Category: Linux

Using fc to Edit and Re-execute Bash Commands

Posted on by rchapin

I recently learned about the Bash built-in fc. It is a great tool that enables you to edit and re-execute commands from your bash history.

Oftentimes there is a command in your history that instead of just grepping through the history and then re-executing as-is you’ll want to make a modification or two. With fc you can first edit it in your favorite editor and then when closing the editor fc will execute the command.

For me, vim is my → Continue reading “Using fc to Edit and Re-execute Bash Commands”

Renaming Terminator Tabs Under XFCE4

Posted on by rchapin

Sometimes I need to have quite a few tabs open in a terminal window. For some reason, under XFCE4 when I press CTRL+Alt+A, which is defined as the keyboard shortcut to rename a tab, it hides the window.

The only way that I was able to get it to work was to re-label the shortcut to CTRL+Alt+Z under PreferencesKeybindings in Terminator.→ Continue reading “Renaming Terminator Tabs Under XFCE4”

Configuring rsyslog to rotate log files from log messages streamed to it from a Systemd service

Posted on by rchapin

In general, I have moved to writing all of my applications to write their log output to STDOUT. This makes running them on the command line, in an IDE, on a bare metal box, VM, or in a container completely decoupled from how you store and view the logs. No more having multiple logging configs for each flavor of deployment.

In this particular case, I am running an application in a container (but it isn’t necessary that it is in → Continue reading “Configuring rsyslog to rotate log files from log messages streamed to it from a Systemd service”

Edit a Range of Lines Using sed

Posted on by rchapin

Let’s say that you have a range of lines in a source file (lines 11 – 17) that you want to comment out with a ‘#’ and a space character before the line.

To do that, you would use sed, specifying a range of lines and then specify a replacement command with a capture group as follows:

sed '11,17{s/\(\w\)/\# \1/}' filename.py
→ Continue reading “Edit a Range of Lines Using sed”

How To Compile and Install New SELinux Plicy Modules

Posted on by rchapin

Following is a quick how-to on compiling and adding addition SELinux modules.

When configuring and deploying new and/or custom services on systems that are enforcing SELinux you will likely have to compile addition SELinux modules.

This how-to includes how to go through each step of compiling a new module one-by-one; similar to the model of breaking down the compilation of C and C++ into it’s composite steps.

Step 1:  Gather the audit.log entries

You will need to determine which → Continue reading “How To Compile and Install New SELinux Plicy Modules”

Adding a New Disk to a Linux Server and Creating an LVM Partition

Posted on by rchapin

There are a number of tutorials online for adding a new disk to a machine and then extending an existing LVM partition to use the new device.

This particular tutorial covers the use case of adding a new disk to a Linux server and then creating a NEW LVM partition on it without modifying the existing devices and LVM partitions.

The first thing you will need to do is add the physical device to the server (or VM).

Then, you → Continue reading “Adding a New Disk to a Linux Server and Creating an LVM Partition”

[SOLVED] Unable to Customize Keyboard Shortcuts for Switching Between More Than 4 Workspaces in GNOME on CentOS 7 or RHEL 7

Posted on by rchapin

I am working on a VM that is running GNOME under RHEL 7 and I typically run with 12 workspaces.  The default GNOME install only has the keyboard shortcut configurations up to “Switch to workspace 4”.

It turns out that the solutions is to use the gsettings cli tool to add additional shorcuts.

$ gsettings set org.gnome.desktop.wm.keybindings switch-to-workspace-5 "[\"<ControlF5\"]"
$ gsettings set org.gnome.desktop.wm.keybindings move-to-workspace-5 "[\"<Alt5\"]"
→ Continue reading “[SOLVED] Unable to Customize Keyboard Shortcuts for Switching Between More Than 4 Workspaces in GNOME on CentOS 7 or RHEL 7”

How to See SELinux Denials That Do Not Show In the audit.log

Posted on by rchapin

Or, otherwise know as: SELinux and Silent Denials.

Sometimes when troubleshooting SELinux issues, you will have added new policies for each of the denial causes written to the audit.log, but SELinux will still be denying access . . . and not giving you any further information about it in the audit.log.

Various processes often execute additional system calls that are above an beyond what they need to do for normal operation.  Many of them are blocked, and in order to → Continue reading “How to See SELinux Denials That Do Not Show In the audit.log”

Mounting a Samba Share From Linux Client to Linux Samba Server

Posted on by rchapin

In order to be able to access a Samba share on a remote client as a mounted file system execute the following command, as root on the client:

mount -t cifs -o user=<user-on-samba-share,uid=<uid-on-local-macheine,gid=<gid-on-local-machine,rw,workgroup=<your-workgroup//ip/share /mnt/mount-point-dir

You will be prompted for the password for the user defined on the Samba server.

If you are able to authenticate, and then get the following error:

ls: reading directory .: Permission denied

Check the SELinux context type of the directory on → Continue reading “Mounting a Samba Share From Linux Client to Linux Samba Server”

© 2005 Ryan Chapin