Separation Anxiety: A Tutorial for Isolating Your System with Linux Namespaces

With the advent of tools like Docker, Linux Containers, and others, it has become super easy to isolate Linux processes into their own little system environments. This makes it possible to run a whole range of applications on a single real Linux machine and ensure no two of them can interfere with each other, without having to resort to using virtual machines. These tools have been a huge boon to PaaS providers. But what exactly happens under the hood?

Fix fonts quickly with auto-hinting

Very quick hack to fix the font hinting automatically. Just execute the below:

sudo ln -s /usr/share/fontconfig/conf.avail/10-autohint.conf /etc/fonts/conf.d/10-autohint.conf

After this you should see the font hinting enabled and thus better experience with fonts.

power saving on laptop

One of the easiest way to make sure that you can have a decent battery life is

sudo yum install tlp smartmontools
sudo systemctl enable tlp
sudo systemctl start tlp

And after this you can check the status like this:

sudo tlp stat
— TLP 0.9 ——————————————–

+++ Configured Settings: /etc/default/tlp
TLP_ENABLE=1
TLP_DEFAULT_MODE=AC
DISK_IDLE_SECS_ON_AC=0
DISK_IDLE_SECS_ON_BAT=2
MAX_LOST_WORK_SECS_ON_AC=15
MAX_LOST_WORK_SECS_ON_BAT=60
SCHED_POWERSAVE_ON_AC=0
SCHED_POWERSAVE_ON_BAT=1
NMI_WATCHDOG=0
ENERGY_PERF_POLICY_ON_AC=performance
ENERGY_PERF_POLICY_ON_BAT=powersave
DISK_DEVICES=”sda sdb”
DISK_APM_LEVEL_ON_AC=”254 254″
DISK_APM_LEVEL_ON_BAT=”128 128″
SATA_LINKPWR_ON_AC=max_performance
SATA_LINKPWR_ON_BAT=min_power
AHCI_RUNTIME_PM_TIMEOUT=15
PCIE_ASPM_ON_AC=performance
PCIE_ASPM_ON_BAT=powersave
RADEON_POWER_PROFILE_ON_AC=high
RADEON_POWER_PROFILE_ON_BAT=low
RADEON_DPM_STATE_ON_AC=performance
RADEON_DPM_STATE_ON_BAT=battery
RADEON_DPM_PERF_LEVEL_ON_AC=auto
RADEON_DPM_PERF_LEVEL_ON_BAT=auto
WIFI_PWR_ON_AC=off
WIFI_PWR_ON_BAT=on
WOL_DISABLE=Y
SOUND_POWER_SAVE_ON_AC=0
SOUND_POWER_SAVE_ON_BAT=1
SOUND_POWER_SAVE_CONTROLLER=Y
BAY_POWEROFF_ON_BAT=0
BAY_DEVICE=”sr0″
RUNTIME_PM_ON_AC=on
RUNTIME_PM_ON_BAT=auto
RUNTIME_PM_ALL=1
RUNTIME_PM_DRIVER_BLACKLIST=”radeon nouveau”
USB_AUTOSUSPEND=1
USB_BLACKLIST_WWAN=1
RESTORE_DEVICE_STATE_ON_STARTUP=0

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xsos – a tool for sysadmins and support

Here is a very nice article that you may find useful

https://access.redhat.com/discussions/469323

ssh – remove offending key.

Whenever a system/server is re-installed or the host key changed for any reason, you would have seen the “host key verification failed”. And as usual you would have to go to known_hosts file and delete the offending key. I will show you 2 simple ways to do this here.

The output that you get in such scenario is:

Offending ECDSA key in ~/.ssh/known_hosts:4

First, you can use sed to directly delete the offending key with a command like this :

How to verify sha256sum for multiple file or one file.

So, lets say you have downloaded the SHA256SUMS files. This file contains the sha256sum for multiple files and you want to compare the values for only one or some of them, then the simplest thing you can do is:

sha256sum -c SHA256SUMS

Now, with this if you do not have some files present then you might get some errors and if you do not want that, then you can try this:

Executing commands on multiple hosts

If you have to execute the same command in multiple hosts, then you can use mussh:

Description : Mussh is a shell script that allows you to execute a command or script

over ssh on multiple hosts with one command. When possible mussh will use

ssh-agent and RSA/DSA keys to minimize the need to enter your password

more than once.

First install mussh with the following command

dnf install mussh

Now to run this for multiple hosts, you can run like this