TOPIC: CRYPTOGRAPHIC SOFTWARE
Changing tab titles in the macOS Terminal app using the command line
25th December 2024One thing that I have noticed with the macOS terminal app that I have not seen with its Linux counterparts is that the tab titles can get stuck after an SSH session to a remote server. Thus, I decided to see if they could be changed or reset. Handily, a single command will do just that:
echo -ne "\033]1;New Tab Title\007"
In a UNIX shell (BASH, ZSH, etc.), the echo command outputs text, and it is the text that changes a tab title. Here, the -ne options both negate the generation of a newline (which would be the function of the -n switch if used on its own) and interprets the escape characters included in the text (which would be the function of the -e switch if used on its own).
Within the text string \033 is the octal representation of the escape character that initiates the control sequence that follows it. This is ]1;, the Operating System Sequence (OSC) for setting the tab title in this case, more generally the icon and window title in other circumstances. The text New Tab Title should be self-explanatory, while \007 is the octal representation of the bell character (BEL) that terminates the OSC.
Because I wanted to have the current working directory path as the title, I made a small modification to do this dynamically:
echo -ne "\033]1;$(pwd)\007"
It is the $(pwd) portion that does just that, taking the output of the pwd command and adding it into the string. Thus, I see what is open in each tab. That stopped me ending up in the wrong one, and I even added an alias into the .zshrc file to make it easier to invoke. The functionality may be a more general UNIX or Linux feature, though I have not had opportunity or reason to try it just yet.
What to do when a GPG signature becomes invalid for a package repository on Linux Mint
12th September 2024During a package update on my main Linux system, I encountered the following kind of error message:
An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://cli.github.com/packages stable InRelease: The following signatures were invalid: EXPKEYSIG <GPG Key> GitHub CLI
The message indicated a problem with the GPG signature verification for the GitHub CLI repository. The cause was that the signature for the repository was invalid, preventing the package manager from updating the repository's index files. The first step then was to remove the invalid GPG key using the following command:
sudo apt-key del <GPG Key>
With the invalid GPG key removed, the next step is to add the new GPG key for the GitHub CLI repository by issuing the following command:
curl -fsSL https://cli.github.com/packages/githubcli-archive-keyring.gpg | sudo tee /usr/share/keyrings/githubcli-archive-keyring.gpg > /dev/null
Once I had the new GPG key, I was able to use my usual system update process without any problem. The error message was gone, and updates and upgrades proceeded as intended.
Remedying a warning about an ECDSA host key
25th August 2024During some website maintenance that I have been doing using my iMac, I encountered a message like the following at one point:
Warning: the ECDSA host key for '<server name>' differs from the key for the IP address '<server IP address>'
The cause was a rebuild of one of my web servers and changes to SSH keys that it caused. The solution in my case was to issue a command like the following:
ssh-keygen -R <server IP address>
That felt neater than editing ~/.ssh/known_hosts to remove the affected key. If the command does not remedy things for you, then editing the file should help. That, after all, is what the rest of the warning message suggested to me. My qualms about messing with files made me go with the command, and that got things sorted. There had been some use of ssh-copy-id too, which might be information that is worth having to hand.
Automated entry of SSH passwords
17th February 2022A useful feature for shell scripting is automatic password entry when logging into other servers. This often involves plain text files, which are not secure. Fortunately, I found an alternative. The first step is to use the keygen tool included with SSH. The command is shown below. The -t switch defines the key type, RSA in this example. You can add a passphrase, but I chose not to for convenience. You should evaluate your security requirements before implementing this approach.
ssh-keygen -t rsa
The next step is to use the ssh-copy-id command to generate the keys for a set of login credentials. For this, it is better to use a user account with restricted access to keep as much server security as you can. Otherwise, the process is as simple as executing a command like the following and entering the password at the prompt for doing so.
ssh-copy-id [user ID]@[server address]
Getting this set up has been useful for running a file upload script to keep a web server synchronised, and it is better to have the credentials encrypted rather than kept in a plain text file.