about linux processes and cpu usage - lsof, ps, fuser

[sysconfig]

[Important PS command:]

Important PS command:

I use the following ps commands in order to check for performance probelms:

1) Displaying top CPU_consuming processes:

ps aux | head -1; ps aux | sort -rn +2 | head -10

2) Displaying top 10 memory-consuming processes:

ps aux | head -1; ps aux | sort -rn +3 | head

3) Displaying process in order of being penalized:

ps -eakl | head -1; ps -eakl | sort -rn +5

4) Displaying process in order of priority:

ps -eakl | sort -n +6 | head

5) Displaying process in order of nice value

ps -eakl | sort -n +7

6) Displaying the process in order of time

ps vx | head -1;ps vx | grep -v PID | sort -rn +3 | head -10

7) Displaying the process in order of real memory use

ps vx | head -1; ps vx | grep -v PID | sort -rn +6 | head -10

8) Displaying the process in order of I/O

ps vx | head -1; ps vx | grep -v PID | sort -rn +4 | head -10

9) Displaying WLM classes

ps -a -o pid, user, class, pcpu, pmem, args

10) Determinimg process ID of wait processes:

ps vg | head -1; ps vg | grep -w wait

11) Wait process bound to CPU

ps -mo THREAD -p <PID>


lsof:

       To list all open files, use:
      
             # lsof

       To list all open Internet, x.25 (HP-UX), and UNIX domain files, use:

        # lsof -i -U

       To list all open IPv4 network files in use by the process whose PID is 1234, use:

             # lsof -i 4 -a -p 1234

       To list all files using any protocol on ports 513, 514, or 515 of host wonderland.cc.purdue.edu, use:

             # lsof -i @wonderland.cc.purdue.edu:513-515

       To list all files using any protocol on any port of mace.cc.purdue.edu (cc.purdue.edu is the default domain), use:

             # lsof -i @mace

       To list all open files for login name ââabeââ, or user ID 1234, or process 456, or process 123, or process 789, use:

             # lsof -p 456,123,789 -u 1234,abe

       To list all open files on device /dev/hd4, use:

             # lsof /dev/hd4


     To find the process that has /u/abe/foo open, use:

             # lsof /u/abe/foo

       To send a SIGHUP to the processes that have /u/abe/bar open, use:

             # kill -HUP âlsof -t /u/abe/barâ

       To find any open file, including an open UNIX domain socket file, with the name /dev/log, use:

             # lsof /dev/log

       To find processes with open files on the NFS file system named /nfs/mount/point whose server  is  inaccessible,  and presuming your mount table supplies the device number for /nfs/mount/point, use:

             # lsof -b /nfs/mount/point

       To do the preceding search with warning messages suppressed, use:

             # lsof -bw /nfs/mount/point

       To ignore the device cache file, use:

             # lsof -Di

       To  obtain  PID  and command name field output for each process, file descriptor, file device number, and file inode number for each file of each process, use:

             # lsof -FpcfDi

       To list the files at descriptors 1 and 3 of every process running the lsof command for login  ID  ââabeââ  every  10  seconds, use:

             # lsof -c lsof -a -d 1 -d 3 -u abe -r10

       To list the current working directory of processes running a command that is exactly four characters long and has an  âoâ or âOâ in character three, use this regular expression form of the -c c option:

             # lsof -c /^..o.$/i -a -d cwd

       To find an IP version 4 socket file by its associated numeric dot-form address, use:

             # lsof -i@128.210.15.17   

fuser:

      # fuser -km /home

kills all processes accessing the file system /home in any way.

      # if fuser -s /dev/ttyS1; then :; else something; fi

invokes something if no other process is using /dev/ttyS1.

      # fuser telnet/tcp shows all processes at the (local) TELNET port.

thanx

[Some Important Command to find DDOC Attack]

Some Important Command to find DDOC Attack

netstat -anp |grep 'tcp\|udp' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n

netstat -ntu | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr

netstat -ntu | grep -v TIME_WAIT | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -nr

netstat -an | grep :80 | awk '{print $5}' | cut -f1 -d":" | sort | uniq -c | sort -n

Thanks

netstat Command Example

# netstat –listen

Display open ports and established TCP connections:

# netstat -vatn

For UDP port try following command:

# netstat -vaun

If you want to see FQDN then remove -n flag:

# netstat -vat

lsof Command Examples

Display list of open ports

# lsof -i

To display all open files, use:

# lsof

To display all open IPv4 network files in use by the process whose PID is 9255, use:

# lsof -i 4 -a -p 9255

thnkx

[mits]

list information about TCP sessions on your server (specifically SSH in this example)
# lsof -i tcp@`hostname`:22

COMMAND  PID USER   FD   TYPE DEVICE SIZE NODE NAME
sshd2   7585 root    5u  IPv4  16105       TCP localbox:ssh->your.src.ip.here:5897 (ESTABLISHED)
sshd2   7653 root    5u  IPv4  16188       TCP localbox:ssh->your.src.ip.here:2262 (ESTABLISHED)

list information about all TCP session
# lsof -i tcp@`hostname`

list information about all sockets using port 53 (will display named information on UDP/TCP)
# lsof -i @`hostname`:53

list information about all UDP sessions
# lsof -i udp@`hostname`

will list all open files with "ssh" in them
# lsof -c ssh

list everything but with UIDs insted of the UID name from /etc/passwd
# lsof -l

list all open files with "ssh" and only the UIDs
# lsof -l -c ssh

list all open files for the /tmp dir (very slow), but good for finding that nasty process that's holding a file open (although:  fuser -m /tmp, will do the same thing)
# lsof +D /tmp