Month: December 2017

Fab 5 Linux Tips: logins

This is the first Fab 5 Linux tips of the series. I’ll post 5 tools, commands, hacks, configs, etc that you can use for administering your Linux Systems.

Here are the Fab 5 quick tips on keeping up with users who log into your servers.

  1. lastlog
  2. w
  3. who
  4. lslogins
  5. last

lastlog – reports the most recent login of all users or of a given user

# lastlog

Lastlog alone prints out the last login of all the users on the system. Accounts that have never been used and service account that don’t log in, indicate that they’ve never logged in.

-u print out the last login of a particular user. It lists the pseudo terminal used, IP address the login came from, as well as the date and time.

# lastlog -u username

 

W shows who is logged on and what processes they’re running.

# w

W alone shows everyone who’s logged in right now.

# w username

displays a specific users login and what processes they’re currently running.

Who  show who is logged on. It’s slightly different than w, in that it just prints who’s logged in, what terminal and from what IP address. It doesn’t show what processes they’re running. Either one would work, if you’re just looking to see who’s logged in at the moment. Who as a few more options that give it a bit more functionality

# who -b

this give the last boot time of the server. Similar to #uptime, w tells you the time and date of the last boot, uptime gives you the current time and how long the server has been up and running.

#who -q

If you’re only looking to see just how many users are logged in at the moment, and not much else, this will do the trick

Lslogins display information about known users on the system.

#lslogins

Prints a list of logins (system and user)

#lslogins -fu

Prints out the failed logins of regular users

There is also a command called faillog that does the same thing, but it doesn’t appear to be installed on my RHEL 6.9 server and on Ubuntu 16.04, the information is pretty meaningless out of the box. YMMV.

Last and LastB show a listing of last logged in users.

#last -aF | head

Displays the last logins, with login and logout times.

lastb is the same as last, except that by default it shows a log of the /var/log/btmp file, which contains all the bad login attempts. Here you get a peek at all the attempts of people trying to log into your system.

 

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Connect Drobo B800i to CentOS 7 via iSCSI

Drobo Dashboard
CentOS 7.4.1708 Kernel 3.10.0.-693.11.1.el7.x64_86
Drobo B800i Firmware 2.0.6

The Drobo and the host computer must be on the same subnet in order for this to work. (See Drobo Online User Guide)

Preparation

After configuring the device’s IP and other settings via USB from my Windows desktop using Drobo Dashboard, I created a 1TB, unformatted volume.

Format Dialog box

Information you’ll need to connect to machine:

  • Target Name
  • IP address of device

I did not enable CHAP, but it can be easily configured on the machine. I also disabled SELinux on this test box.

**note** your Drobo must be on the same subnet as your server.

I installed the iscsi initiator utilities.

$ sudo yum install -y scsi-target-utils

Configure the server

On the CentOS server, install the iscsi package

# yum -y install iscsi-initiator-utils

List out the /proc/partitions file to see the devices that you have currently. Once you login to the iSCSI volume, a new one will appear and that’s the one we’ll format.

# cat /proc/partitions

Add the target name to /etc/iscsi/initiatorname.iscsi file, save and exit.

#  vim  /etc/iscsi/initiatorname.iscsi
InitiatorName=iqn.2005-06.com.drobo:b800i.tdb1504b0092.id1

iscsiadm discovery command

Use the iscsiadm command to discover the target.

# iscsiadm -m discovery -t  sendtargets -p 10.253.53.25

Once your volumes are discovered, you can login to them

# iscsiadm -m node -T iqn.2005-06.com.drobo:b800i.tdb1504b0092.id1 -p 10.253.52.25 --login

List out the /proc/partitions file to see the new disk.

# cat /proc/partition

 

Command to display partitions

command to login the iscsi target

If the login is successful, run the dmesg | tail command to see if the kernel sees the logical blocks.

# dmesg | tail

Time to partition the device. 

Run the parted command against the device to create a new disk label. Run It again to create the primary partition

# parted --script  /dev/sdb mklabel msdos
# parted --script  /dev/sdb mklabel primary 0% 100%

If by chance you get an error that reads:

Warning: The resulting partition is not properly aligned for best performance

Read this blog post and make the adjustments. 2048s is a good choice for the starting sector.

Check the disk alignment

# parted /dev/sdb align-check optimal 1

If it returns 1 aligned, you’re good to go.

Format your disk

# mkfs.ext3 /dev/sdb1

*note* I’d read that this Drobo didn’t support ext4 and after formatting the volume, I found that to be false.

Mount your disk

# mount /dev/sdb1 /drobo

Confirm that you can write to it

# touch /drobo/testfile

Check the  file system disk space usage.

# df -hT

*Notes & Caveats*

  • All volumes on the Drobo were ‘visible’ in file manager. If you have multiple volumes on the target, you’ll see them all in GUI file manager.
  • They have a different name after each reboot /dev/sdb1 or /dev/sdc1,
  • Adding it to /fstab didn’t matter, since the name changed after every reboot.
  • They show as ‘on my computer’ and when I click on the drive, it mounts to /run/media/username/some-really-long-number-and-series-of-letters. The media directory isn’t even present  under the/ run director after a reboot. It only appears once I click on the disk in the file manager.
  • I’ve read a few blogs where it’s better to present the Drobo as 1 large volume to a Linux system.
  • I formatted it as ext3 just fine. I’d read in another blog that it doesn’t support ext4. I didn’t find a definitive answer in the online guide to confirm or deny it until I saw the above mentioned alert in the dashboard.

You can set the target to login and mount at boot by editing the /etc/fstab and by using the iscsiadm command to set it to automatic.

 

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Leveling up skills with Linux Academy

My stand up desk with the Linux Academy Penguin

I haven’t been blogging much, I’ve been busy learning.

I got a subscription to Linux Academy and for the past month, I’ve been immersed in retooling for a skill switch into DevOps. I’ve been using Linux for years, but my goal is not to have a cursory understanding of the OS, but to be as comfortable in it as I am in Windows. I’ve gotten a few successful completions on a few courses on Linux Academy under my belt. I’m currently in the Linux, Cloud, and Ruby Coding learning path which consists of:

  • Linux Essentials Certification (done)
  • CompTIA Cloud Essentials Certification (in progress)
  • AWS Certified Solutions Architect – Associate
  • OpenStack Essentials
  • Nginx And The LEMP Stack
  • Introduction To Ruby Programming Language On Linux

Linux Academy Completion Certificate- Linux Essentials Linux Academy Completion Certificate- DevOps Essentials

I’ll sit for the LPI Linux Essentials exam this month and move on to the AWS Certified Solutions Architect-Associate exam after that.

In the meantime, I’m writing 2 blog series that will highlight some of the tools, commands, packages that I come across in my studies. Today’s 10 will highlight 10 commands, tips, tricks, etc. The other, Fab 5 will cover 5 quick hitters about Linux.

Stay tuned for more posts about my DevOps journey.

 

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Today’s 10 Commands: Command-Line Navigation

Introducing 2 new blog series: Today’s 10 & Fab 5

This is the first of many blog posts about commands, utilities and tips I’m either learning for the first time or re-familiarizing myself with. This series is called Today’s 10, 10 commands, tips, tricks, etc. I will have another series called Fab 5 for the quick hitters that I come across.

Command-Line navigation:

We all have done it, backspaced and back and forth, arrow up and down the command line. Trying to correct errors, change things after an erroneous tab completions and make changes to command after we’ve pulled them up in our history.

Here are 10 commands that will have you zipping around the shell prompt in no time.

  1. Alt+b – will move your cursor back one word at a time to start of the word.
  2. Alt+f – will move your cursor forward one word at a time to the end of the word.
  3. Alt+d – will delete to the end of that misspelled word starting at the cursor.
  4. Ctrl+e – move your cursor at the end of the line.
  5. Ctrl+ a – move your cursor to the beginning of the line.
  6. Ctrl+l – clear your screen (clear also will do the trick).
  7. Ctrl +w – deletes from the cursor to the beginning of the word or path.
  8. Ctrl+c – clears the entire line. (yes, THAT ctrl+c) and takes to to a blank command prompt.
  9. Ctrl+f – move cursor forward one character at a time, like the right arrow key.
  10. Ctrl+b – move cursor backward one character at a time, like the left arrow key.

Watch your command-line navigation improve as you use these keystrokes more and more. There are many, many more, but these are the 10 that I use the most.

What are some of your favorite command-line shortcuts?

 

 

 

 

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404 error when downloading .iso file on IIS

I’m running IIS8 and I have a site where I can wget and download isos easily.

I got a 404 error when trying to download an iso:

Image of a 404 error from IIS

You must add the correct MIME type for the file you’re trying to download.

From IIS Manager, go to Sites > YOUR_SITE> and in the features view, double-click MIME Types.

Under actions, click Add.

Enter the file extension iso and the MIME type application/octetstream

Add MIME type dialog box

Click OK and retry your download.

iso downloading

 

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