]

# last reboot

show history reboot [man]

# lsmod

display kernel loaded [man]

# lsof -p process_id

display a list of files opened by processes [man]

# lsof /home/user1

displays a list of open files in a given path system [man]

# ps -eafw

displays linux tasks [man]

# ps -e -o pid,args --forest

displays linux tasks in a hierarchical mode [man]

# pstree

Shows a tree system processes [man]

# smartctl -A /dev/hda

monitoring reliability of a hard-disk through SMART [man]

# smartctl -i /dev/hda

check if SMART is active on a hard-disk [man]

# strace -c ls >/dev/null

display system calls made and received by a process [man]

# strace -f -e open ls >/dev/null

display library calls [man]

# tail /var/log/dmesg

show events inherent to the process of booting kernel [man]

# tail /var/log/messages

show system events [man]

# top

display linux tasks using most cpu [man]

# watch -n1 'cat /proc/interrupts'

display interrupts in real-time [man]