Linux for freshers

Friday, June 23, 2017

how to check list of opened and closed port in linux ?

There are different commands on both Linux and UNIX server to see what TCP/UDP ports are listening or open on your server. You can use netstat command, which prints network connections, routing tables, interface statistics, masquerade connections, and multicast memberships, etc.

Method 1:

netstat command to find open ports

Syntax :

netstat --listen

netstat -l

Example:

ravi@linuxforfreshers.com>>sudo netstat --listen

Active Internet connections (only servers)

Proto Recv-Q Send-Q Local Address Foreign Address State

tcp 0 0 *:1234 *:* LISTEN

tcp 0 0 *:8084 *:* LISTEN

tcp 0 0 192.168.122.1:domain *:* LISTEN

tcp 0 0 *:ssh *:* LISTEN

tcp 0 0 *:ipp *:* LISTEN

tcp 0 0 *:microsoft-ds *:* LISTEN

tcp 0 0 *:7070 *:* LISTEN

tcp 0 0 localhost:mysql *:* LISTEN

tcp 0 0 *:netbios-ssn *:* LISTEN

tcp6 0 0 [::]:ssh [::]:* LISTEN

tcp6 0 0 [::]:ipp [::]:* LISTEN

tcp6 0 0 [::]:microsoft-ds [::]:* LISTEN

tcp6 0 0 [::]:netbios-ssn [::]:* LISTEN

udp 0 0 *:39505 *:*

udp 0 0 *:ipp *:*

udp 0 0 *:mdns *:*

Active UNIX domain sockets (only servers)

Proto RefCnt Flags Type State I-Node Path

unix 2 [ ACC ] STREAM LISTENING 12950 /var/run/acpid.socket

unix 2 [ ACC ] STREAM LISTENING 18259042 @atpl-com.canonical.Unity.Scope.rhythmbox.T516689809663571

unix 2 [ ACC ] STREAM LISTENING 19096 /run/user/1000/keyring-n7CcyZ/control

unix 2 [ ACC ] STREAM LISTENING 22589 @/tmp/.ICE-unix/3779

unix 2 [ ACC ] STREAM LISTENING 21540 @/tmp/dbus-u6IauIGH5I

To display open ports and established TCP connections, enter:

netstat -vatn

Example:

Active Internet connections (servers and established)

Proto Recv-Q Send-Q Local Address Foreign Address State

tcp 0 0 0.0.0.0:1234 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:8084 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:631 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:445 0.0.0.0:* LISTEN

tcp 0 0 0.0.0.0:7070 0.0.0.0:* LISTEN

To display only open UDP ports try the following command:

netstat -vaun

Example:

ravi@linuxforfreshers.com>>sudo netstat -vaun

Active Internet connections (servers and established)

Proto Recv-Q Send-Q Local Address Foreign Address State

udp 0 0 0.0.0.0:39505 0.0.0.0:*

udp 0 0 0.0.0.0:631 0.0.0.0:*

Using netstat -lntu

Where

● -l = only services which are listening on some port

● -n = show port number, don't try to resolve the service name

● -t = tcp ports

● -u = udp ports

● -p = name of the program

Method 2:

Using lsof Command

To display the list of open ports, enter:

# lsof -i

To display all open files, use:

# lsof

To display all open IPv4 network files in use by the process whose PID is 10050, use:

# lsof -i 4 -a -p 10050

Another example:

# lsof -iTCP -sTCP:LISTEN

Method 3:

Using telnet

Quickest way to test if a TCP port is open (including any hardware firewalls you may have), is to type, from a remote computer (e.g. your desktop):

Syntax:

telnet hostip port_number

Example 1:

ravi@linuxforfreshers.com>>telnet 192.168.101.156 22

Trying 192.168.101.156...

Connected to 192.168.101.156

Escape character is '^]'.

Example 2:

ravi@linuxforfreshers.com>>telnet localhost 22

Trying 127.0.0.1...

Connected to localhost.

Method 3:

Using ss command

Syntax:

ss -lntu

Example:

ravi@linuxforfreshers.com>>ss -lntu

Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port

tcp UNCONN 0 0 *:39505 *:*

tcp UNCONN 0 0 *:631 *:*

tcp UNCONN 0 0 *:5353 *:*

Monday, June 19, 2017

How create Mysql User, Database and set privileges to user on linux?

How create Mysql User, Database and set privileges to user

[ravi@linuxforfreshers.com~]$ mysql –u root –p

password:

mysql> create user 'ravi'@'localhost' identified by '123456';

mysql> create database if not exists `ravidb`;

mysql> grant all on ravidb.* to ravi@linuxforfreshers.com identified by "123456" with grant option;

[ravi@linuxforfreshers.com~]$ mysql ravidb -u ravi -p

mysql> show databases;

mysql> use ravidb;

Friday, June 9, 2017

how to convert rpm to deb and deb to rpm using alien command on linux ?

You can use alien command to convert *.deb to *.rpm file. Also, if you have a *.rpm file that you want to install on a Debian or Ubuntu, you can convert the *.rpm to *.deb file using alien command as explained in this article.

Install alien command on Debian / Ubuntu

Install alien command on Ubuntu as shown below.

# sudo apt-get install alien

Install alien command on RHEL

You should check http://li.nux.ro/download/nux/dextop/el7/x86_64/ to see whether there’s a newer version before proceeding further:

#rpm -Uvh http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm

then do,

# yum update && yum install alien

1. Convert RPM to DEB

Use alien command to convert rpm to deb file

The following example converts the linuxconf-devel rpm file to linuxconf-devel deb file. Once you generate the deb file, you can install it on Ubuntu or Debian.

Example:

ravi@linuxforfreshers.com:~$ sudo alien -d --script -k anydesk-2.9.1-2.x86_64.rpm

anydesk_2.9.1-2_amd64.deb generated

Note: You'll also notice that alien has counted up the version number. If you want to keep the original version number, you must use the -k switch:

2. Convert DEB to RPM

Use alien to convert deb to rpm file

Use alient -r option to convert a deb file to rpm file. The following example converts libsox deb file to libsox rpm file. Once you generate the rpm file, you can install it on Red Hat, or CentOS.

Example:

ravi@linuxforfreshers.com:~/Downloads$ sudo alien -r anydesk_2.9.1-1_amd64.deb

Warning: Skipping conversion of scripts in package anydesk: postinst postrm

Warning: Use the --scripts parameter to include the scripts.

anydesk-2.9.1-2.x86_64.rpm generated

In above example i am not used -k so it will update the version automatically.

Example2:

ravi@linuxforfreshers.com:~$sudo alien -r --scripts -k anydesk_2.9.1-3_amd64.deb

anydesk-2.9.1-3.x86_64.rpm generated

Where -r, --to-rpm Generate a Red Hat rpm package

--scripts Include scripts in package.

-d, --to-deb Generate a Debian deb package (default).

-k, --keep-version Do not change version of generated package.

If u want more help check man alien.

Wednesday, May 24, 2017

how to find number of threads in a process on linux ?

The proc pseudo file system, which resides in /proc directory, is the easiest way to see the thread count of any active process. The /proc directory exports in the form of readable text files a wealth of information related to existing processes and system hardware such as CPU, interrupts, memory, disk, etc.

cat /proc/<pid>/status

Threads: <N>

For example Find the pid of the google chrome and find the each process using how many Threads.

root@linuxforfreshers.com:~# ps -ef | grep chrome

root 28168 20969 1 15:45 ? 00:00:17 /opt/google/chrome/chrome

Where 28168 is pid of google chrmoe.

root@linuxforfreshers.com:~# pidof chrome

28168

Example :

root@linuxforfreshers.com:~# cat /proc/28168/status

Name: chrome

State: S (sleeping)

Tgid: 28168

Ngid: 0

Pid: 28168

PPid: 20969

TracerPid: 0

Uid: 1000 1000 1000 1000

Gid: 1000 1000 1000 1000

FDSize: 256

Groups: 4 24 27 30 46 108 124 128 1000

NStgid: 28168 12008 1

NSpid: 28168 12008 1

NSpgid: 3938 0 0

NSsid: 3938 0 0

VmPeak: 1087572 kB

VmSize: 1028908 kB

VmLck: 0 kB

VmPin: 0 kB

VmHWM: 311332 kB

VmRSS: 212288 kB

VmData: 606664 kB

VmStk: 136 kB

VmExe: 109204 kB

VmLib: 45784 kB

VmPTE: 1676 kB

VmPMD: 620 kB

VmSwap: 8520 kB

HugetlbPages: 0 kB

Threads: 15

SigQ: 0/15451

SigPnd: 0000000000000000

ShdPnd: 0000000000000000

SigBlk: 0000000000000000

SigIgn: 0000000000001002

SigCgt: 00000001c0014efd

CapInh: 0000000000000000

CapPrm: 0000000000000000

CapEff: 0000000000000000

CapBnd: 0000003fffffffff

CapAmb: 0000000000000000

Seccomp: 2

Cpus_allowed: 3

Cpus_allowed_list: 0-1

Mems_allowed: 00000000,00000001

Mems_allowed_list: 0

voluntary_ctxt_switches: 32357

nonvoluntary_ctxt_switches: 18926

root@linuxforfreshers.com:~# cat /proc/28168/status | grep Threads

Threads: 15

Method 2: Using ls command

syntax:

ls /proc/<pid>/task | wc -l

This is because, for every thread created within a process, there is a corresponding directory created in /proc/<pid>/task, named with its thread ID. Thus the total number of directories in /proc/<pid>/task represents the number of threads in the process.

Example:

root@linuxforfreshers.com:~# ls /proc/28168/task/ | wc -l

Method 3: Using ps command

Syntax:

ps huH p <PID_OF_U_PROCESS> | wc -l

Example :

root@linuxforfreshers.com:~# ps huH p 28168 | wc -l

Method 4:

Syntax: ps -eT | grep <PID_of_process> | wc -l

Example :

root@linuxforfreshers.com:~# ps -eT | grep 28168 | wc -l

how to find which process is using highest memory(RAM) in linux ?

If you are running out of RAM on your Linux system, you will want to find the culprit in order to solve the problem, either by reconfiguring the RAM-hungry application or by stopping it.

Method 1:

ps aux | awk '{print $2, $4, $11}' | sort -k2rn | head -n 20

Example :

root@liuxforfrehers.com:~# ps aux | awk '{print $2, $4, $11}' | sort -k2rn | head -n 20

1551 12.7 /opt/google/chrome/chrome

21268 11.1 /opt/google/chrome/chrome

2068 7.1 /opt/google/chrome/chrome

21416 6.4 /opt/google/chrome/chrome

28168 6.2 /opt/google/chrome/chrome

21564 5.8 /opt/google/chrome/chrome

26696 5.5 /opt/google/chrome/chrome

20802 5.2 /opt/google/chrome/chrome

14806 4.9 /opt/google/chrome/chrome

2223 4.8 /opt/google/chrome/chrome

4134 4.5 compiz

17267 3.7 /opt/google/chrome/chrome

21231 3.1 /opt/google/chrome/chrome

28135 2.4 /opt/google/chrome/chrome

21025 2.2 /opt/google/chrome/chrome

4369 2.0 /usr/lib/x86_64-linux-gnu/zeitgeist-fts

17330 1.5 /opt/google/chrome/chrome

21126 1.4 /opt/google/chrome/chrome

1324 1.1 /usr/lib/policykit-1/polkitd

3932 1.0 /usr/lib/x86_64-linux-gnu/hud/hud-service

Method 2:

Show the processes memory in megabytes and the process path.

ps aux | awk '{print $6/1024 " MB\t\t" $11}' | sort -n

Method 3:

ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head

Example:

root@liuxforfrehers.com:~# ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head

PID PPID CMD %MEM %CPU

26696 20969 /opt/google/chrome/chrome - 21.6 1.8

1551 20969 /opt/google/chrome/chrome - 9.2 0.5

21268 20969 /opt/google/chrome/chrome - 9.0 1.4

2068 20969 /opt/google/chrome/chrome - 6.2 3.7

28168 20969 /opt/google/chrome/chrome - 5.0 1.1

20802 3680 /opt/google/chrome/chrome 4.8 3.9

21564 20969 /opt/google/chrome/chrome - 4.2 0.9

2223 20969 /opt/google/chrome/chrome - 4.0 5.1

4134 3938 compiz 3.8 2.3

Where pid is Process Id

Ppid is Parent Process Pid

%mem is Memory usage

%cpu is CPU usage