KernelTalks implemented few blog enhancements for better SEO and reader engagement. Addition of SSL, AMP & browser push notifications to blog
SSL, AMP and notification! Blog enhancements.
A few months ago we did blog enhancement for better speed and cleaner look by adding premium theme built on Genesis framework and CDN support for lightning-fast page loads. This month we are adding a few more enhancements and features to blog which helps us build better SEO and people engagement.
SSL support
We have added SSL support to our blog. Now kerneltalks.com loads over https protocol (more secured). Information sends to us will be secured over the internet. Since many of you already know, SSL is one more factor to rank pages in search by Google. This implementation will help us building good ranks in Google search results and building more organic traffic.
Blog is now AMP ready
Google in recent times declared AMP (Accelerated mobile pages) as one of the ranking factors. AMp ensures loading pages on mobile devices almost in no time. This is done via removing all scripts, styling, and very limited special HTML tagging of page. KernelTalks now AMP ready! Now our posts are listed in google results with AMP lightning icon!
AMP pages
You can even view the amp version of kerneltalks by appending /amp to any of our URLs in the browser. We are more closer to the audience with lower bandwidth and loading our pages lightning fast even on mobile devices. If you want to customize and stylish your AMP pages try plugin named AMP for WP. It has all customization you need along with the option to configure AdSense ads.
Browser push notifications
One more reader engagement option enabled for kerneltalks. We have started browser push notifications (supports Chrome, Firefox, Safari) which will notify you about our new articles whenever you open up your browser. You can opt into these notifications by clicking allow in a popup window when you now visit kerneltalks.com. We are using Onesignal push utility for this. This is the best free service allowing unlimited subscribers so you can go for it if you are looking for one for your blog.
That’s all for now! Keep blogging! Let us know your feedback about our blog in the comments.
Learn how to create, view, and remove command alias in Linux or Unix. Useful to shorten long commands or imposing switches to commands.
Command alias
Command alias in Linux is another (mostly short) version of frequently used command (or command with arguments). It is meant for lessening keystrokes to type long commands and making it fast, easy, and accurate to work in shell. On the other hand, if you want users to use some commands with preferred switch always, you can create an alias of it. For example, rm command can be aliased to rm -i so that it will be always interactive asking the user to confirm his remove operation.
In this article we will see how to create command alias, how to remove the alias, and how to list alias.
How to create alias
Creating alias is an easy job. You have to specify alias and command to alias like below :
# alias ls='ls -lrt'
Here in this example, we are aliasing command ls to ls -lrt so that whenever we type ls command it will long list, reverse order with a timestamp. Saving out time to write long command with arguments. See how differently ls works before and after alias in the below output.
# ls
apache httpd-2.4.25 httpd-2.4.25.tar letsencrypt lolcat-master master.zip shti
# alias ls='ls -lrt'
# ls
total 38504
-rw-r--r--. 1 root root 39198720 Dec 19 12:29 httpd-2.4.25.tar
drwxr-xr-x. 5 root root 4096 Dec 26 07:48 lolcat-master
-rw-r--r--. 1 root root 205876 Mar 22 02:21 master.zip
drwxr-xr-x. 2 root root 4096 Mar 29 08:15 apache
drwxr-xr-x. 12 501 games 4096 Mar 29 08:42 httpd-2.4.25
drwxr-xr-x. 14 root root 4096 Apr 3 15:07 letsencrypt
drwxr-xr-x. 2 root root 4096 May 16 01:29 shti
Make a note that this alias will be available in the current shell only. If you want to make it permanent over reboots, spawns over other users and shells then you need to define it in /etc/profile or respective shell profiles of the individual users. Defining it in profiles is the same syntax, just add the above command in a profile file and it will works once the profile is sourced.
List alias in current shell
To view and list all aliases currently active in your shell, just type command alias without any argument.
# alias
alias cp='cp -i'
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'
alias ls='ls -lart'
alias mv='mv -i'
alias rm='rm -i'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
In the above output you can see all commands on the left of = and values they are aliased for in the right section. These aliases are defined on /etc/profile or user profiles or shell profiles or defined in the shell with alias command.
How to delete alias
In case you want to remove or delete alias you defined, you need to use unalias command. This command takes your alias command (left portion of = in the above listing) as an argument.
# unalias ls
# alias
alias cp='cp -i'
alias l.='ls -d .* --color=auto'
alias ll='ls -l --color=auto'
alias mv='mv -i'
alias rm='rm -i'
alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'
Observe in above output after un-aliasing ls, its alias to ls -lart vanishes from alias listing. Keep in mind that this un-alias is limited to the current shell only. If you want to permanently un-alias command then you need to remove it from the profile file where you have defined it and re-source that profile.
Fun in terminal using alias
By now you know how alias works, you can play around to have some fun in the terminal. You can alias funny statements to commonly used commands. For example aliasing ls to cmatrix command to run matrix green falling code in terminal and stun user!
# alias ls=' echo I love kerneltalks.com :D'
# ls
I love kerneltalks.com :D
As you know how it can turn evil if it gets into the wrong hands! So be extra cautious when defining an alias for destructive commands.
Learn the configuration of iptables policies in Linux. Know how to add, delete, save Linux native firewall rules in iptables.
Configuring iptables policies in Linux
In our last article about iptables, we have seen the basics of iptables, iptables chains, and chain policy strategy. In this article we will walk through how to define iptables policies.
Defining iptables policies means allowing or blocking connections based on their direction of travel (incoming, outgoing or forward), IP address, range of IP addresses, and ports. Rules are scanned in order for all connections until iptables gets a match. Hence you need to decide and accordingly define rule numerically so that it gets match first or later than other rules.
In newer versions like RHEL7, the firewall is still powered by iptables only the management part is being handled by a new daemon called firewalld.
iptables is the command you need to use to define policies. With below switches –
-A: To append rule in an existing chain
-s: Source
-p: Protocol
–dport: service port
-j : action to be taken
Lets start with examples with commands.
Block/Allow single IP address
To block or allow a single IP address follow below command where we are adding a rule -A to input chain (INPUT) for blocking (-j REJECT).
In the above command we are blocking incoming connections from IP 172.31.1.122. If you see the output of rules listing, you can see our rule is defined properly in iptables. Since we didn’t mention protocol, all protocols are rejected in the rule.
Here chain can be any of the three: input (incoming connection), output (outgoing connection), or forward (forwarding connection). Also, action can be accepted, reject, or drop.
Block/Allow single IP address range
Same as single IP address, whole address range can be defined in rule too. The above command can be used only instead of IP address you need to define range there.
I have shown two different notation types to define the IP address range/subnet. But if you observe while displaying rules iptables shows you in /X notation only.
Again action and chain can be any of the three of their types as explained in the previous part.
Block/Allow specific port
Now, if you want to allow/block specific port then you need to specify protocol and port as shown below :
Here in this example we blocked the telnet port using TCP protocol from specified source IP. You can choose the chain and action of your choice depending on which rule you want to configure.
Saving iptables policies
All the configuration done above is not permanent and will be washed away when iptable services restarted or server reboots. To make all these configured rules permanent you need to write these rules. This can be done by supplying save argument to iptables service (not command!)
# /sbin/service iptables save
iptables: Saving firewall rules to /etc/sysconfig/iptables:[ OK ]
You can also use iptables-save command.
If you open up /etc/sysconfig/iptables file you will see all your rules saved there.
# cat /etc/sysconfig/iptables
# Generated by iptables-save v1.4.7 on Tue Jun 13 01:06:01 2017
*filter
:INPUT ACCEPT [32:2576]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [48:6358]
-A INPUT -s 172.31.1.122/32 -j REJECT --reject-with icmp-port-unreachable
-A INPUT -s 172.31.0.0/22 -j REJECT --reject-with icmp-port-unreachable
-A INPUT -s 172.31.0.0/23 -j REJECT --reject-with icmp-port-unreachable
-A INPUT -s 172.31.1.122/32 -p tcp -m tcp --dport 23 -j DROP
COMMIT
# Completed on Tue Jun 13 01:06:01 2017
Deleting rule in iptables
We have seen how to add a rule, how to delete the existing rules. You can use the same commands used above only change is to add -D switch instead of -A!
# iptables -D INPUT -s 172.31.1.122 -j REJECT
The above command will remove the very first rule we added in iptables in this post.
Also, if you haven’t saved your iptables you can flush all currently configured rules by using -F.
Beginner’s tutorial to understand iptables – Linux firewall. This article explains about iptable basics, different types of chains, and chain policy defining strategy.
iptables – Linux firewall
Linux firewall: iptables! plays a very important role in securing your Linux system. System hardening or locking down cannot be completed without configuring iptables. Here we are discussing the basics of iptables. This article can be referred to by beginners as an iptables guide. In this article we will walkthrough :
What is iptables
iptables chains
Chain policy defining strategy
We discussed how to set iptables rules, how to save iptables settings in this article. Let’s start with iptables basics.
What is iptables
iptables is a Linux native firewall and almost comes pre-installed with all distributions. If by any chance its not on your system you can install an iptables package to get it. As its a firewall, it has got policies termed as ‘chain policies’ which are used to determine whether to allow or block incoming or outgoing connection to or from Linux machine. Different chains used to control the different types of connections defined by its travel direction and policies are defined on each chain type.
In newer versions like RHEL7, the firewall is still powered by iptables only the management part is being handled by a new daemon called firewalld.
As there are policies you can define, one default policy also exists for all chains. If the connection in question does not match with any of the defined policy chains then iptable applies default policy action to that connection. By default (generally) ALLOW rule is configured in defaults under iptables.
iptable chains
As we saw earlier iptables rely on chains to determine the action to be taken in connection, let’s understand what are chains. Chains are connection types defined by their travel direction/behavior. There are three types of chains: Input, Output, Forward.
Input chain :
This chain is used to control incoming connections to the Linux machine. For example, if the user tries to connect the server via ssh (port 22) then the input chain will be checked for IP or user and port if those are allowed. If yes then only the user will be connected to the server otherwise not.
Output chain :
Yes, this chain controls outgoing connections from the Linux machine. If any application or user tries to connect to outside server/IP then the output chain decides if the app/user can connect to destination IP/port or not.
Both chains are stateful. Meaning only said the connection is allowed and a response is not. Means you have to exclusively define input and output chain if your connection needs both way communication (from source to destination and back)
Forward chain :
In most of the systems, it’s not used. If your system is being used as a pass-through or for natting or for forwarding traffic then only this chain is used. When connections/packets are to be forwarded to next hop then this chain is used.
You can view the status of all these chains using the command :
# iptables -L -v
Chain INPUT (policy ACCEPT 8928 packets, 13M bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 2201 packets, 677K bytes)
pkts bytes target prot opt in out source destination
In above output, you can see all three chains details, how many packets were transferred, how much data transferred and default action policy.
Chain policy defining strategy
There are three policies can be defined for chains.
ACCEPT: Allow connection
REJECT: Block connection and send back error message informing source that destination blocked it
DROP: Block connection only (behave like connection never questioned). The source is unaware of being blocked at the destination.
By default, all chains configured with ACCEPT policy for all connections. When configuring policies manually you have to pick either way from below two :
Configure default as REJECT/DROP and exclusively configure each chain and its policy of ALLOW for required IP/subnet/ports.
Configure default as ACCEPT and exclusively configure each chain and its policy of REJECT for required IP/subnet/ports.
You will go with number two unless your system has highly sensitive, important data and should be locked out of the outer world. Obviously, its environment criticality and number of IP/subnet/ports to be allowed/denied makes it easier to select a strategy.
In next article we discussed how to define these chain policies in detail.
Learn 5 different ways to check swap space utilization on Linux server using free, swapon, /proc/swaps, top and vmstat/sar commands.
Check swap on linux
This is a short, handy post explaining how to check swap space on the Linux server with different commands. We already discussed about swap in few of old posts listed below :
In this post we will be seeing 5 ways to check swap space and utilization in the Linux server.
Using free command
Most of the users know this command. Using free you can check memory and swap utilization on the server in a few lines. By default, without any switch it shows numbers in kilobytes.
In the above output you can see the last row shows swap values, total, used, and free! Here swap value you see is a total of all swap devices on the system. You cant get device wise separated swap summery with this command. To view device wise summery you can use the next commands.
Using swapon command
Generally, swapon command is used to turn on swap on partition, logical volume or file. But using -s switch (summery) you can get current swap information.
# swapon -s
Filename Type Size Used Priority
/myswapfile file 8188 0 -1
This command provides you output size in kilobytes. It also shows you device wise swap so that you can see device name (partition, logical volume or file), its type and how much swap it contributing to the system.
Using /proc/swaps file
Another way is to view the content of the process file /proc/swaps for the current swap config. This outputs the same content as we saw in previous command swapon -s. In fact swapon reads this file to print a summary.
# cat /proc/swaps
Filename Type Size Used Priority
/myswapfile file 8188 0 -1
Output explanation is already covered above in swapon -s.
Using top command
Another popular well-known monitoring tool top can be used to view swap information. In the top output you can see the header section includes swap details.
Values in a row for the swap are in kilobytes. This information is also available in other advanced iterations or top alike tools like atop, htop or glance.
Using vmstat or sar command
In vmstat you can see the utilization of swap like swap in and swap out but not the devices or total values of swap like we saw in previous commands.
# vmstat
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 0 821064 14564 76500 0 0 91 17 25 31 0 1 98 0 0
It’s more of swap monitoring. You can generate reports for certain iteration with particular time intervals like sar reporting.
# sar -S 2 3
Linux 2.6.39-200.24.1.el6uek.x86_64 (testsrv2) 12/21/2016 _x86_64_ (4 CPU)
01:01:45 AM kbswpfree kbswpused %swpused kbswpcad %swpcad
01:01:47 AM 8388604 0 0.00 0 0.00
01:01:49 AM 8388604 0 0.00 0 0.00
01:01:51 AM 8388604 0 0.00 0 0.00
Average: 8388604 0 0.00 0 0.00
These are 5 ways to get swap information out of your system. If you know any other methods do let us know in comments!
Learn how to add swap using LVM, swap file, and parted disk management. Also, learn how to extend existing swap partition on Linux server
Add swap in Linux
We have already seen what is swap in article difference between tmpfs and swap. In this how-to article we will be checking out how to add swap using LVM disk, how to extend swap, how to add swap using file, and how to add swap using the parted disk.
How to add swap in Linux using LVM
If you have LVM disk partitioning in your server then you can go ahead with this method. You need a dedicated logical partition that can be used as a swap. So steps involved are :
Create a new logical volume of the desired size using lvcreate
I gave you the below outputs for reference. In lvcreate command -L should be followed by size in MB.
# lvcreate -L 500 -n myswaplv vg01
Logical volume "myswaplv" created.
# mkswap /dev/vg01/myswaplv
mkswap: /dev/vg01/myswaplv: warning: don't erase bootbits sectors
on whole disk. Use -f to force.
Setting up swapspace version 1, size = 511996 KiB
no label, UUID=5339bdde-c734-48d3-94fd-0ab50ef38b4e
# swapon -va
# free
total used free shared buffers cached
Mem: 1018308 186344 831964 152 14616 65784
-/+ buffers/cache: 105944 912364
Swap: 511996 0 511996
# cat /proc/swaps
Filename Type Size Used Priority
/dev/dm-0 partition 511996 0 -1
Warning in mkswap you (may) see is a precautionary warning to make sure you are not using full disk if you meant to use the only partition of it and destroy boot sectors!
You can see free and /proc/swaps shows 500MB of swap which we created. Sometimes if you don’t get your swap activated just by using swapon then try a reboot and it should work. But before reboot makes an entry described hereafter. To make this permanent i.e. at reboot setting lvol to swap again, add below entry in /etc/fstab file.
/dev/vg01/myswaplv swap swap defaults 0 0
How to extend swap
In case you want to extend the existing swap rather than creating a new volume for it then you can still do it on the fly (without reboot). Make sure your swap is not being used and turn it off on volume which you want to extend. Process is as follows –
Turn off swap on volume using swapoff
Extend lvol using lvresize
Define it again as a swap using mkswap
Turn on swap on volume using swapon
Refer below outputs on how commands work and their arguments. Here I extended 500MB swap to 600MB.
# swapoff -v /dev/vg01/myswaplv
swapoff on /dev/vg01/myswaplv
# cat /proc/swaps
Filename Type Size Used Priority
# lvresize /dev/vg01/myswaplv -L 600M
Size of logical volume vg01/myswaplv changed from 500.00 MiB (125 extents) to 600.00 MiB (150 extents).
Logical volume myswaplv successfully resized.
# mkswap -L newswap /dev/vg01/myswaplv
mkswap: /dev/vg01/myswaplv: warning: don't erase bootbits sectors
on whole disk. Use -f to force.
Setting up swapspace version 1, size = 614396 KiB
LABEL=newswap, UUID=dd91713f-5950-4922-b9a5-e4ea0ec4327e
# swapon -va
swapon on /dev/mapper/vg01-myswaplv
swapon: /dev/mapper/vg01-myswaplv: found swap signature: version 1, page-size 4, same byte order
swapon: /dev/mapper/vg01-myswaplv: pagesize=4096, swapsize=629145600, devsize=629145600
# cat /proc/swaps
Filename Type Size Used Priority
/dev/dm-0 partition 614396 0 -1
You can see after swapoff command, swap volume vanished from /proc/swaps. The newly extended swap of 600MB is back visible after swapon.
How to add swap using file
You can opt to have swap on file rather than volume. This method is a bit easy, quick, and avoids all disk management commands. But along with easiness it involves risk since it’s on a simple file rather than a dedicated disk volume.
First you need to create a blank file with the size of your choice. If you want 8MB swap then 8*1024=8192 block numbers should be used in dd command (since block size used is bs=1024). Do your math accordingly and follow the process below :
Create a blank file with dd
Define file with swap using mkswap
Turn on swap on file using swapon
Check swap
Refer below outputs wherein I created 8MB swap on file.
# dd if=/dev/zero of=/myswapfile bs=1024 count=8192
8192+0 records in
8192+0 records out
8388608 bytes (8.4 MB) copied, 0.0144397 s, 581 MB/s
# mkswap /myswapfile
mkswap: /myswapfile: warning: don't erase bootbits sectors
on whole disk. Use -f to force.
Setting up swapspace version 1, size = 8188 KiB
no label, UUID=40a0f347-ce86-4018-9f4d-7ab76bde02ba
# swapon /myswapfile
# cat /proc/swaps
Filename Type Size Used Priority
/myswapfile file 8188 0 -1
Outputs are pretty self-explanatory. Only calculating dd block count is tricky which I already explained above.
How to add swap using parted disk
Many systems use parted disk management utility in place of LVM. If you are the one then follow the below process for adding swap.
Create a new swap partition (primary, extended or logical) using parted
Setup swap on it using mkswap
Turn on swap on it using swapon
Check swap
Parted should be invoked with the disk name which has free space. I am using a fresh disk here.
# parted /dev/xvdf
GNU Parted 3.1
Using /dev/xvdf
Welcome to GNU Parted! Type 'help' to view a list of commands.
Now, you can view current partition table using print command.
(parted) print
Error: /dev/xvdf: unrecognised disk label
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdf: 1074MB
Sector size (logical/physical): 512B/512B
Partition Table: unknown
Disk Flags:
(parted) mklabel msdos
Since I am using a new disk, I get an unrecognized disk label error. I define label using mklabel msdos. Now create new swap partition using the parted console.
(parted) mkpart primary linux-swap 1 1024
(parted) print
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdf: 1074MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1049kB 1024MB 1023MB primary
(parted) quit
Command mkpart is used to create a partition. Followed by partition type (primary, extended or logical), FS type (swap in this case), the start of the partition (1), and end of partition (1024). After the successful execution of the command, verify the partition table using print again.
Once you are ready with partition, you can even confirm it using fdisk -l command.
# fdisk -l /dev/xvdf
Disk /dev/xvdf: 1073 MB, 1073741824 bytes, 2097152 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000e7301
Device Boot Start End Blocks Id System
/dev/xvdf1 2048 2000895 999424 82 Linux swap / Solaris
You can see the new partition /dev/xvdf1 is created and it’s marked as Linux swap file system type too!
Now you have to enable and on swap on it.
# mkswap /dev/xvdf1
Setting up swapspace version 1, size = 999420 KiB
no label, UUID=1c19e97e-b757-48a0-99a9-68e6162d69c3
# swapon /dev/xvdf1
# cat /proc/swaps
Filename Type Size Used Priority
/dev/xvdf1 partition 999420 0 -1
That’s it! You have turned on the swap in a parted disk partition! To make it persistent over reboots you can add below entry in /etc/fstab.
/dev/xvdf1 swap swap defaults 0 0
This concludes the swap in the Linux article. Comment your suggestions, feedback below.
Learn what is tmpfs, what is the use of tmpfs, what is swap, what is the use of swap and differences between tmpfs, and swap.
tmpfs and swap
On the social share of our last post about RAM disk in Linux we got a comment “what is the difference between RAM disk and SWAP?” So I decided to explain it a bit in an article on our blog. In this post I will try to explain how swap and RAM disk i.e. tmpfs/ramfs is different and how they work.
What is tmpfs?
Tmpfs also mounted as shared memory /dev/shm. tmpfs is a portion of a virtual memory mounted as a file system that helps to speed up applications. It normally is used to transfer data between programs. It appears as a file system but it does not use persistent devices such as a hard disk. Instead it uses virtual memory (a portion of a RAM).
That’s why if you create any file in tmpfs it’s not created on your system disks but in your memory. Whenever you un-mount tmpfs, everything within is lost. Its volatile storage. Even if you add an entry of tmpfs to re-mount at boot, it will be mounted blank. Data does not persist over reboots or shutdowns in tmpfs.
What is SWAP?
swap is a portion of your hard disks used to extend RAM. Its roughly extended RAM by use of persistent storage device. swap only comes in action once your RAM (physical memory) is full. The normal thumb rule is the size of the swap should be double of your physical ram size. But these changes depend on the conditions and system you have. Read how to create extra swap here & check swap on the server.
Even if it uses persistent devices, it still is a volatile memory. It does not hold data over reboot or shutdowns. Since it plays the role of RAM, its characteristics are still of ram even if it uses hard disks.
Difference between tmpfs and swap
tmpfs uses memory while as swap uses persistent storage devices.
tmpfs can be viewed as a file system in df output whereas swap doesn’t
swap has general size recommendations, tmpsfs not. tmpfs size varies on system purpose.
tmpfs makes applications fasters on loaded systems. swap helps the system breathe in-memory full situations.
swap full indicates system heavily loaded, degraded performance, and may crash. tmpfs being full not necessarily means heavy load or prone to crash.
tmpfs is enhancement whereas swap is a must-have feature!
Few observations on why HPUX is losing its grip in the market. How virtualization, cloud, costing effects HPUX existence in the market.
hpux loosing market
Really? HPUX really losing market? Kind of yes. But still it is one of the preferred OS for mission-critical environments like the defense industry because of its reliability and security. HPUX, one of the oldest OS (35 years old) released in 1982, no doubt is one of the best server OS we have seen in decades! Being a core HPUX certified engineer obviously I appreciate it moreover IBM’s AIX and Sun Micro system’s Solaris flavor.
But nowadays I am seeing fewer companies, corporate going for HPUX maybe because of its cost involved. Virtualization, cloud computing, and open-source Linux OS flavors made very cost-effective choices for corporate. High Availability offered by virtualization and cloud computing wins over the reliability of Unix when it comes to making cheap billing. HPUX being a hardware-dependent Os i.e. running only on HP hardware (inexpensive) and also involves costs in OS license itself including prime utilities like glance etc., choosing HPUX is a heavy pocket decision. In today’s world of cost-cutting, obviously this is one of the reasons, companies are not opting for HPUX.
The boom in cloud computing also has an effect on traditional in house data centers and hence on proprietary OS like HPUX. Most of the cloud world is powered by Linux which adversely affects HPUX market share rather altogether AIX, Solaris too. People opting for cloud since they offer cheap services with no maintenance. Even I have seen companies are moving away from HPUX and shifting servers on Linux or cloud for billing numbers.
Another major leap back is HP backed off from new releases of HPUX. It’s like they opt to kill their own lion. The latest HPUX roadmap doesn’t even show HPUX v4 and v5 which was existing in old roadmaps. This clearly indicates they have stopped development for new versions and will be continuing current last HPUXv3 as the latest till 2025. This is a major setback since customers lookout for further development plans of service when opting for it.
I wish HP wake up to new versions and we see HPUX back alive and roaring on the IT world! Still it’s not the end of an era! There are many crucial companies and sectors still run by HPUX cause crucial data needs strong shoulders!
These are my observations and perceptions of HPUX’s current stand-in in the market. Let me know if you have any infographics, new data, matrices, graphs about the HPUX journey to date in comments.
Short tutorial explaining what is RAM disk and how to create a RAM disk in Linux. It also includes differences between ramfs and tmpfs.
RAM disk in Linux
Recently one of our readers asked “how to create a RAM disk in Linux?”. So I thought of writing this small tutorial which will help you to understand what is a RAM disk, what is the use of it and how to create a RAM disk in Linux.
What is RAM disk?
Roughly RAM disk can be termed as a portion of your RAM mounted as a directory. It uses tmpfs or ramfs. Refer below table for the difference between ramfs and tmpfs.
ramfs
tmpfs
Old type
New type and replacing ramfs now
Can not be limited in size
Size limit can be defined
Since can not be limited may lead to system crash
Once limit reached, disk full error written. No system crash issue.
Entry is not visible in ‘df’ output. Need to calculate by using ‘Cached’ number in ‘free’ output.
Can be seen in ‘df’ command output
Work mechanism as file system cache
Work mechanism is as partition of physical disk
RAM disk is a very high speed, high performance and almost zero latency area to store application files. Due to its performance-oriented nature, its mostly used for temporary data like caching application files.
How to create RAM disk?
RAM disk can be created in simple two steps. One is to create a directory on which it should be mounted and the second step is to mount it on that directory using specific FS type. Make sure you have enough free RAM on the system so that portion of it can be used in RAM disk. You can check it using free command.
Lets create directory /mnt/ram_disk and mount RAM disk on it.
In above mount command, -t should be followed by tmpfs or ramfs type. For ramfs, size is the starting size of RAM disk since ramfs have limitless size. Size followed by the name of the disk (of your choice ex. new_ram_disk). You can verify if it mounted properly using df command.
You can see newly created tmpfs of 1GB size is mounted on /mnt/ram_disk (highlighted above).
You can add below entry in /etc/fstab as well to persist it over reboots as well. But keep in mind that data within RAM disk flushes for each reboot since its backed memory is volatile.
Learn networking basics in the Linux server. What is the network route, how to check routes, how to define static and default routes in the Linux system?
Network routes in Linux
Network routes on Linux servers are the paths or gateways packets should follow to reach their destinations. Routes can be configured on interface level and system level. The default route is also known as default gateway is the IP where the packet should discover their path if the current network or interface (from which packet originated on the server) does not know the path for destination IP. This article is about discussing network routes in Linux. It will cover how to define the network route for the network interface, where and how to define the default route or default gateway in Linux etc.
How to check current routes on system?
Current routes on system can be viewed using below commands.
# ip route
default via 172.31.0.1 dev eth0
172.31.0.0/20 dev eth0 proto kernel scope link src 172.31.4.137
# routel
target gateway source proto scope dev tbl
default 172.31.0.1 eth0
172.31.0.0/ 20 172.31.4.137 kernel link eth0
127.0.0.0 broadcast 127.0.0.1 kernel link lo local
127.0.0.0/ 8 local 127.0.0.1 kernel host lo local
----- output clipped -----
You can observe 172.31.0.1 is defined as default gateway on above system.
How to configure static route in Linux?
In RHEL: You need to edit below parameters in the config file /etc/sysconfig/network-scripts/route-ethX.
