Linux Monitoring Tools

Need to monitor Linux server performance? Try these built-in command and a few add-on tools. Most Linux distributions are equipped with tons of monitoring. These tools provide metrics which can be used to get information about system activities. You can use these tools to find the possible causes of a performance problem. The commands discussed below are some of the most basic commands when it comes to system analysis and debugging server

Monitoring the system:

pstree	Processes and parent-child relationships
top	Show top processes
iostat	Report CPU statistics and input/output statistics for devices and partitions.
ps -auxw	process status
uname -a	print system information
cat /proc/version	Display Linux kernel version in use.
cat /etc/redhat-release	Display Red Hat Linux Release. (also /etc/issue)
uptime	Tell how long the system has been running. Also number of users and system's load average.
w	Show who is logged on and what they are doing.
/sbin/lsmod	List all currently loaded kernel modules. Same as cat /proc/modules
/sbin/runlevel	Displays the system's current runlevel.
hostname	Displays/changes the system's node name. (Must also manually change hostname setting in /etc/sysconfig/network. Command will change entry in /etc/hosts)
service	Red Hat/Fedora command to display status of system services. Example: service --status-all Help: service --help

Process Management:

• pstree -p
  OR
• ps -auxw
  OR
• top
• kill <process-id-number>
• killall <command-name>

Memory Usage:

vmstat	Monitor virtual memory
free	Display amount of free and used memory in the system. (Also: cat /proc/meminfo)
pamp	Display/examine memory map and libraries (so). Usage: pmap pid
top	Show top processes
sar -B	Show statistics on page swapping.
time -v date	Show system page size, page faults, etc of a process during execution. Note you must fully qualify the command as "/usr/bin/time" to avoid using the bash shell command "time".
cat /proc/sys/vm/freepages	Display virtual memory "free pages". One may increase/decrease this limit: echo 300 400 500 > /proc/sys/vm/freepages
cat /proc/meminfo	Show memory size and usage.

 

  Filesystems and Storage Devices:

df -k	report filesystem disk space usage. (-k reports in Kbytes)
du -sh	Calculates file space usage for a given directory. (and everything under it) (-s option summarizes)
mount	Displays all mounted devices, their mount point, filesystem, and access. Used with command line arguments to mount file system.
cat /proc/filesystems	Display filesystems currently in use.
cat /proc/mounts	Display mounted filesystems currently in use.
showmount	Displays mount info for NFS filesystems.
cat /proc/swaps	Displays swap partition(s) size, type and quantity used.
cat /proc/ide/hda/any-file	Displays disk information held by kernel.

• cfdisk - Curses based disk partition table manipulator. (very nice)
• fdisk- Manipulate/configure the partition table.
• sfdisk - Manipulate/configure the partition table.
• fsck - Manipulate/configure the partition table. 

User Info:

who	Displays currently logged in users. Use who -uH for idle time and terminal info.
w	Displays currently logged in users and processes they are running.
whoami	Displays user id.
groups	Display groups you are part of. Use groups user-id to display groups for a given user.
set	Display all environment variables in your current environment.
id	Display user and all group ids. Use id user-id to display info for another user id.
last	Listing of most recent logins by users. Show where from, date and time of login (ftp, ssh, ...) Also see lastlog command. Show last 100 logins: last -100
history	Shell command to display previously entered commands.