Multipath command with an examples

In linux operating system device mapping through multipath is widely used. Here, we can give you some example how we will use the multipath commands in Linux server

➤ Normally multipath device has a Word Wide Identifier (WWID), which is globally unique and unchanging.

➤ When new devices are brought under the control of DM-Multipath, the new devices may be seen in three different places under the /dev directory: /dev/mapper/mpathn, /dev/mpath/mpathn, and /dev/dm-n

➤ The devices in /dev/mapper are created early in the boot process. Use these devices to access the multipathed devices, for example when creating logical volumes.
The devices in /dev/mpath are provided as a convenience so that all multipathed devices can be seen in one directory. These devices are created by the udev device manager and may not be available on startup when the system needs to access them.

Note: Do not use these devices for creating logical volumes or filesystems

➤ Any devices of the form /dev/dm-n are for internal use only and should never be used.

Please find the multipath syntax which we used in the Linux operating system.


l    -> Display the current multipath configuration gathered from sysfs and the device mapper.

ll  -> Display the current multipath configuration gathered from sysfs, the device mapper, and all other available components on the system.

f    -> Remove the named multipath device.

F   -> Remove all unused multipath devices.

v   ->  Verbosity level
          . 0 no output
          . 1 print created devmap names only
          . 2 default verbosity
          . 3 print debug information

d   -> Dry run, do not create or update devmaps

r    -> Force devmap reload

⧪ How to display the current multipath configuration with all information.

[root@localhost~]# multipath -ll
Dec 21 11:27:17 | multipath.conf line 35, invalid keyword: selector
mpathf (3600c0ff00019e9e9dc94c25801000000) dm-6 HP,MSA 2040 SAN
size=466G features='0' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=70 status=active
  |- 1:0:0:4 sdg 8:96 active ready running
  |- 2:0:0:4 sdj 8:144 active ready running
  |- 1:0:1:4 sdq 65:0 active ready running
  `- 2:0:1:4 sdt 65:48 active ready running

⧪ How to remove multipath devices with multipath Command

[root@localhost~]# multipath -f mpathf

Note: if we use -F option then it is remove all unused devices.

⧪ How to Force reload device map with multipath Command

[root@localhost~]# multipath -r

Solaris Server process Monitoring tool- prstat

We have different type of tools and command which are used in Solaris or other Unix system to monitor the system process. But if we are talking about only Sun Solaris server then we have very good process tool which is called "prstat".

In this post, we will find that how prstat is work on the Solaris platform.

⇾   !-[solaris]# prstat

When you run the above command on the command line you will get the below output on the CLI screen which are refreshing in every few seconds and sorting all the information regarding the system resource.

  PID USERNAME  SIZE   RSS STATE  PRI NICE      TIME  CPU PROCESS/NLWP

 21322 root      11M 3236K cpu0    59    0   0:00:00 0.0% prstat/1

 21323 root      18M 4788K sleep   59    0   0:00:00 0.0% sshd/1

 22345 root      10M 2188K sleep   59    0   0:00:00 0.0% bash/1

   584 root       13M 3832K sleep   59    0   0:01:59 0.0% nscd/51

   154 root       13M 2068K sleep   59    0   0:00:00 0.0% syseventd/18

   183 root     1772K  776K sleep   59    0   0:00:13 0.0% utmpd/1

   538 root       11M 2572K sleep   59    0   0:00:00 0.0% picld/4

Total: 12 processes, 31 lwps, load averages: 0.00, 0.00, 0.00


This is a quick view of the prstat command but if you wanted to get a different view of the same info, like a summary of what users own these CPU consuming processes

⇾   !-[solaris]# prstat -a

If you run prstat with the -a option (prstat -a) you will get an output similar to the default one, but the last few lines of it will be used for providing a really useful report of the users consuming top system resources.


  PID USERNAME  SIZE   RSS STATE  PRI NICE      TIME  CPU PROCESS/NLWP

 21322 root      11M 3236K cpu0    59    0   0:00:00 0.0% prstat/1

 21323 root      18M 4788K sleep   59    0   0:00:00 0.0% sshd/1

 22345 root      10M 2188K sleep   59    0   0:00:00 0.0% bash/1


 NPROC USERNAME  SWAP   RSS MEMORY      TIME  CPU

     5 root      52M   13M   1.3%   0:00:00 0.0%

    50 root      841M  571M    56%   0:22:22 0.0%

     2 daemon     17M 4520K   0.4%   0:00:04 0.0%

Total: 12 processes, 31 lwps, load averages: 0.00, 0.00, 0.00

We have different type of syntax which we can used to monitor the Solaris server process which are listed below.

!-[solaris]# prstat -L  -> This shows thread per line instead of one process per line
!-[solaris]# prstat -s -> prstat output can be sorted using set of sub-options .sub options are                  cpu,pri,rss,size,time 

!-[solaris]# prstat -t  -> It provides complete users resource utilization.
!-[solaris]# prstat -Z  -> It provides summary per local zone.

How to check number of CPU and processor in linux operating system

In this post, we will find all the command using which we can find that how many CPU and processor are used in Linux operating system.

⇾ This command are applicable in both RedHat & CentOS operating machine.

➤ How to check number of processor on operating system.

      cat /proc/cpuinfo | grep "physical id" | sort -u | wc -l

   Using above command it show you the number of processor which are currently used on server.

➤ How to check number of cores on Linux operating system.

     cat /proc/cpuinfo | grep "core id" | sort -u | wc -l

➤ You can used other command as well like "lscpu" to check number of processor and core per socket.

➤ Please find the other command which are also used to check the number of processor and cores in  Linux operating system.

    cat /proc/cpuinfo | grep 'model name' | uniq
   cat /proc/cpuinfo | grep "physical id" | sort -u | wc -l
   cat /proc/cpuinfo | grep "core id" | sort -u | wc -l

How to change a disk in SVM Solaris volume manager

In this post, I will take my sparc server machine. My Sun Sparc server consist 2 hard disk, let us assume the server has 2 hard disk: c0t0d0 and c0t1d0. We will assume c0t0d0 failed and need to be replaced.

Step by Step Method as described below:

1. In the initial step, we will find that which hard disk is down or faulty. To check this we will used "format" command.

!-[solaris]## format
       0. c0t0d0 <__drive type unknown__>
          /pci@0,600000/pci@0/pci@8/pci@0/scsi@1/sd@0,0
       1. c0t1d0 <SUN146G cyl 14087 alt 2 hd 24 sec 848>
          /pci@0,600000/pci@0/pci@8/pci@0/scsi@1/sd@1,0

If you see the "format" command output, we have two disk "c0t0d0,c0t1d0". Disk "c0t0d0" is in faulty state and it's down, You can see the drive type is in unknown state.

2. If you are running the "metastat" command you can see the status of hard disk which is show status in "need maintenance".

!-[solaris]## metastat    # will show status in "need maintenance"

        flags           first blk       block count
     a        u         16              8192            /dev/dsk/c0t0d0s7
     a        u         8208            8192            /dev/dsk/c0t0d0s7
     a    p  luo        16              8192            /dev/dsk/c0t1d0s7
     a    p  luo        8208            8192            /dev/dsk/c0t1d0s7

!-[solaris]## metadb -d c0t0d0s7
!-[solaris]## metadb

Using above command we delete metadb on failing disk and check that metadb on the other disk.

4. Now, we will unconfigure the corresponding disk which is down right now. This is the main step of this post so you can more careful while running the command which is given below.

!-[solaris]## cfgadm -al
!-[solaris]## cfgadm -f -c unconfigure c0::dsk/c0t0d0
!-[solaris]## cfgadm -al

Using cfgadm command we will unconfigure the c0t0d0 faulty hard disk so that we will replace the down hard disk in next step.

5. Now you can change the faulty disk to new one and reconfigure it again with same name.

!-[solaris]## cfgadm -c configure c0::dsk/c0t0d0
!-[solaris]## cfgadm -al

6. In this steo we will duplicate partitionning schema of first disk to the second and create metadb.

!-[solaris]## prtvtoc /dev/rdsk/c0t1d0s2 | fmthard -s - /dev/rdsk/c0t0d0s2
!-[solaris]## metadb -a -f -c2 /dev/dsk/c0t0d0s7

7. In second last step you will run all the below command for replacement of the failinf SVM partition.

!-[solaris]## metastat
!-[solaris]## metareplace -ef d4 c0t0d0s4
!-[solaris]## metareplace -ef d3 c0t0d0s3
!-[solaris]## metareplace -ef d1 c0t0d0s1
!-[solaris]## metareplace -ef d0 c0t0d0s0
!-[solaris]## metareplace -ef d5 c0t0d0s5
!-[solaris]## metareplace -ef d6 c0t0d0s6
!-[solaris]## metasync d0
!-[solaris]## metasync d1
!-[solaris]## metasync d3
!-[solaris]## metasync d4
!-[solaris]## metasync d5
!-[solaris]## metasync d6
!-[solaris]## metasync d7

8. In final step you need to make the disk bootable so that operating system will be boot on the mirror disk.

!-[solaris]## installboot /usr/platform/`uname -i`/lib/fs/ufs/bootblk /dev/rdsk/c0t0d0s0

Using this step you can make a disk bootable. I hope this post is useful for you. You are requested to please comment on the post if you have any issue, I will try to back you with my answer.

Useful SQL command for MySQL database on Linux Operating System

This post related to MySQL database SQL command which is used in daily database work by database administrator.

Please find the below points which is very useful to database admin on Linux operating system.

➤ How to create new database:

 CREATE DATABASE <DATABASENAME>;

 e.g. CREATE DATABASE XYZ;

In this example I have created the "XYZ" named database, you can replace database name according to your choice.

➤ How to create mater user with all level access to all available databases:

 GRANT ALL ON *.* TO <USERNAME> IDENTIFIED BY '<PASSWORD>';
 e.g.  GRANT ALL ON *.* TO TESTDBUSER IDENTIFIED BY 'TESTDBUSER';

In this example I used "testdbuser" MySQL user on the server.

➤ How to take backup (dump) of a database:

For this command you need not to login into the database. Once you login on the database please run the below command to take a dump of server.

 mysqldump --lock-all-tables -u <USERNAME> -p -h <DATABASESERVERNAME/IP ADDRESS> <DATABASENAME> > <NEWDUMPFILENAME>.sql

 e.g. mysqldump --lock-all-tables -u ABC -p -h MACHINE1 XYZ > XYZ_16022017.sql

After this command you have to provide DB password only and dump will be done in the folder in which u are working currently.

➤ How to take backup (dump) of a table's:

For this command you need not to login into the database.

 mysqldump -u <USERNAME> -p <DATABASENAME> <TABLENAME> > <NEWDUMPFILENAME>.sql

 e.g. mysqldump -u testdbuser -p testdb test_book > test.sql

After this command you have to provide DB password only and dump will be done in the folder in which u are working currently. for dumping multiple table use space between the table names.

➤ How to run a database dump to another machine:

Go to the folder in which sql dump file is placed and then connect with your Database in which you want to run dump and then run below command.

 source <FILENAME>.sql;

 e.g source XYZ_16022017.sql;

➤ How to take dump only triggers and procedure from database:

 mysqldump --routines --no-create-info --no-data --no-create-db --skip-opt -u <USERNAME> -p <DATABASENAME> > <NEWDUMPFILENAME>.sql

 e.g. mysqldump --routines --no-create-info --no-data --no-create-db --skip-opt -u TESTDBSUER -p XYZ > XYZ_16022017.sql

After this command you have to provide DB password only and dump will be done in the folder in which u are working currently.

➤ How to show procedure/function code:

 SHOW CREATE PROCEDURE <STORED PROCEDURE/FUNCTION NAME>\G

 e.g. SHOW CREATE PROCEDURE FLIGHT_INVOICETOSAP\G;

How to increase filed width of a table attribute:

 ALTER TABLE <TABLENAME> CHANGE <EXISTING_FIELD_NAME> <NEW_FIELD_NAME> <DATATYPE>(<NEW_FIELD_WIDTH>);

 e.g. ALTER TABLE TRILOK CHANGE PASSENGER_NO PASSENGER_NUMBER VARCHAR(30);

field name and data type change is not recommended.

➤ How to display all existing databases:

 SHOW DATABASES;

Using this command you can show all the created database list on the Linux server.

How to display all existing tables:

 SHOW TABLES;
 SHOW TABLES LIKE '<CHARACTERS>%';

Using this command you can check all the tables which is created on the database.

➤ How to recover a MySQL root password:

This is one of the best way to recover the MySQL root password if you forget. I always used below method to reset the root password.
Stop the MySQL server process.

  # /etc/init.d/mysql stop
Start again with no grant tables.

  # mysqld_safe --skip-grant-tables &
Login to MySQL as root. Set new password.

  # mysql -u root
  mysql> use mysql;
  mysql> update user set password=PASSWORD("newrootpassword") where User='root';
  mysql> flush privileges;
  mysql> quit
Exit MySQL and restart MySQL server.

  # /etc/init.d/mysql stop
  # /etc/init.d/mysql start
Set a root password if there is on root password.

  # mysqladmin -u root password newpassword
Update a root password.

  # mysqladmin -u root -p oldpassword newpassword

➤ How to grant privileges to a user:

If we need to provide the privileges to user we will use below two method. I will describe the step by step method for this one.

METHOD 1

Allow the user "bob" to connect to the server from localhost using the password "passwd". Login as root. Switch to the MySQL db. Give privs. Update privs.

  # mysql -u root -p
  mysql> use mysql;
  mysql> grant usage on *.* to bob@localhost identified by 'passwd';
  mysql> flush privileges;

Give user privileges for a db. Login as root. Switch to the MySQL db. Grant privs. Update privs.

  # mysql -u root -p
  mysql> use mysql;
  mysql>INSERT INTO user (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,Create_priv,Drop_priv) VALUES ('%','databasename','username','Y','Y','Y','Y','Y','N');
  mysql> flush privileges;

METHOD 2

  mysql> grant all privileges on databasename.* to username@localhost;
  mysql> flush privileges;

To update info already in a table.

Load a CSV file into a table:

 mysql> LOAD DATA INFILE '/tmp/filename.csv' replace INTO TABLE [table name] FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n' (field1,field2,field3);

➤ Dump all databases for backup:

Backup file is SQL commands to recreate all databases.

  # [mysql dir]/bin/mysqldump -u root -ppassword --opt >/tmp/alldatabases.sql

Dump one database for backup.

  # [mysql dir]/bin/mysqldump -u username -p password --databases databasename >/tmp/databasename.sql

Dump a table from a database.

  # [mysql dir]/bin/mysqldump -c -u username -p password databasename tablename > /tmp/databasename.tablename.sql

➤ Restore database (or database table) from backup.

  # [mysql dir]/bin/mysql -u username -p password databasename < /tmp/databasename.sql
  Create Table Example 1.

Using above method we can take database back very fast. I hope through this post you can easily able to create MySQL database, MySQL dump, table creation etc work.

Solaris zone: error: net0: failed to create VNIC: operation not supported

In this post, I will discuss with you one of the most interesting error which I am facing when I boot the local zone on Solaris 11.3. The description of this interesting issue as describe below.

Description of error:

!-[solaris]# zoneadm -z sun01 boot

zone 'sun01': error: net0: failed to create VNIC: operation not supported

zoneadm: zone sun01: call to zoneadmd(1M) failed: zoneadmd(1M

I have try to create and configure the  VNIC on Solaris 11.3 operating server but it get failed with the same error.

!-[solaris]#dladm create-vnic -l net0 vnic01

dladm: vnic creation failed: operation not supported

If you are also facing a such error while booting the local zone on solaris 11 server, then please use the below solution to resolve such issues.

Solution of error:

➥ This error "failed to create VNIC: operation not supported" would normally come when there are not enough mac addresses to assign to the zone. So now we need to add alternate mac addresses to the network interface.So before adding the new mac address we will stop LDM.

!-[solaris]#ldm list-domain

NAME            STATE     FLAGS  CONS   VCPU MEMORY  UTIL NORM UPTIME

primary         active    -n-cv- UART   8    8G      2.0% 2.0% 41d 20h 14m

0004fb0000060000ff1d3d8336112f6f active    -n---- 5001   50   64G     0.1% 0.1% 18h 23m

➥ Now log in to the Solaris global zone and check if net0 have additional MAC addresses or not. Please use the below command to check the status.

!-[solaris]# dladm show-phys -m

LINK               SLOT    ADDRESS           INUSE CLIENT

net0               primary 0:21:f6:d6:d3:e5  yes  net0

                   1       0:14:4f:f9:6d:8d  no   --

                   2       0:14:4f:fb:10:2b  no   --

                   3       0:14:4f:f9:41:d6  no   --

                   4       0:14:4f:f8:dd:c8  no   --

net1               primary 0:21:f6:51:be:4d  yes  net1

➥ Now zone will start without any issue, as we have assigned the new mac address to this zone.

!-[solaris]# zoneadm -z sun01 start

Please let me know if you are facing any issue regarding this error.

How to mount CIFS file system on Linux Operating Server

Step by Step method for Mount CIFS on Linux Server:

➤ In the initial step we will gather all rpm's or packages information which is required for CIFS file system.

[root@localhost]# rpm -qa | grep cifs 

cifs-utils-4.8.1-20.el6.x86_64

if you see the above output, this packages is required for CIFS file system on Linux system. So you can install this rpm using rpm command if you have rpm packages on the server otherwise you will install the packages using YUM utility.

[root@localhost]#rpm -ivh cifs-utils-4.8.1-20.el6.x86_64.rpm

if you are using YUM, then please install the packages using below command.

[root@localhost]#yum install cifs-utils*

it is installed all required dependency related to CIFS file system.

➤ In this step, we will create the mount point on the server where we need to mount the CIFS file system.

[root@localhost]# mkdir -p /backup/cifs

We will create the above mount directory where i will mount the file system.

➤ Now, we will create a CIFS user and assign a password so the user can access mount folder.

[root@localhost]# touch /etc/cifspasswd

[root@localhost]# chmod 600 /etc/cifspasswd

[root@localhost]#vi /etc/cifspasswd

user=castwebsvc

password=*******

➤ In this step we need to make a permanent entry of mounted file system so once we reboot the machine mounted file system not umount.

[root@localhost]# vi /etc/fstab

ADD fstab entry :

//WindowsServer/share /mount/point cifs rw,mand,user=USER,password=PASS 0 0

Example :

//192.168.0.1/CAST_data4/AICCodeUpload  /backup/cifs cifs   rw,mand,credentials=/etc/cifspasswd         0 0

You can take an example for your system. Please change the mount point as per your requirement.

➤ In the final step you need to mount the file system using below command.

[root@localhost]# mount /backup/cifs

[root@localhost]# mount -a

Using above command the CIFS file system has been mounted successfully.