Category: Operating System

win retired 2

Say Goodbye to Windows 7 and Windows Server 2008 (R2)

Windows 2008 was born on February 2018 and Microsoft released Windows 2008 R2 on October 2009. I think, Windows 2008 R2 was one of most popular Windows servers in history.

Now, Windows 7, Windows 2008 and Windows 2008 R2 are old men. We have to say goodbye to these guys in this year and next year.

Linux Distribution 1

How to Secure SSH Connection on Linux

Why We Should Mitigate SSH Based Attack SSH (Secure Shell) is a most popular remote protocol. SSH allows remote login and execute commands. That providing secure way to login and run commands on remote systems in unsecured networks. Telnet replace with SSH cause of offering more security. But SSH has some weaknesses, in order to reducing SSH based attack, those weaknesses can be mitigated. There is some hardening tips, the tips turn your SSH server into a rock solid communication daemon. Best SSH Hardening Tips In the next minutes, we’ll review 15 solutions from best SSH hardening tips. Each hardening tip will a shield against SSH based attacks. Most of the tips are SSH configurations, some of those tips are different on Linux distributions, so please check the configurations on your distribution documents as well. Also Windows 10 and Windows 2019 have OpenSSH server by adding Win32-OpenSSH to Windows, so read Microsoft documents as well. You must restart SSH server daemon after applying configurations. 1. Custom SSH Port SSH server listening on port 22 by default, so attackers trying to attack your server on port 22. Changing SSH port to another port is a solution to reduce attacks. In order to change...

ancient 1

NTP Software Implementations Comparison

This post is about NTP Software implementations actually, but I have to write some words about NTP. NTP is an angle for financial applications, actually some of services such as banking services are very depended to clock synchronizations protocols. NTP is an ancient thing, it is more than 30 years old and even older than Windows 7 and Windows XP.

Microsoft Windows Insight 0

[Review]: Introducing Windows Server System Insights

As an IT admin, one of the responsibilities you have is to ensure systems continue to run smoothly. That is true for a number of activities and components, such as monitoring if a disk is going to run out of space, determining how much memory and processing a Hyper-V host is consuming so you can plan for new VMs, and many other examples.

Linux Kernel Patching 0

[Review]: What’s kernel Live Patching?

Dynamic Software Updating (DSU) Dynamic Software Updating (DSU) is a field of research pertaining to upgrading programs while they are running. DSU is not currently widely used in industry. However, researchers have developed a wide variety of systems and techniques for implementing DSU. These systems are commonly tested on real-world programs. Current operating systems and programming languages are typically not designed with DSU in mind. As such, DSU implementations commonly either utilize existing tools, or implement specialty compilers. These compilers preserve the semantics of the original program, but instrument either the source code or object code to produce a dynamically update-able program. Researchers compare DSU-capable variants of programs to the original program to assess safety and performance overhead. Software Hot-Swapping Hot swapping can also refer to the ability to alter the running code of a program without needing to interrupt its execution. Interactive programming is a programming paradigm that makes extensive use of hot swapping, so the programming activity becomes part of the program flow itself. Only a few programming languages support hot swapping natively, including Pike, Lisp, Erlang, Smalltalk, Visual Basic 6 (Not VB.net), Java and most recently Elm and Elixir. Microsoft Visual Studio supports a kind of hot swapping called Edit and Continue, which is supported by C#, VB.NET and C/C++ when running under a debugger. Hot swapping is the central method in live coding,...

Windows Admin Center - Server Manager 1

[Review]: Windows Admin Center (Project Honolulu)

Windows Admin Center (Formerly Project Honolulu) is a new browser based management tool. Windows Admin Center the evolution of traditional in-box server management tools for situations where you might have used Remote Desktop (RDP) to connect to a server for troubleshooting or configuration. It’s not intended to replace other existing Microsoft management solutions.

Packet Loss 1

[Review]: Packet Drop vs Packet Loss – Linux

Actually, Packet Loss occurs when one or more packet can’t reach their destination because of some issue such as link congestion, TCP can detect packet loss and send the packet again (During packet recovery process) but packet loss has impact on users, who are using streaming media application and actually all application that using unreliable protocols such as UDP.

Packet Drop is typically discarding packets on different layers after processing packets and packet drop is one of reasons of data loss in some conditions.

Access to Shell via VI or VIM 1

[How To]: Access to Shell via VI or VIM Editor

Shell Access via VI or VIM Why do you need to access shell via VI or VIM? A: sometimes, you have to copy result of a commands and paste those results to editor. For example, you are configuring SCSI devices as DM-Multipath devices, you have to run some commands like “multipath -l” for see “WWID” of specific device and add the “WWID” to “multipath.conf”. As simple solution, you can run another ssh session and run the command on this session, then copy and paste the result. But I think, there is another good way to do it. You can access to shell via VI or VIM editor and do your job! But how to? How to Access Shell via VI or VIM? Run VI or VIM command to open the editors and start to edit your file. For accessing to shell, you must run the below command within VI or VIM: :shell Or this command: :sh Then you will access to shell and the editor is still open. The shell is opened for your temporary, so you must have access to editor again. Press Ctrl+D or type “exit” and hit Enter for return back to the editor.

Linux Distribution 0

[How To]: Linux tac Command – Usage and Examples

Linux tac Command tac command practically is reverse version of cat command. It means, any result in cat command will be reversed by tac command. tac is lesser known and less used command in Linux but I want to show you the command usage and some examples. Usage and Examples tac command has few options same as cat command, we’ll review some of its options at the below. Example 1 Comparison cat and tac outputs. In this example, we have a file with the below content: [root@localhost ~]# cat sample1.txt This is first line. This is second line. This is third line. This is fourth line. Now, print the file’s content by tac: [root@localhost ~]# tac sample1.txt This is fourth line. This is third line. This is second line. This is first line. Example 2 Both tac and cat commands has separator option which one of the most important options and the command is represented by the -s switch, which separates the contents of the file based on a string or a keyword from the file. [root@localhost ~]# cat sample1.txt —1— 1 2 3 —2 A B C —3– a b c [root@localhost ~]# tac –before –regex –separator=^—[0-9]+-*$ sample1.txt —3–...

Linux Cat Command - Create New File 0

[How To]: Linux Cat Command – Usage and Examples

Linux Cat Command Cat or “concatenate files and print on the standard output” is a Linux command to print file content on the standard output like screen. This is one of most popular Linux commands. I think that every Linux administrator has executed the below command at least one time 😉 : # cat /var/log/messages So this is actually very useful and popular command. Usage and Examples Cat command has few options but has lot of usages. Show file content: If Cat command run without options, it will shows you the content of the file or files. Show multiple files content: You can view content of multiple files by entering more than one file name in command line, see the below example: Create New File: You be able to create new file by Cat command. Run the below command and then enter some strings and when it’s finished hit Enter, if you are end of a line and then Ctrl+D for save the new file. Please consider that existing files will be overwrite by run same command.   Join Multiple Files: Joining multiple files to a file is possible by Cat command. Here is an example: # cat file1.txt file2.txt file3.txt > all-files.txt...

kernel: WARNING: at fs/sysfs/dir.c:536 sysfs_add_one+0xbb/0xe0 – Oracle Enterprise Linux 0

kernel: WARNING: at fs/sysfs/dir.c:536 sysfs_add_one+0xbb/0xe0 – Oracle Enterprise Linux

Most of modern servers hardware are using UEFI instead of legacy BIOS and modern OS has dedicated partition to stores boot and EFI values. Some times, the partition gets full or OS generate the below log: kernel: WARNING: at fs/sysfs/dir.c:536 sysfs_add_one+0xbb/0xe0 Kernel includes a CONFIG_EFI_VARS_PSTORE feature, and a feature that dumps kernel message log (= the “dmesg” command output) into UEFI variables for persistent storage if the system is crashing (or even if the system is working normally, depending on the options chosen). The cause of the warning is duplicate dump file in EFI partition and OS is trying to write values on same file. There is a simple solution, remove old dump file! I hope this article help you to find out root cause of the warning and resolve that. Here is the complete log on our virtual machine: kernel: WARNING: at lib/kobject.c:196 kobject_add_internal+0x205/0x260() kernel: Hardware name: VMware7,1 kernel: kobject_add_internal failed for dump-type2-0-0-1493749396-cfc8fc79-be2e-4ddc-97f0-9f98bfe298a0 with -EEXIST, don’t try to register things with the same name in the same directory. kernel: Modules linked in: vmw_vsock_vmci_transport vsock oracleasm autofs4 ipv6 vfat fat uinput vmw_balloon coretemp crc32c_intel ghash_clmulni_intel microcode pcspkr sg ixgbe hwmon dca vmw_vmci i2c_piix4 shpchp ext4 jbd2 mbcache dm_round_robin scsi_dh_emc sd_mod...

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Find HBA Firmware Version in Linux – Easy Way

You need to know, what is version of your HBA firmware to upgrade it or install compatible driver version. There is many ways to find firmware version but I want to share easier way. Just logon to your Linux machine with Sudo user and run the below command: cat /sys/class/fc_host/host*/symbolic_name

RedHat 0

Change Network Device Name Permanently – RedHat

Device Naming Device name management is handled by udev system. When Linux kernel discovers a new device (e.g., a network interface card) added to the system, it notifies udev daemon of the device event. The udev daemon will then match various device attributes against a set of rules to identify the device, name it, and store its information in udev database. In case of network devices, udev relies on MAC addresses to assign persistent names to the devices. The MAC address based naming rules are stored in “/etc/udev/rules.d/70-persistent-net.rules”.