Linux Commands

Linux Commands

Unset color in vi	: syntax off
	: syntax on
Remove color in ls -lrt	unalias ls
	last |grep boot
To get Ports in use	netstat -a
Solaris mem / cpu	/usr/ucb:./ps auxwww | less
	prstat -a
get CPU usages -	ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10
	sar 1 10
	use sar command
Check Checksum -	cksum ora_DB_nnnnnh54_1_1_796640420_19191_1
run command with Oracle ID	suexec -u oracle /usr/bin/crontab -l
Split with Bytes	split -b 40k myfile segment
Split with Lines	split -l 500 myfile segment

$ /usr/sbin/prtconf |grep -i "Memory size" 

$ swap -s 

$ df -k 

$ /usr/local/bin/top 

$ vmstat 5 100 

$ sar -u 2 100 

$ iostat -D 2 100

$ iostat -x 1 

$ dstat -tdD total, sda, sdb, sdc, md1 60 ( t- timestamp, d - disk stats, -D - exact device to report, 60 - Average over 60 sec in a new line to be started, -c Wait IO Percentage)

$ mpstat 5 100

$ top -n 1 -U oracle -c

$ cat /etc/redhat\-release

To get Make and model of the Linux machine - dmidecode -t system

$ To findout process using the file system -

lsof /backup

alias oenv='echo $ORACLE_SID $TNS_ADMIN $ORACLE_HOME $NLS_ADMIN'

alias pmon='ps -ef|grep pmon|grep $1'

$ stty columns 120 --- On Solaris in case of issues like - Terminal too Wide...

find /dbms/rdbms/audit/ -mtime +1 -type f -exec rm -rf {} \; # to find and remove one plus days old files.

using ipcs -a we can see that the shared memory size is 1055MB.. and using sysdev see that the max shared memory size is 1152MB

Shared Memory:

m 2 0x41545227 --rw-rw-rw- root root root root 0 1048576 2712 3435 15:23:14 15:23:18 15:21:58

m 1003 0xf295b0e4 --rw-r----- oracle dba oracle dba 372 1107099648 25014 28441 15:40:52 15:40:52 15:39:31

*

• IPC Shared Memory

1207959552 max shared memory segment size (SHMMAX)

1 min shared memory segment size (SHMMIN)

125 shared memory identifiers (SHMMNI)

325 max attached shm segments per process (SHMSEG)

iostat 

- reports terminal and disk I/O activity and CPU utilization. The first line of output is for the time period since boot & each subsequent line is for the prior interval . Kernel maintains a number of counters to keep track of the values.

iostat’s activity class options default to tdc (terminal, disk, and CPU). If any other option/s are specified, this default is completely overridden i.e. iostat -d will report only statistics about the disks.

Basic synctax is iostat <options> interval count

option – let you specify the device for which information is needed like disk , cpu or terminal. (-d , -c , -t or -tdc ) . x options gives the extended statistics .

interval - is time period in seconds between two samples . iostat 4 will give data at each 4 seconds interval.

count – is the number of times the data is needed . iostat 4 5 will give data at 4 seconds interval 5 times

$ iostat -xtc 5 2 extended disk statistics tty cpu disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b tin tout us sy wt id sd0 2.6 3.0 20.7 22.7 0.1 0.2 59.2 6 19 0 84 3 85 11 0 sd1 4.2 1.0 33.5 8.0 0.0 0.2 47.2 2 23 sd2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 sd3 10.2 1.6 51.4 12.8 0.1 0.3 31.2 3 31 The fields have the following meanings: disk name of the disk r/s reads per second w/s writes per second Kr/s kilobytes read per second Kw/s kilobytes written per second wait average number of transactions waiting for service (Q length) actv average number of transactions actively being serviced (removed from the queue but not yet completed) %w percent of time there are transactions waiting for service (queue non-empty) %b percent of time the disk is busy (transactions in progress)

Results and Solutions:The values to look from the iostat output are:

Reads/writes per second (r/s , w/s)

Percentage busy (%b) 

Service time (svc_t) 

If a disk shows consistently high reads/writes along with , the percentage busy (%b) of the disks is greater than 5 percent, and the average service time (svc_t) is greater than 30 milliseconds, then one of the following action needs to be taken

1.)Tune the application to use disk i/o more efficiently by modifying the disk queries and using available cache facilities of application servers .

2.) Spread the file system of the disk on to two or more disk using disk striping feature of volume manager /disksuite etc.

3.) Increase the system parameter values for inode cache , ufs_ninode , which is Number of inodes to be held in memory. Inodes are cached globally (for UFS), not on a per-file system basis 

4.) Move the file system to another faster disk /controller or replace existing disk/controller to a faster one.

vmstat - vmstat reports virtual memory statistics of process, virtual memory, disk, trap, and CPU activity.

On multicpu systems , vmstat averages the number of CPUs into the output. For per-process statistics .Without options, vmstat displays a one-line summary of the virtual memory activity since the system was booted.

Basic synctax is vmstat <options> interval count

option – let you specify the type of information needed such as paging -p , cache -c ,.interrupt -i etc.

if no option is specified information about process , memory , paging , disk ,interrupts & cpu is displayed .

interval – is time period in seconds between two samples . vmstat 4 will give data at each 4 seconds interval.

count – is the number of times the data is needed . vmstat 4 5 will give data at 4 seconds interval 5

times.

The following command displays a summary of what the system is doing every five seconds.

example% vmstat 5

procs memory page disk faults cpu r b w swap free re mf pi p fr de sr s0 s1 s2 s3 in sy cs us sy id 0 0 0 11456 4120 1 41 19 1 3 0 2 0 4 0 0 48 112 130 4 14 82 0 0 1 10132 4280 0 4 44 0 0 0 0 0 23 0 0 211 230 144 3 35 62 0 0 1 10132 4616 0 0 20 0 0 0 0 0 19 0 0 150 172 146 3 33 64 0 0 1 10132 5292 0 0 9 0 0 0 0 0 21 0 0 165 105 130 1 21 78

The fields of vmstat’s display are

procs 

r in run queue

b blocked for resources I/O, paging etc.

w swapped

memory (in Kbytes)

swap - amount of swap space currently available 

free – size of the free list

page ( in units per second).

re page reclaims - see -S option for how this field is modified.

mf minor faults - see -S option for how this field is modified.

pi kilobytes paged in

po kilobytes paged out

fr kilobytes freed

de anticipated short-term memory shortfall (Kbytes)

sr pages scanned by clock algorithm

disk ( operations per second )

There are slots for up to four disks, labeled with a single letter and number. 

The letter indicates the type of disk (s = SCSI, i = IPI, etc) . The number is 

the logical unit number.

faults

in (non clock) device interrupts

sy system calls

cs CPU context switches

cpu - breakdown of percentage usage of CPU time. On multiprocessors this is an a

verage across all processors.

us user time

sy system time

id idle time

Results and Solutions:

A. CPU issues:

Following columns has to be watched to determine if there is any cpu issue

Processes in the run queue (procs r) 

User time (cpu us) 

System time (cpu sy) 

Idle time (cpu id)

procs cpu r b w us sy id 0 0 0 4 14 82 0 0 1 3 35 62 0 0 1 3 33 64 0 0 1 1 21 78

Problem symptoms:

1.) If the number of processes in run queue (procs r) are consistently greater than the number of CPUs on the system it will slow down system as there are more processes then available CPUs . 

2.) if this number is more than four times the number of available CPUs in the system then system is facing shortage of cpu power and will greatly slow down the processess on the system.

3.) If the idle time (cpu id) is consistently 0 and if the system time (cpu sy) is double the user time (cpu us) system is facing shortage of CPU resources.

Resolution :

Resolution to these kind of issues involves tuning of application procedures to make efficient use of cpu and as a last resort increasing the cpu power or adding more cpu to the system. 

B. Memory Issues:

Memory bottlenecks are determined by the scan rate (sr) . The scan rate is the pages scanned by the clock algorithm per second. If the scan rate (sr) is continuously over 200 pages per second then there is a memory shortage. 

Resolution :

1. Tune the applications & servers to make efficient use of memory and cache.

2. Increase system memory .

3. Implement priority paging in s in pre solaris 8 versions by adding line “set priority paging=1″ in 

/etc/system. Remove this line if upgrading from Solaris 7 to 8 & retaining old /etc/system file.

netstat displays the contents of various network-related data structures in depending on the options selected.

netstat <option/s>

multiple options can be given at one time.

Options

-a – displays the state of all sockets.

-r – shows the system routing tables

-i – gives statistics on a per-interface basis.

-m – displays information from the network memory buffers. On Solaris, this shows statistics

forSTREAMS

-p [proto] – retrieves statistics for the specified protocol

-s – shows per-protocol statistics. (some implementations allow -ss to remove fileds with a value of 0 (zero) from the display.)

-D – display the status of DHCP configured interfaces.

-n do not lookup hostnames, display only IP addresses.

-d (with -i) displays dropped packets per interface.

-I [interface] retrieve information about only the specified interface.

-v be verbose

$ netstat -rn netstat -rn Routing Table: IPv4 Destination Gateway Flags Ref Use Interface ——————– ——————– —– —– —— ——— 192.168.1.0 192.168.1.11 U 1 1444 le0 224.0.0.0 192.168.1.11 U 1 0 le0 default 192.168.1.1 UG 1 68276  127.0.0.1 127.0.0.1 UH 1 10497 lo0

This shows the output on a Solaris machine who’s IP address is 192.168.1.11 with a default router at 192.168.1.1

Results and Solutions:

A.) Network availability

The command as above is mostly useful in troubleshooting network accessibility issues . When outside network is not accessible from a machine check the following

1. if the default router ip address is correct

2. you can ping it from your machine.

3. If router address is incorrect it can be changed with route add commnad . See man route for more info .

route command examples:

$route add default <hostname>

$route add 192.0.2.32 <gateway_name>

If the router address is correct but still you can’t ping it there may be some network cable /hub/switch problem and you have to try and eliminate the faulty component .

B.) Network Response

$ netstat -i

Name Mtu Net/Dest Address Ipkts Ierrs Opkts Oerrs Collis Queue

lo0 8232 loopback localhost 77814 0 77814 0 0 0

hme0 1500 server1 server1 10658566 3 4832511 0 279257 0

This option is used to diagnose the network problems when the connectivity is there but it is slow in response .

Values to look at:

* Collisions (Collis)

* Output packets (Opkts)

* Input errors (Ierrs)

* Input packets (Ipkts)

The above values will give information to workout

i. Network collision rate as follows :

Network collision rate = Output collision counts / Output packets

Network-wide collision rate greater than 10 percent will indicate

* Overloaded network,

* Poorly configured network,

* Hardware problems. 

ii. Input packet error rate as follows :

Input Packet Error Rate = Ierrs / Ipkts.

If the input error rate is high (over 0.25 percent), the host is dropping packets. Hub/switch cables etc needs to be checked for potential problems.

C. Network socket & TCP Cconnection state Netstat gives important information about network socket and tcp state . This is very useful in

finding out the open , closed and waiting network tcp connection .

Network states returned by netstat are following :

CLOSED —- Closed. The socket is not being used.

LISTEN —- Listening for incoming connections.

SYN_SENT —- Actively trying to establish connection.

SYN_RECEIVED —- Initial synchronization of the connection under way.

ESTABLISHED —- Connection has been established.

CLOSE_WAIT —- Remote shut down; waiting for the socket to close.

FIN_WAIT_1 —- Socket closed; shutting down connection.

CLOSING —- Closed, then remote shutdown; awaiting acknowledgement.

LAST_ACK —- Remote shut down, then closed ;awaiting acknowledgement.

FIN_WAIT_2 —- Socket closed; waiting for shutdown from remote.

TIME_WAIT —- Wait after close for remote shutdown retransmission.

Example: # netstat -a

netstat -a

Local Address	Remote Address	Swind	Send-Q	Rwind	Recv-Q	State
*.*	*.*	0	0	24576	0	IDLE
*.22	*.*	0	0	24576	0	LISTEN
*.22	*.*	0	0	24576	0	LISTEN
*.*	*.*	0	0	24576	0	IDLE
*.32771	*.*	0	0	24576	0	LISTEN
*.4045	*.*	0	0	24576	0	LISTEN
*.25	*.*	0	0	24576	0	LISTEN
*.5987	*.*	0	0	24576	0	LISTEN
*.898	*.*	0	0	24576	0	LISTEN
*.32772	*.*	0	0	24576	0	LISTEN
*.32775	*.*	0	0	24576	0	LISTEN
*.32776	*.*	0	0	24576	0	LISTEN
*.*	*.*	0	0	24576	0	IDLE
192.168.1.184.22	192.168.1.186.50457	41992	0	24616	0	ESTABLISHED
192.168.1.184.22	192.168.1.186.56806	38912	0	24616	0	ESTABLISHED
192.168.1.184.22	192.168.1.183.58672	18048	0	24616	0	ESTABLISHED

if you see a lots of connections in FIN_WAIT state tcp/ip parameters have to be tuned because the connections are not being closed and they gets accumulating . After some time system may run out of resource . TCP parameter can be tuned to define a time out so that connections can be released and used by new connection.

Solaris Commands -

/usr/ucb/ps auxwww | less

prstat -a

Get CPU usages = ps -eo pcpu, pid,user,args | sort -k l -r | head -10

sar 1 10

List the top 10 CPU users.

ps -e -o pcpu -o pid -o user -o args | sort -k 1 | tail -21r

cksum <File_Name>

====

PS - 

Options of different types may be freely mixed.

Set the I_WANT_A_BROKEN_PS environment variable to force BSD syntax even when options are preceeded by a dash. The PS_PERSONALITY environment variable (described below) provides more detailed control of ps behavior.

SIMPLE PROCESS SELECTION

Switch Description

-A select all processes

-N negate selection

-a select all with a tty except session leaders

-d select all, but omit session leaders

-e select all processes

T select all processes on this terminal

a select all processes on a terminal, including those of other users

g really all, even group leaders (does nothing w/o SunOS settings)

r restrict output to running processes

x select processes without controlling ttys

--deselect negate selection

PROCESS SELECTION BY LIST

Switch Description

-C select by command name

-G select by RGID (supports names)

-U select by RUID (supports names)

-g select by session leader OR by group name

-p select by PID

-s select processes belonging to the sessions given

-t select by tty

-u select by effective user ID (supports names)

U select processes for specified users

p select by process ID

t select by tty

--Group select by real group name or ID

--User select by real user name or ID

--group select by effective group name or ID

--pid select by process ID

--sid select by session ID

--tty select by terminal

--user select by effective user name or ID

-123 implied --sid

123 implied --pid

OUTPUT FORMAT CONTROL

Switch Description

-O is preloaded "-o"

-c different scheduler info for -l option

-f does full listing

-j jobs format

-l long format

-o user-defined format

-y do not show flags; show rss in place of addr

O is preloaded "o" (overloaded)

X old Linux i386 register format

j job control format

l display long format

o specify user-defined format

s display signal format

u display user-oriented format

v display virtual memory format

--format user-defined format

OUTPUT MODIFIERS

Switch Description

-H show process hierarchy (forest)

-m show all threads

-n set namelist file

-w wide output

C use raw CPU time for %CPU instead of decaying average

N specify namelist file

O sorting order (overloaded)

S include some dead child process data (as a sum with the parent)

c true command name

e show environment after the command

f ASCII-art process hierarchy (forest)

h do not print header lines (repeat header lines in BSD personality)

m all threads

n numeric output for WCHAN and USER

w wide output

--cols set screen width

--columns set screen width

--cumulative include some dead child process data (as a sum with the parent)

--forest ASCII art process tree

--html HTML escaped output

--headers repeat header lines

--no-headers print no header line at all

--lines set screen height

--nul unjustified output with NULs

--null unjustified output with NULs

--rows set screen height

--sort specify sorting order

--width set screen width

--zero unjustified output with NULs

INFORMATION

Switch Description

-V print version

L list all format specifiers

V show version info

--help print help message

--info print debugging info

--version print version

OBSOLETE

Switch Description

A increase the argument space (DecUnix)

M use alternate core (try -n or N instead)

W get swap info from ... not /dev/drum (try -n or N instead)

k use /vmcore as c-dumpfile (try -n or N instead)