If you use sudo to run commands as root, you've probably run into “permission denied” problems when only part of a pipeline or part of a command is running with root permissions.
This fails with “permission denied” because the file is writable only by root:
$ echo 12000 > /proc/sys/vm/dirty_writeback_centisecs
But, this fails too:
$ sudo echo 12000 > /proc/sys/vm/dirty_writeback_centisecs
Why? The /bin/echo program is running as root, because of sudo, but the shell that's redirecting echo's output to the root-only file is still running as you. Your current shell does the redirection before sudo starts.
The solution is to run the whole pipeline under sudo. There are a couple ways to do it, but I prefer:
echo "echo 12000 > /proc/sys/vm/dirty_writeback_centisecs" | sudo sh
That way, I can type everything before the pipe character, and see what I'm about to run as root, then press the up arrow and add the | sudo sh to do it for real. This is not a big deal for short, obvious pipelines, but when you're building up a more complicated command as root, it's safer to look at it first before you run it.
To see the interrupts occurring on your system, run the command:
# watch -n1 "cat /proc/interrupts" CPU0 CPU1 0: 330 0 IO-APIC-edge timer 1: 11336 0 IO-APIC-edge i8042 4: 2 0 IO-APIC-edge 6: 3 0 IO-APIC-edge floppy ... NMI: 0 0 Non-maskable interrupts LOC: 5806923 6239132 Local timer interrupts ...
The -n1 option passed to watch causes the specified command to be re-run every second.
Getting Started with DevOps - Including New Data on IT Performance from Puppet Labs 2015 State of DevOps Report
August 27, 2015
12:00 PM CDT
DevOps represents a profound change from the way most IT departments have traditionally worked: from siloed teams and high-anxiety releases to everyone collaborating on uneventful and more frequent releases of higher-quality code. It doesn't matter how large or small an organization is, or even whether it's historically slow moving or risk averse — there are ways to adopt DevOps sanely, and get measurable results in just weeks.
Free to Linux Journal readers.Register Now!
|A Project to Guarantee Better Security for Open-Source Projects||Aug 27, 2015|
|Concerning Containers' Connections: on Docker Networking||Aug 26, 2015|
|My Network Go-Bag||Aug 24, 2015|
|Doing Astronomy with Python||Aug 19, 2015|
|Build a “Virtual SuperComputer” with Process Virtualization||Aug 18, 2015|
|Firefox Security Exploit Targets Linux Users and Web Developers||Aug 17, 2015|
- Concerning Containers' Connections: on Docker Networking
- Problems with Ubuntu's Software Center and How Canonical Plans to Fix Them
- My Network Go-Bag
- Firefox Security Exploit Targets Linux Users and Web Developers
- Doing Astronomy with Python
- A Project to Guarantee Better Security for Open-Source Projects
- Build a “Virtual SuperComputer” with Process Virtualization
- diff -u: What's New in Kernel Development
- Three More Lessons
- Django Models and Migrations