Setting Up Git Remote Repositories When you initialize a new repository locally and try to push to GitHub or Bitbucket for the first time, you’ll likely encounter errors like: No refs in common and none specified; doing nothing. Perhaps you should specify a branch such as ‘master’. fatal: The remote end hung up unexpectedly This…
Getting the script’s own path in a sourced Bash script When you source a script using . script.sh or source script.sh, the $0 variable doesn’t point to the sourced script—it stays as the path of the parent shell or calling script. This creates a problem if you need the sourced script to know its own…
Testing for user existence on Linux When writing system administration scripts, you often need to check if a user account exists before taking action. There are several reliable methods to accomplish this. Using id command The id command retrieves user information and returns a non-zero exit code if the user doesn’t exist. This makes it…
Moving to a specific byte in Vim If you need to jump to a particular byte position in a file, Vim provides the goto command. This is useful when debugging binary files, working with hex editors, or when error messages reference byte offsets. Using the goto command In normal mode, press go followed by the…
Installing MATE Desktop on Linux Mint If you’re running Linux Mint and want to install the MATE desktop environment, you’ll need to use the appropriate metapackage for your distribution. Using apt The standard approach for most Linux Mint versions is to install the mint-meta-mate metapackage: sudo apt install mint-meta-mate Note that aptitude is largely obsolete…
Enable natural scrolling on touchpad in MATE MATE’s mouse settings don’t include a graphical toggle for natural (or inverted) scrolling on touchpads, unlike GNOME or Cinnamon. You’ll need to configure it through the command line or configuration files. Using synclient If your system uses Synaptics touchpad driver, you can invert scrolling direction with synclient: synclient…
Getting a User’s Home Directory from a Variable in Bash The tilde expansion ~username works fine when the username is literal, but fails when the username is stored in a variable like ~$user. Bash doesn’t perform tilde expansion on variables by default—it only expands ~ at the beginning of a word before variable expansion happens….
Generating a CSR from a Private SSL Key When renewing an SSL certificate, your CA will request a Certificate Signing Request (CSR). If you have the private key but need to generate a fresh CSR, OpenSSL handles this straightforwardly. Basic CSR Generation Generate a CSR from your existing private key: openssl req -new -key ssl.key…
Linux boots failed with “sulogin: can not open password database” while the /etc/passwd and /etc/shadow files look fine. How to fix this? The OS is Fedora 41. You may try this trick Step 1: boot Linux with rw init=/bin/bash following this tutorial. Step 2: after Linux booted, disable SELinux following this tutorial. Reboot. If it…
I have a text file with many lines of text. In Linux, how to sort the lines by their length? You can make use of awk together with the sort program like awk ‘{ print length(), $0 | “sort -n” }’ /path/to/text/file Here, we use awk to calculate the text length and sort -n to…
How to Test if a String Contains a Substring in Bash Bash provides several ways to check for substrings. The Code if [[ “$string” == *”substring”* ]]; then echo “Found it!” fi Bash in 2026 In 2026, the [[ … ]] double-bracket syntax is the standard for string testing in Bash 5.x. It supports glob…
I am writing a Bash script accepting input of a path from the user. I want to make the path have no trailing ‘/’, such as ‘/path/to/dir’ instead of ‘/path/to/dir/’. However, as the input is from the user, the input could be ‘/path/to/dir’. My script is intended to handle this. The question is: how to…
How to get a script’s directory reliably in Bash on Linux? For example, to get the directory of the executing script $0. dirname can give you the directory name from the absolute path. You can get the absolute path of the script by readlink -f to handle symbolic links (consider a symbolic link ./run.sh linked…
`xargs` passes the argument once to the utility command specified. For example, xargs cat will cat every line passed to xargs. But how to use the xargs argument twice in the command on Linux? For example, to rename file to file.bak where file is from the stdin. One solution is to write a small script like…
The command using ‘;’ after ‘&’ like ssh host1 hostname &; ssh host2 hostname & Leads to error like bash: syntax error near unexpected token `;’ Why does ; after & lead to unexpected token error in bash on Linux? And what’s the solution? The fix The quick fix is to change your command to…
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…
How to Watch a Directory Size in Linux Monitoring directory growth is useful for logs or temporary files. The Commands Real-time: watch -n 1 du -sh /path/to/dir Interactive: ncdu /path/to/dir Linux in 2026 In 2026, ncdu (NCurses Disk Usage) is the go-to tool for interactive directory analysis. It’s fast, visual, and allows you to delete…
When you write your master thesis (in Chinese) on windows, you may have following worries. a, Be afraid your master thesis is lost (or can not be accessed) when hard disk/udisk is broken (or something other viruses). b, Keep master thesis availability (7×24) and safety. c, Do not want anyone else to access it before…
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…
How to cut by multiple spaces in Linux? For example, if I get a string like a b c d where the spaces among the fields are not decided. How to get the four fields a, b, c and d out? Here, we take getting ‘b’ (the 2nd field) as the example. You can first…