In the realm of cryptography, handling and managing keys is a crucial task. The command provided is a series of operations using OpenSSL and other command-line utilities to extract and format an elliptic curve (EC) public key. Let’s break down the command to understand its purpose and functionality. The Command Extracting EC Public Keys with…
Email sender fraud is an annoying problem. Malicious email senders send spam emails with email senders that are under non-authorized domain names. This may affect the reputation of the domains used by the fraud sender. On another hand, lots emails will be rejected and reverted back, which causes lots additional work to the domain administrators….
In a Linux system, we may have multiple kernels installed. Usually, it is the latest kernel configured to be the default one the system boot loader will use during automatic boot if there is no manual kernel choosing. In many cases, such as there is no driver ready yet for some devices in newer kernels,…
Perl one-liners with perl’s regular expression statement can be a very powerful text processing tools used as commands in a terminal or a script. By default, the input to the perl one-liner with -p or -n options is passed line by line. However, when we want to match multiple lines, it gets us some trouble….
grep is excellent to match patterns from STDOUT/text files in command line or scripts. It’s handy. Sometimes, our problem is more complex than finding a keyword from a file. On a first thought, it may sound impossible using grep for such complex problems. But grep can be quite powerful than we thought. Today, let’s check…
Hello! Im trying to create a screen folder for the user apache, Not root. But it seems to fail, I have no idea on how to fix this issue. I only get the error: Cannot make directory ‘/var/run/screen/S-apache’: Permission denied Im using Cent OS 7 There may be various possible reasons. 2 common reasons: screen…
Where is MySQL / MariaDB storage location by default on CentOS 7? No special configuration to the MariaDB from official repository of CentOS. On CentOS 7 Linux it is usually by default /var/lib/mysql But here I give you another “hacky” way to find it out. The method is to find out the mysql daemon mysqld’…
How to find out all files with replication factor 1 in HDFS? The hdfs dfsadmin -report shows there are blocks with replication factor 1: Missing blocks (with replication factor 1): 7 How to find them out? You can run hdfs fsck to list all files with their replication counts and grep those with replication factor…
It is useful to monitor a server node’s temporary. Among all the sensors’ temperatures, the higher one may be a very important one. How to get the highest temperature from all sensors in a server on Linux? You can use this command to get the the highest temperature from all sensors in a server on…
WPS’ wpp program reports “libbz2.so.1.0: cannot open shared object file” on CentOS 7 as follows: $ wpp /opt/kingsoft/wps-office/office6/wpp: error while loading shared libraries: libbz2.so.1.0: cannot open shared object file: No such file or directory The reason: wpp will tries to dynamically link ‘libbz2.so.1.0’ $ ldd /opt/kingsoft/wps-office/office6/wpp | grep libbz2 libbz2.so.1.0 => not found libbz2.so.1 =>…
Question: how to find the disk where the Linux’s root(/) is on in Bash? The root may be on a LVM volume or on a raw disk. 2 cases: One example: # df -hT | grep /$ /dev/sda4 ext4 48G 32G 14G 71% / For another example: # df -hT | grep /$ /dev/mapper/fedora-root ext4…
How to grep a tab on Linux? Including ‘t’ seems not working. grep can grep tabs. The problem is likely the tab is not passed to grep. If you are using Bash, you can use ANSI-C quoting to pass the “tab” to grep: $ grep $’t’ file.txt Or, use Perl-style regex (only for GNU grep)…
Most modern servers or computers have sensors to detect the temperature of various components. On Linux, how to get the CPU core temperatur in command linux? First, make sure the package “lm-sensors” is installed on your Linux and the command sensors works for you. Then, you can use this piece of script to get the…
How to get the $PATH environment variables of another user in Bash on Linux? The current user running the Bash script is root. If the scripts is run by root, this piece of code will store the PATH from the environment of the user user1: user1path=$(su – $user1 -c env | grep ^PATH= | cut…
How to get the top committers in git? Like in github: But plain text is fine showing number of commits and author names/emails sorted by the number of commits. You may use this command: git log | grep Author | sort | uniq -c | sort -n -r Here, count the number of commits by…
stop-dfs.sh report that there are no datanodes running on some nodes like hdfs-node-000208: no datanode to stop However, there are DataNode process running there. How to clean these processes on many (100s) of nodes? You may use this piece of bash script: for i in `cat hadoop/etc/hadoop/slaves`; do echo $i; ssh $i ‘jps | grep…
The samtools merge can merge bam files while it can not work for sam files. How to merge sam files on Linux? According to the sam format specification, header lines start with @, while alignment lines do not. So you can use grep to merge sam files as follows efficiently. Assume the header is from…
We know that we can disable USB 3.0 in the BIOS. But is there a way to force a USB 3.0 port to work in USB 2.0 mode inside of a running Linux? On Linux on some platforms booted in BIOS modes, you can use the following command to force USB 2.0 modes for your…
I am looking for a better method for getting the latest commit’s hash in git. I know git log -1 can show the info of the latest commit and from the info of the latest commit I can use grep and other tools to get the hash. Is there better method supported from git? Note:…
I keep seeing messages in dmesg as follows with “exception Emask 0x10” -> “SError: { UnrecovData 10B8B BadCRC }” -> “failed command: READ FPDMA QUEUED” -> “hard resetting link”: [ 7395.936692] ata4.00: exception Emask 0x10 SAct 0xe000 SErr 0x280100 action 0x6 frozen [ 7395.936701] ata4.00: irq_stat 0x08000000, interface fatal error [ 7395.936703] ata4: SError: {…