Dynamic SAN fabric reconfiguration

There are several methods that you can use to force the Linux operating system to recognize disks that are added or removed from the fabric.

When you add or remove disks from the fabric, you can use any of the following methods to force the Linux host to recognize these changes:

1. Rescan the SCSI bus by restarting the host.
2. Rescan the SCSI bus by unloading and reloading the host adapter driver.
3. Rescan the bus by echoing the /sys filesystem (Linux 2.6 kernels only).
4. Manually add and remove SCSI disks by echoing the /proc or /sys filesystem.

Because devices are discovered by scanning the SCSI bus, it is typically easiest to rescan the SCSI bus to detect any SAN fabric changes.

Rescan the bus by restarting the host or by unloading and reloading the host adapter driver

A bus rescan is automatically triggered by restarting the system or reloading the host adapter driver.

Reloading the host adapter driver assumes that the host adapter driver is built as a module. Restarting the system works whether the driver is compiled in the kernel or as a module.

Before performing these tasks, you must:

1. Stop all I/O.
2. Unmount all file systems.
3. If SDD is being used, unload the SDD driver with the sdd stop command before reloading the host adapter driver. After the host adapter driver is reloaded, reload SDD with the sdd start command.

Rescan the bus by echoing the /sys filesystem

For Linux 2.6 kernels only, a rescan can be triggered through the /sys interface without having to unload the host adapter driver or restart the system. The following command scans all channels, targets, and LUNs on host H.

echo “- - -” > /sys/class/scsi_host/hostH/scan

Manually add and remove SCSI disks by echoing the /proc or /sys filesystem

You can use the following commands to manually add and remove SCSI disk.

Note: In the following command examples, H, B, T, L, are the host, bus, target, and LUN IDs for the device.

You can unconfigure and remove an unused SCSI disk with the following command:

• echo "scsi remove-single-device H B T L" > /proc/scsi/scsi

• If the driver cannot be unloaded and loaded again, and you know the host, bus, target and LUN IDs for the new devices, you can add them through the /proc/scsi/scsi file using the following command:
• echo "scsi add-single-device H B T L" > /proc/scsi/scsi

For Linux 2.6 kernels, devices can also be added and removed through the /sys filesystem. Use the following command to remove a disk from the kernel’s recognition:

• echo “1” > /sys/class/scsi_host/hostH/device/H:B:T:L/delete
• or, as a possible variant on other 2.6 kernels, you can use the command:
• echo “1” > /sys/class/scsi_host/hostH/device/targetH:B:T/H:B:T:L/delete

To reregister the disk with the kernel use the command:

• echo “B T L” > /sys/class/scsi_host/hostH/scan

Note: The Linux kernel does not assign permanent names for the fabric devices in the /dev directory. Device file names are assigned in the order in which devices are discovered during the bus scanning. For example, a LUN might be /dev/sda. After a driver reload, the same LUN might become /dev/sdce. A fabric reconfiguration might also result in a shift in the host, bus, target and LUN IDs, which makes it unreliable to add specific devices through the /proc/scsi/scsi file.

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LUN identification for the Linux host system

LUN identification for the Linux host system

This topic describes LUN identification for the Linux host system.

In Linux 2.4 kernels, SCSI devices are discovered by scanning the SCSI bus when the host adapter driver is loaded. A list of devices which have been discovered and are recognized by the SCSI subsystem are listed in /proc/scsi/scsi. It is good practice to use the cat command to display the output of /proc/scsi/scsi to verify that the correct number of LUNs has been recognized by the kernel.

The following is example output:


# cat proc/scsi/scsi
# cat /proc/scsi/scsi | less
Attached devices:
Host: scsi1 Channel: 00 Id: 02 Lun: 00
Vendor: IBM Model: 2107900 Rev: .248
Type: Direct-Access ANSI SCSI revision: 05
Host: scsi1 Channel: 00 Id: 02 Lun: 01
Vendor: IBM Model: 2107900 Rev: .248
Type: Direct-Access ANSI SCSI revision: 05
Host: scsi1 Channel: 00 Id: 03 Lun: 00
Vendor: IBM Model: 2107900 Rev: 5.53
Type: Direct-Access ANSI SCSI revision: 05
Host: scsi1 Channel: 00 Id: 03 Lun: 01
Vendor: IBM Model: 2107900 Rev: 5.53
Type: Direct-Access ANSI SCSI revision: 05

Note: The /proc/scsi/scsi list of devices is not dynamic and does not reflect state changes caused by fabric changes. Please see the section on “Dynamic SAN fabric reconfiguration' for more information on how to deal with fabric changes.



Starting with the Linux 2.6 kernels, the /proc filesystem is migrating over to the improved /sys filesystem. The /sys filesystem supports dynamic changes such as adding and removing LUNs without requiring a host adapter driver reload or restarting the host system. Typically, more accurate information about what SCSI devices are recognized by the host system is attained by checking the contents of the directory /sys/class/scsi_host/hostN, where N is host adapter ID number. lsscsi is a user-space tool that uses the information in /sys to display a summarized list of all the recognized devices. This tool may not currently be available on all Linux 2.6 distribution kernels.

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50 Most Frequently Used UNIX / Linux Commands (With Examples)

50 Most Frequently Used UNIX / Linux Commands (With Examples)

　
1. tar command examples
Create a new tar archive.
$ tar cvf archive_name.tar dirname/
Extract from an existing tar archive.
$ tar xvf archive_name.tar
View an existing tar archive.
$ tar tvf archive_name.tar
　
2. grep command examples
Search for a given string in a file (case in-sensitive search).
$ grep -i "the" demo_file
Print the matched line, along with the 3 lines after it.
$ grep -A 3 -i "example" demo_text
Search for a given string in all files recursively
$ grep -r "ramesh" *
　
3. find command examples
Find files using file-name ( case in-sensitve find)
# find -iname "MyCProgram.c"
Execute commands on files found by the find command
$ find -iname "MyCProgram.c" -exec md5sum {} \;
Find all empty files in home directory
# find ~ -empty
More find examples: Mommy, I found it! — 15 Practical Linux Find Command Examples
4. ssh command examples
Login to remote host
ssh -l jsmith remotehost.example.com
Debug ssh client
ssh -v -l jsmith remotehost.example.com
Display ssh client version
$ ssh -V
OpenSSH_3.9p1, OpenSSL 0.9.7a Feb 19 2003
More ssh examples: 5 Basic Linux SSH Client Commands
5. sed command examples
When you copy a DOS file to Unix, you could find \r\n in the end of each line. This example converts the DOS file format to Unix file format using sed command.
$sed 's/.$//' filename
Print file content in reverse order
$ sed -n '1!G;h;$p' thegeekstuff.txt
Add line number for all non-empty-lines in a file
$ sed '/./=' thegeekstuff.txt sed 'N; s/\n/ /'
More sed examples: Advanced Sed Substitution Examples
6. awk command examplesRemove duplicate lines using awk
$ awk '!($0 in array) { array[$0]; print }' temp
Print all lines from /etc/passwd that has the same uid and gid
$awk -F ':' '$3==$4' passwd.txt
Print only specific field from a file.
$ awk '{print $2,$5;}' employee.txt
More awk examples: 8 Powerful Awk Built-in Variables – FS, OFS, RS, ORS, NR, NF, FILENAME, FNR
7. vim command examples
Go to the 143rd line of file
$ vim +143 filename.txt
Go to the first match of the specified
$ vim +/search-term filename.txt
Open the file in read only mode.
$ vim -R /etc/passwd
More vim examples: How To Record and Play in Vim Editor
8. diff command examples
Ignore white space while comparing.
# diff -w name_list.txt name_list_new.txt
2c2,3
< John Doe --- > John M Doe
> Jason Bourne
More diff examples: Top 4 File Difference Tools on UNIX / Linux – Diff, Colordiff, Wdiff, Vimdiff
9. sort command examples
Sort a file in ascending order
$ sort names.txt
Sort a file in descending order
$ sort -r names.txt
Sort passwd file by 3rd field.
$ sort -t: -k 3n /etc/passwd more
10. export command examples
To view oracle related environment variables.
$ export grep ORACLE
declare -x ORACLE_BASE="/u01/app/oracle"
declare -x ORACLE_HOME="/u01/app/oracle/product/10.2.0"
declare -x ORACLE_SID="med"
declare -x ORACLE_TERM="xterm"
To export an environment variable:
$ export ORACLE_HOME=/u01/app/oracle/product/10.2.0
11. xargs command examples
Copy all images to external hard-drive
# ls *.jpg xargs -n1 -i cp {} /external-hard-drive/directory
Search all jpg images in the system and archive it.
# find / -name *.jpg -type f -print xargs tar -cvzf images.tar.gz
Download all the URLs mentioned in the url-list.txt file
# cat url-list.txt xargs wget –c
12. ls command examples
Display filesize in human readable format (e.g. KB, MB etc.,)
$ ls -lh
-rw-r----- 1 ramesh team-dev 8.9M Jun 12 15:27 arch-linux.txt.gz
Order Files Based on Last Modified Time (In Reverse Order) Using ls -ltr
$ ls -ltr
Visual Classification of Files With Special Characters Using ls -F
$ ls -F
More ls examples: Unix LS Command: 15 Practical Examples
13. pwd command
pwd is Print working directory. What else can be said about the good old pwd who has been printing the current directory name for ages.
14. cd command examples
Use "cd -" to toggle between the last two directories
Use "shopt -s cdspell" to automatically correct mistyped directory names on cd
More cd examples: 6 Awesome Linux cd command Hacks
15. gzip command examples
To create a *.gz compressed file:
$ gzip test.txt
To uncompress a *.gz file:
$ gzip -d test.txt.gz
Display compression ratio of the compressed file using gzip -l
$ gzip -l *.gz
compressed uncompressed ratio uncompressed_name
23709 97975 75.8% asp-patch-rpms.txt
16. bzip2 command examples
To create a *.bz2 compressed file:
$ bzip2 test.txt
To uncompress a *.bz2 file:
bzip2 -d test.txt.bz2
More bzip2 examples: BZ is Eazy! bzip2, bzgrep, bzcmp, bzdiff, bzcat, bzless, bzmore examples
17. unzip command examplesTo extract a *.zip compressed file:
$ unzip test.zip
View the contents of *.zip file (Without unzipping it):
$ unzip -l jasper.zip
Archive: jasper.zip
Length Date Time Name
-------- ---- ---- ----
40995 11-30-98 23:50 META-INF/MANIFEST.MF
32169 08-25-98 21:07 classes_
15964 08-25-98 21:07 classes_names
10542 08-25-98 21:07 classes_ncomp
18. shutdown command examples
Shutdown the system and turn the power off immediately.
# shutdown -h now
Shutdown the system after 10 minutes.
# shutdown -h +10
Reboot the system using shutdown command.
# shutdown -r now
Force the filesystem check during reboot.
# shutdown -Fr now
19. ftp command examples
Both ftp and secure ftp (sftp) has similar commands. To connect to a remote server and download multiple files, do the following.
$ ftp IP/hostname
ftp> mget *.html
To view the file names located on the remote server before downloading, mls ftp command as shown below.
ftp> mls *.html -
/ftptest/features.html
/ftptest/index.html
/ftptest/othertools.html
/ftptest/samplereport.html
/ftptest/usage.html
More ftp examples: FTP and SFTP Beginners Guide with 10 Examples
20. crontab command examples
View crontab entry for a specific user
# crontab -u john -l
Schedule a cron job every 10 minutes.
*/10 * * * * /home/ramesh/check-disk-space
More crontab examples: Linux Crontab: 15 Awesome Cron Job Examples
21. service command examples
Service command is used to run the system V init scripts. i.e Instead of calling the scripts located in the /etc/init.d/ directory with their full path, you can use the service command.
Check the status of a service:
# service ssh status
Check the steatus of all the services.
service --status-all
Restart a service.
# service ssh restart
22. ps command examples
ps command is used to display information about the processes that are running in the system.
While there are lot of arguments that could be passed to a ps command, following are some of the common ones.
To view current running processes.
$ ps -ef more
To view current running processes in a tree structure. H option stands for process hierarchy.
$ ps -efH more
23. free command examples
This command is used to display the free, used, swap memory available in the system.
Typical free command output. The output is displayed in bytes.
$ free
total used free shared buffers cached
Mem: 3566408 1580220 1986188 0 203988 902960
-/+ buffers/cache: 473272 3093136
Swap: 4000176 0 4000176
If you want to quickly check how many GB of RAM your system has use the -g option. -b option displays in bytes, -k in kilo bytes, -m in mega bytes.
$ free -g
total used free shared buffers cached
Mem: 3 1 1 0 0 0
-/+ buffers/cache: 0 2
Swap: 3 0 3
If you want to see a total memory ( including the swap), use the -t switch, which will display a total line as shown below.
ramesh@ramesh-laptop:~$ free -t
total used free shared buffers cached
Mem: 3566408 1592148 1974260 0 204260 912556
-/+ buffers/cache: 475332 3091076
Swap: 4000176 0 4000176
Total: 7566584 1592148 5974436
24. top command examples
top command displays the top processes in the system ( by default sorted by cpu usage ). To sort top output by any column, Press O (upper-case O) , which will display all the possible columns that you can sort by as shown below.
Current Sort Field: P for window 1:Def
Select sort field via field letter, type any other key to return
a: PID = Process Id v: nDRT = Dirty Pages count
d: UID = User Id y: WCHAN = Sleeping in Function
e: USER = User Name z: Flags = Task Flags
........
To displays only the processes that belong to a particular user use -u option. The following will show only the top processes that belongs to oracle user.
$ top -u oracle
More top examples: Can You Top This? 15 Practical Linux Top Command Examples
25. df command examples
Displays the file system disk space usage. By default df -k displays output in bytes.
$ df -k
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 29530400 3233104 24797232 12% /
/dev/sda2 120367992 50171596 64082060 44% /home
df -h displays output in human readable form. i.e size will be displayed in GB’s.
ramesh@ramesh-laptop:~$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 29G 3.1G 24G 12% /
/dev/sda2 115G 48G 62G 44% /home
Use -T option to display what type of file system.
ramesh@ramesh-laptop:~$ df -T
Filesystem Type 1K-blocks Used Available Use% Mounted on
/dev/sda1 ext4 29530400 3233120 24797216 12% /
/dev/sda2 ext4 120367992 50171596 64082060 44% /home
26. kill command examples
Use kill command to terminate a process. First get the process id using ps -ef command, then use kill -9 to kill the running Linux process as shown below. You can also use killall, pkill, xkill to terminate a unix process.
$ ps -ef grep vim
ramesh 7243 7222 9 22:43 pts/2 00:00:00 vim
$ kill -9 7243
More kill examples: 4 Ways to Kill a Process – kill, killall, pkill, xkill
27. rm command examples
Get confirmation before removing the file.
$ rm -i filename.txt
It is very useful while giving shell metacharacters in the file name argument.
Print the filename and get confirmation before removing the file.
$ rm -i file*
Following example recursively removes all files and directories under the example directory. This also removes the example directory itself.
$ rm -r example
28. cp command examples
Copy file1 to file2 preserving the mode, ownership and timestamp.
$ cp -p file1 file2
Copy file1 to file2. if file2 exists prompt for confirmation before overwritting it.
$ cp -i file1 file2
29. mv command examples
Rename file1 to file2. if file2 exists prompt for confirmation before overwritting it.
$ mv -i file1 file2
Note: mv -f is just the opposite, which will overwrite file2 without prompting.
mv -v will print what is happening during file rename, which is useful while specifying shell metacharacters in the file name argument.
$ mv -v file1 file2
30. cat command examples
You can view multiple files at the same time. Following example prints the content of file1 followed by file2 to stdout.
$ cat file1 file2
While displaying the file, following cat -n command will prepend the line number to each line of the output.
$ cat -n /etc/logrotate.conf
1 /var/log/btmp {
2 missingok
3 monthly
4 create 0660 root utmp
5 rotate 1
6 }
31. mount command examples
To mount a file system, you should first create a directory and mount it as shown below.
# mkdir /u01
# mount /dev/sdb1 /u01
You can also add this to the fstab for automatic mounting. i.e Anytime system is restarted, the filesystem will be mounted.
/dev/sdb1 /u01 ext2 defaults 0 2
32. chmod command exampleschmod command is used to change the permissions for a file or directory.
Give full access to user and group (i.e read, write and execute ) on a specific file.
$ chmod ug+rwx file.txt
Revoke all access for the group (i.e read, write and execute ) on a specific file.
$ chmod g-rwx file.txt
Apply the file permissions recursively to all the files in the sub-directories.
$ chmod -R ug+rwx file.txt
More chmod examples: 7 Chmod Command Examples for Beginners
33. chown command examples
chown command is used to change the owner and group of a file. \
To change owner to oracle and group to db on a file. i.e Change both owner and group at the same time.
$ chown oracle:dba dbora.sh
Use -R to change the ownership recursively.
$ chown -R oracle:dba /home/oracle
34. passwd command examplesChange your password from command line using passwd. This will prompt for the old password followed by the new password.
$ passwd
Super user can use passwd command to reset others password. This will not prompt for current password of the user.
# passwd USERNAME
Remove password for a specific user. Root user can disable password for a specific user. Once the password is disabled, the user can login without entering the password.
# passwd -d USERNAME
35. mkdir command examples
Following example creates a directory called temp under your home directory.
$ mkdir ~/temp
Create nested directories using one mkdir command. If any of these directories exist already, it will not display any error. If any of these directories doesn’t exist, it will create them.
$ mkdir -p dir1/dir2/dir3/dir4/
36. ifconfig command examplesUse ifconfig command to view or configure a network interface on the Linux system.
View all the interfaces along with status.
$ ifconfig -a
Start or stop a specific interface using up and down command as shown below.
$ ifconfig eth0 up
$ ifconfig eth0 down
More ifconfig examples: Ifconfig: 7 Examples To Configure Network Interface
37. uname command examples
Uname command displays important information about the system such as — Kernel name, Host name, Kernel release number,Processor type, etc.,
Sample uname output from a Ubuntu laptop is shown below.
$ uname -a
Linux john-laptop 2.6.32-24-generic #41-Ubuntu SMP Thu Aug 19 01:12:52 UTC 2010 i686 GNU/Linux
38. whereis command examples
When you want to find out where a specific Unix command exists (for example, where does ls command exists?), you can execute the following command.
$ whereis ls
ls: /bin/ls /usr/share/man/man1/ls.1.gz /usr/share/man/man1p/ls.1p.gz
When you want to search an executable from a path other than the whereis default path, you can use -B option and give path as argument to it. This searches for the executable lsmk in the /tmp directory, and displays it, if it is available.
$ whereis -u -B /tmp -f lsmk
lsmk: /tmp/lsmk
39. whatis command examples
Whatis command displays a single line description about a command.
$ whatis ls
ls (1) - list directory contents
$ whatis ifconfig
ifconfig (8) - configure a network interface
40. locate command examples
Using locate command you can quickly search for the location of a specific file (or group of files). Locate command uses the database created by updatedb.
The example below shows all files in the system that contains the word crontab in it.
$ locate crontab
/etc/anacrontab
/etc/crontab
/usr/bin/crontab
/usr/share/doc/cron/examples/crontab2english.pl.gz
/usr/share/man/man1/crontab.1.gz
/usr/share/man/man5/anacrontab.5.gz
/usr/share/man/man5/crontab.5.gz
/usr/share/vim/vim72/syntax/crontab.vim
41. man command examples
Display the man page of a specific command.
$ man crontab
When a man page for a command is located under more than one section, you can view the man page for that command from a specific section as shown below.
$ man SECTION-NUMBER commandname
Following 8 sections are available in the man page.
General commands
System calls
C library functions
Special files (usually devices, those found in /dev) and drivers
File formats and conventions
Games and screensavers
Miscellaneous
System administration commands and daemons
For example, when you do whatis crontab, you’ll notice that crontab has two man pages (section 1 and section 5). To view section 5 of crontab man page, do the following.
$ whatis crontab
crontab (1) - maintain crontab files for individual users (V3)
crontab (5) - tables for driving cron
$ man 5 crontab
42. tail command examples
Print the last 10 lines of a file by default.
$ tail filename.txt
Print N number of lines from the file named filename.txt
$ tail -n N filename.txt
View the content of the file in real time using tail -f. This is useful to view the log files, that keeps growing. The command can be terminated using CTRL-C.
$ tail -f log-file
More tail examples: 3 Methods To View tail -f output of Multiple Log Files in One Terminal
43. less command examples
less is very efficient while viewing huge log files, as it doesn’t need to load the full file while opening.
$ less huge-log-file.log
One you open a file using less command, following two keys are very helpful.
CTRL+F – forward one window
CTRL+B – backward one window
More less examples: Unix Less Command: 10 Tips for Effective Navigation
44. su command examplesSwitch to a different user account using su command. Super user can switch to any other user without entering their password.
$ su - USERNAME
Execute a single command from a different account name. In the following example, john can execute the ls command as raj username. Once the command is executed, it will come back to john’s account.
[john@dev-server]$ su - raj -c 'ls'
[john@dev-server]$
Login to a specified user account, and execute the specified shell instead of the default shell.
$ su -s 'SHELLNAME' USERNAME
45. mysql command examples
mysql is probably the most widely used open source database on Linux. Even if you don’t run a mysql database on your server, you might end-up using the mysql command ( client ) to connect to a mysql database running on the remote server.
To connect to a remote mysql database. This will prompt for a password.
$ mysql -u root -p -h 192.168.1.2
To connect to a local mysql database.
$ mysql -u root -p
If you want to specify the mysql root password in the command line itself, enter it immediately after -p (without any space).
46. yum command examples
To install apache using yum.
$ yum install httpd
To upgrade apache using yum.
$ yum update httpd
To uninstall/remove apache using yum.
$ yum remove httpd
47. rpm command examples
To install apache using rpm.
# rpm -ivh httpd-2.2.3-22.0.1.el5.i386.rpm
To upgrade apache using rpm.
# rpm -uvh httpd-2.2.3-22.0.1.el5.i386.rpm
To uninstall/remove apache using rpm.
# rpm -ev httpd
More rpm examples: RPM Command: 15 Examples to Install, Uninstall, Upgrade, Query RPM Packages
48. ping command examples
Ping a remote host by sending only 5 packets.
$ ping -c 5 gmail.com
More ping examples: Ping Tutorial: 15 Effective Ping Command Examples
49. date command examples
Set the system date:
# date -s "01/31/2010 23:59:53"
Once you’ve changed the system date, you should syncronize the hardware clock with the system date as shown below.
# hwclock –systohc
# hwclock --systohc –utc
50. wget command examples
The quick and effective method to download software, music, video from internet is using wget command.
$ wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.2.1.tar.gz
Download and store it with a different name.
$ wget -O taglist.zip http://www.vim.org/scripts/download_script.php?src_id=7701
　

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Scanning LUNS on Linux without reboot

#for host in /sys/class/scsi_host/host*; do echo - - - > $host/scan; done

or

echo "- - -" > /sys/class/scsi_host/hostX/scan

X is hba port 0/1/2/3

Note: OS is RHEL

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Add a New Hard Disk VMWARE Without Rebooting Guest

It is possible to add or remove a SCSI device explicitly, or to re-scan an entire SCSI bus without rebooting a running Linux VM guest.

1) Add a New Disk To Vm Guest

• First, you need to add hard disk by visiting vmware hardware settings menu.
  Click on VM > Settings

• Alternatively you can press CTRL + D to bring settings dialog box.

• Click on Add+ to add new hardware to guest:

• Select hardware type Hard disk and click on Next

• Select create a new virtual disk and click on Next

• Set virtual disk type to SCSI and click on Next

• Set maximum disk size as per your requirements and click on Next

• Finally, set file location and click on Finish.

2) Rescan the SCSI Bus to Add a SCSI Device Without rebooting the VM

A rescan can be issued by typing the following command:

echo "- - -" > /sys/class/scsi_host/host#/scan
fdisk -l
tail -f /var/log/message

Replace host# with actual value such as host0. You can find scsi_host value using the following command:

# ls /sys/class/scsi_host

Output:

host0

Now type the following to send a rescan request:

echo "- - -" > /sys/class/scsi_host/host0/scan
fdisk -l
tail -f /var/log/message

3) Format a New Disk

You can create partition using fdisk and format it using mkfs.ext3 command:

# fdisk /dev/sdc
# mkfs.ext3 /dev/sdc3

4) Create a Mount Point And Update /etc/fstab

# mkdir /disk3

Open /etc/fstab file, enter:

# vi /etc/fstab

Append as follows:

/dev/sdc3 /disk3 ext3 defaults 1 2

Save and close the file.

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RPM Command: 15 Examples to Install, Uninstall, Upgrade, Query RPM Packages

RPM Command: 15 Examples to Install, Uninstall, Upgrade, Query RPM Package

RPM command is used for installing, uninstalling, upgrading, querying, listing, and checking RPM packages on your Linux system.

RPM stands for Red Hat Package Manager.

With root privilege, you can use the rpm command with appropriate options to manage the RPM software packages.

In this article, let us review 15 practical examples of rpm command.

Let us take an rpm of Mysql Client and run through all our examples.

1. Installing a RPM package Using rpm -ivh

RPM filename has packagename, version, release and architecture name.

For example, In the MySQL-client-3.23.57-1.i386.rpm file:

• MySQL-client – Package Name
• 3.23.57 – Version
• 1 – Release
• i386 – Architecture

When you install a RPM, it checks whether your system is suitable for the software the RPM package contains, figures out where to install the files located inside the rpm package, installs them on your system, and adds that piece of software into its database of installed RPM packages.

The following rpm command installs Mysql client package.

# rpm -ivh MySQL-client-3.23.57-1.i386.rpm

Preparing... ########################################### [100%]

1:MySQL-client ########################################### [100%]

rpm command and options

• -i : install a package
• -v : verbose
• -h : print hash marks as the package archive is unpacked.

You can also use dpkg on Debian, pkgadd on Solaris, depot on HP-UX to install packages.

2. Query all the RPM Packages using rpm -qa

You can use rpm command to query all the packages installed in your system.

# rpm -qa

cdrecord-2.01-10.7.el5

bluez-libs-3.7-1.1

setarch-2.0-1.1

.

.

• -q query operation
• -a queries all installed packages

To identify whether a particular rpm package is installed on your system, combine rpm and grep command as shown below. Following command checks whether cdrecord package is installed on your system.

# rpm -qa | grep 'cdrecord'

3. Query a Particular RPM Package using rpm -q

The above example lists all currently installed package. After installation of a package to check the installation, you can query a particular package and verify as shown below.

# rpm -q MySQL-client

MySQL-client-3.23.57-1

# rpm -q MySQL

package MySQL is not installed

Note: To query a package, you should specify the exact package name. If the package name is incorrect, then rpm command will report that the package is not installed.

4. Query RPM Packages in a various format using rpm –queryformat

Rpm command provides an option –queryformat, which allows you to give the header tag names, to list the packages. Enclose the header tag with in {}.

# rpm -qa --queryformat '%{name-%{version}-%{release} %{size}\n'

cdrecord-2.01-10.7 12324

bluez-libs-3.7-1.1 5634

setarch-2.0-1.1 235563

.

.

#

5. Which RPM package does a file belong to? – Use rpm -qf

Let us say, you have list of files and you would want to know which package owns all these files. rpm command has options to achieve this.

The following example shows that /usr/bin/mysqlaccess file is part of the MySQL-client-3.23.57-1 rpm.

# rpm -qf /usr/bin/mysqlaccess

MySQL-client-3.23.57-1

• -f : file name

6. Locate documentation of a package that owns file using rpm -qdf

Use the following to know the list of documentations, for a package that owns a file. The following command, gives the location of all the manual pages related to mysql package.

# rpm -qdf /usr/bin/mysqlaccess

/usr/share/man/man1/mysql.1.gz

/usr/share/man/man1/mysqlaccess.1.gz

/usr/share/man/man1/mysqladmin.1.gz

/usr/share/man/man1/mysqldump.1.gz

/usr/share/man/man1/mysqlshow.1.gz

• -d : refers documentation.

7. Information about Installed RPM Package using rpm -qip

rpm command provides a lot of information about the installed pacakges.

# rpm -qip MySQL-client-3.23.57-1.i386.rpm

Name : MySQL-client Relocations: (not relocatable)

Version : 3.23.57 Vendor: MySQL AB

Release : 1 Build Date: Mon 09 Jun 2003 11:08:28 PM CEST

Install Date: (not installed) Build Host: build.mysql.com

Group : Applications/Databases Source RPM: MySQL-3.23.57-1.src.rpm

Size : 5305109 License: GPL / LGPL

Signature : (none)

Packager : Lenz Grimmer

URL : http://www.mysql.com/

Summary : MySQL - Client

Description : This package contains the standard MySQL clients.

• -i : view information about an rpm
• -p : specify a package name

8. List all the Files in a Package using rpm -qlp

To list the content of a RPM package, use the following command, which will list out the files without extracting into the local directory folder.

$ rpm -qlp ovpc-2.1.10.rpm

/usr/bin/mysqlaccess

/usr/bin/mysqldata

/usr/bin/mysqlperm

.

.

/usr/bin/mysqladmin

• q : query the rpm file
• l : list the files in the package
• p : specify the package name

You can also extract files from RPM package using rpm2cpio as we discussed earlier.

9. List the Dependency Packages using rpm -qRP

To view the list of packages on which this package depends,

# rpm -qRp MySQL-client-3.23.57-1.i386.rpm

/bin/sh

/usr/bin/perl

10. Find out the state of files in a package using rpm -qsp

The following command is to find state (installed, replaced or normal) for all the files in a RPM package.

# rpm -qsp MySQL-client-3.23.57-1.i386.rpm

normal /usr/bin/msql2mysql

normal /usr/bin/mysql

normal /usr/bin/mysql_find_rows

normal /usr/bin/mysqlaccess

normal /usr/bin/mysqladmin

normal /usr/bin/mysqlbinlog

normal /usr/bin/mysqlcheck

normal /usr/bin/mysqldump

normal /usr/bin/mysqlimport

normal /usr/bin/mysqlshow

normal /usr/share/man/man1/mysql.1.gz

normal /usr/share/man/man1/mysqlaccess.1.gz

normal /usr/share/man/man1/mysqladmin.1.gz

normal /usr/share/man/man1/mysqldump.1.gz

normal /usr/share/man/man1/mysqlshow.1.gz

11. Verify a Particular RPM Package using rpm -vp

Verifying a package compares information about the installed files in the package with information about the files taken from the package metadata stored in the rpm database. In the following command, -v is for verification and -p option is used to specify a package name to verify.

# rpm -vp MySQL-client-3.23.57-1.i386.rpm

S.5....T c /usr/bin/msql2mysql

S.5....T c /usr/bin/mysql

S.5....T c /usr/bin/mysql_find_rows

S.5....T c /usr/bin/mysqlaccess

The character in the above output denotes the following:

• S file Size differs
• M Mode differs (includes permissions and file type)
• 5 MD5 sum differs
• D Device major/minor number mismatch
• L readlink(2) path mismatch
• U User ownership differs
• G Group ownership differs
• T mTime differs

12. Verify a Package Owning file using rpm -vf

The following command verify the package which owns the given filename.

# rpm -vf /usr/bin/mysqlaccess

S.5....T c /usr/bin/mysql

#

13. Upgrading a RPM Package using rpm -Uvh

Upgrading a package is similar to installing one, but RPM automatically un-installs existing versions of the package before installing the new one. If an old version of the package is not found, the upgrade option will still install it.

# rpm -Uvh MySQL-client-3.23.57-1.i386.rpm

Preparing... ########################################### [100%]

1:MySQL-client ###########################################

14. Uninstalling a RPM Package using rpm -e

To remove an installed rpm package using -e as shown below. After uninstallation, you can query using rpm -qa and verify the uninstallation.

# rpm -ev MySQL-client

15. Verifying all the RPM Packages using rpm -va

The following command verifies all the installed packages.

# rpm -va

S.5....T c /etc/issue

S.5....T c /etc/issue.net

S.5....T c /var/service/imap/ssl/seed

S.5....T c /home/httpd/html/horde/ingo/config/backends.php

.

.

S.5....T c /home/httpd/html/horde/ingo/config/prefs.php

S.5....T c /etc/printcap

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25 Best SSH Commands / Tricks

Friday, November 19, 2010

OpenSSH is a FREE version of the SSH connectivity tools that technical users of the Internet rely on. Users of telnet, rlogin, and ftp may not realize that their password is transmitted across the Internet unencrypted, but it is. OpenSSH encrypts all traffic (including passwords) to effectively eliminate eavesdropping, connection hijacking, and other attacks. Additionally, OpenSSH provides secure tunneling capabilities and several authentication methods, and supports all SSH protocol versions.
SSH is an awesome powerful tool, there are unlimited possibility when it comes to SSH, heres the top Voted SSH commands

1) Copy ssh keys to user@host to enable password-less ssh logins.

ssh-copy-id user@host
To generate the keys use the command ssh-keygen

2) Start a tunnel from some machine’s port 80 to your local post 2001

ssh -N -L2001:localhost:80 somemachine
Now you can acces the website by going to http://localhost:2001/

3) Output your microphone to a remote computer’s speaker

dd if=/dev/dsp | ssh -c arcfour -C username@host dd of=/dev/dsp
This will output the sound from your microphone port to the ssh target computer’s speaker port. The sound quality is very bad, so you will hear a lot of hissing.

4) Compare a remote file with a local file

ssh user@host cat /path/to/remotefile | diff /path/to/localfile -
Useful for checking if there are differences between local and remote files.

5) Mount folder/filesystem through SSH

sshfs name@server:/path/to/folder /path/to/mount/point
Install SSHFS from http://fuse.sourceforge.net/sshfs.html
Will allow you to mount a folder security over a network.

6) SSH connection through host in the middle

ssh -t reachable_host ssh unreachable_host
Unreachable_host is unavailable from local network, but it’s available from reachable_host’s network. This command creates a connection to unreachable_host through “hidden” connection to reachable_host.

7) Copy from host1 to host2, through your host

ssh root@host1 “cd /somedir/tocopy/ && tar -cf – .” | ssh root@host2 “cd /samedir/tocopyto/ && tar -xf -”

Good if only you have access to host1 and host2, but they have no access to your host (so ncat won’t work) and they have no direct access to each other.

8) Run any GUI program remotely

ssh -fX @

The SSH server configuration requires:
X11Forwarding yes # this is default in Debian
And it’s convenient too:
Compression delayed

9) Create a persistent connection to a machine

ssh -MNf @
Create a persistent SSH connection to the host in the background. Combine this with settings in your ~/.ssh/config:
Host host
ControlPath ~/.ssh/master-%r@%h:%p
ControlMaster no
All the SSH connections to the machine will then go through the persisten SSH socket. This is very useful if you are using SSH to synchronize files (using rsync/sftp/cvs/svn) on a regular basis because it won’t create a new socket each time to open an ssh connection.

10) Attach screen over ssh

ssh -t remote_host screen -r
Directly attach a remote screen session (saves a useless parent bash process)

11) Port Knocking!

knock 3000 4000 5000 && ssh -p user@host && knock 5000 4000 3000
Knock on ports to open a port to a service (ssh for example) and knock again to close the port. You have to install knockd.
See example config file below.
[options]
logfile = /var/log/knockd.log
[openSSH]
sequence = 3000,4000,5000
seq_timeout = 5
command = /sbin/iptables -A INPUT -i eth0 -s %IP% -p tcp –dport 22 -j ACCEPT
tcpflags = syn
[closeSSH]
sequence = 5000,4000,3000
seq_timeout = 5
command = /sbin/iptables -D INPUT -i eth0 -s %IP% -p tcp –dport 22 -j ACCEPT
tcpflags = syn

12) Remove a line in a text file. Useful to fix

ssh-keygen -R
In this case it’s better do to use the dedicated tool

13) Run complex remote shell cmds over ssh, without escaping quotes

ssh host -l user $(
Much simpler method. More portable version: ssh host -l user “`cat cmd.txt`”

14) Copy a MySQL Database to a new Server via SSH with one command

mysqldump –add-drop-table –extended-insert –force –log-error=error.log -uUSER -pPASS OLD_DB_NAME | ssh -C user@newhost “mysql -uUSER -pPASS NEW_DB_NAME”
Dumps a MySQL database over a compressed SSH tunnel and uses it as input to mysql – i think that is the fastest and best way to migrate a DB to a new server!

15) Remove a line in a text file. Useful to fix “ssh host key change” warnings

sed -i 8d ~/.ssh/known_hosts

16) Copy your ssh public key to a server from a machine that doesn’t have ssh-copy-id

cat ~/.ssh/id_rsa.pub | ssh user@machine “mkdir ~/.ssh; cat >> ~/.ssh/authorized_keys”
If you use Mac OS X or some other *nix variant that doesn’t come with ssh-copy-id, this one-liner will allow you to add your public key to a remote machine so you can subsequently ssh to that machine without a password.

17) Live ssh network throughput test

yes | pv | ssh $host “cat > /dev/null”
connects to host via ssh and displays the live transfer speed, directing all transferred data to /dev/null
needs pv installed
Debian: ‘apt-get install pv’
Fedora: ‘yum install pv’ (may need the ‘extras’ repository enabled)

18) How to establish a remote Gnu screen session that you can re-connect to

ssh -t user@some.domain.com /usr/bin/screen -xRR
Long before tabbed terminals existed, people have been using Gnu screen to open many shells in a single text terminal. Combined with ssh, it gives you the ability to have many open shells with a single remote connection using the above options. If you detach with “Ctrl-a d” or if the ssh session is accidentally terminated, all processes running in your remote shells remain undisturbed, ready for you to reconnect. Other useful screen commands are “Ctrl-a c” (open new shell) and “Ctrl-a a” (alternate between shells). Read this quick reference for more screen commands: http://aperiodic.net/screen/quick_reference

19) Resume scp of a big file

rsync –partial –progress –rsh=ssh $file_source $user@$host:$destination_file
It can resume a failed secure copy ( usefull when you transfer big files like db dumps through vpn ) using rsync.
It requires rsync installed in both hosts.
rsync –partial –progress –rsh=ssh $file_source $user@$host:$destination_file local -> remote
or
rsync –partial –progress –rsh=ssh $user@$host:$remote_file $destination_file remote -> local

20) Analyze traffic remotely over ssh w/ wireshark

ssh root@server.com ‘tshark -f “port !22″ -w -’ | wireshark -k -i -
This captures traffic on a remote machine with tshark, sends the raw pcap data over the ssh link, and displays it in wireshark. Hitting ctrl+C will stop the capture and unfortunately close your wireshark window. This can be worked-around by passing -c # to tshark to only capture a certain # of packets, or redirecting the data through a named pipe rather than piping directly from ssh to wireshark. I recommend filtering as much as you can in the tshark command to conserve bandwidth. tshark can be replaced with tcpdump thusly:
ssh root@example.com tcpdump -w – ‘port !22′ | wireshark -k -i -

21) Have an ssh session open forever

autossh -M50000 -t server.example.com ‘screen -raAd mysession’
Open a ssh session opened forever, great on laptops losing Internet connectivity when switching WIFI spots.

22) Harder, Faster, Stronger SSH clients

ssh -4 -C -c blowfish-cbc
We force IPv4, compress the stream, specify the cypher stream to be Blowfish. I suppose you could use aes256-ctr as well for cypher spec. I’m of course leaving out things like master control sessions and such as that may not be available on your shell although that would speed things up as well.

23) Throttle bandwidth with cstream

tar -cj /backup | cstream -t 777k | ssh host ‘tar -xj -C /backup’
this bzips a folder and transfers it over the network to “host” at 777k bit/s.
cstream can do a lot more, have a look http://www.cons.org/cracauer/cstream.html#usage
for example:
echo w00t, i’m 733+ | cstream -b1 -t2

24) Transfer SSH public key to another machine in one step

ssh-keygen; ssh-copy-id user@host; ssh user@host
This command sequence allows simple setup of (gasp!) password-less SSH logins. Be careful, as if you already have an SSH keypair in your ~/.ssh directory on the local machine, there is a possibility ssh-keygen may overwrite them. ssh-copy-id copies the public key to the remote host and appends it to the remote account’s ~/.ssh/authorized_keys file. When trying ssh, if you used no passphrase for your key, the remote shell appears soon after invoking ssh user@host.

25) Copy stdin to your X11 buffer

ssh user@host cat /path/to/some/file | xclip
Have you ever had to scp a file to your work machine in order to copy its contents to a mail? xclip can help you with that. It copies its stdin to the X11 buffer, so all you have to do is middle-click to paste the content of that looong file :)
Have Fun
courtesy :http://blog.urfix.com

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