This is a quick guide on how to configure and use SGID, SUID and the sticky bit on Linux. I will not get into a lot of details, but I will add comments and notes that might help you understand or overcome a few common issues.

SUID - Set-user Identification

When a command or script with SUID bit set is run, its effective UID becomes that of the owner of the file, rather than of the user who is running it.

-rws-----

Note: SUID does not work on scripts that start with a shebang (#!)

# chmod u+s [file]
-rwsr--r--. 1 root root 0 Mar 16 21:48 test

# chmod 4744 [file]
-rwsr--r--. 1 root root 0 Mar 16 21:48 test

Note: A capital ’S’ (-rwSr–r–) indicates that the execute bit is not set

SGID - Set-group identification

SGID permission is similar to the SUID permission. The main difference is that when a script or command with SGID set is run, it runs as if it were a member of the same group in which the file is a member.

-rwxr-sr--

Setting SGID

# chmod g+s [file]
-rwxr-sr--. 1 root root 0 Mar 16 21:48 test

# chmod 2754 [file]
-rwxr-sr--. 1 root root 0 Mar 16 21:48 test

Note: A capital ’S’ (-rwxr-Sr–) indicates that the execute bit is not set

Sticky bit

Anyone can write, but only the owner can delete the files (just like /tmp).

drwxrwxrwt

Sticky bit is usually set on directories. Setting the sticky bit on a folder does nothing (on Linux).

Setting sticky bit

# chmod o+t [dir]
-rwxr-r-t. 1 root root 0 Mar 16 21:48 test

# chmod 1755 [dir]
-rwxr-xr-t. 1 root root 0 Mar 16 21:48 test

Notes:

• A capital ’T’ indicates that the execute bit is not set
• You should give write permission to make sure that the target users can write to the folder

Additional Special Permissions

A . can represent special permissions (SELinux related).

-rw-rw-rw-.  

A + indicates ACLs are applied.

-rw-rw-rw-+

Cheat Table

Note: Octal mode is not an absolute translation to symbolic mode as symbolic changes only the specified permission set (user, group OR others), while octal overwrites all permission sets (user, group AND others)

On this tutorial I will show you how to install and configure TLP and Intel P-state and CPUFreq Manager on your ThinkPad P1 Gen 2 (with KDE Arch).

If you don’t know, TLP allows you to configure specific rules to help optimize the battery life on your laptop, while Intel P-state and CPUFreq Manager gives you a pretty interface via a tray icon that allows you to control CPU/GPU frequencies and a few power profiles.

TLP

Using TLP’s threshold functionality we can change the charge thresholds for the battery. On ThinkPads the charging process is controlled by the embedded controller (EC) firmware (instead of software running on the operating system). Lenovo’s default settings start charging when the battery drops below 96%, and stops at 100%. This is good for “performance” but it deteriorates the battery causing a shorter lifespan. By changing the battery charge thresholds with TLP we can extend the lifespan of the battery.

Note: Lithium-ion batteries do not suffer from memory effect like NiCd and NiMH batteries. See the quote below (https://batteryuniversity.com) for an explanation

A lithium-ion battery provides 300-500 discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery. There is no concern of memory when applying unscheduled charges.

Installation

This part is very simple. Install the following packages and then reboot:

=> Main

• tlp
• acpi_call
• smartmontools

=> AUR

• tlpui-git

Configuration

a. Run tlpui and go to the ‘ThinkPad Battery’ tab on the left

b. Set the following parameters/options

START_CHARGE_THRESH_BAT0

Value = 50/60

This is the threshold of when the battery will start charging. If you set it to 50 the battery will only start charging when it’s below 50%.

STOP_CHARGE_THRESH_BAT0

Value = 70/80

This is the value of when the battery will stop charging. If you set it to 80 the battery will stop charging when close to %80.

RESTORE_THRESHOLDS_ON_BAT

Value = enabled

When you bypass the charge thresholds with a TLP command you would usually need to reboot your machine to reset the thresholds. When RESTORE_THRESHOLDS_ON_BAT is enabled the configured thresholds will be restored when the power is unplugged.

This is useful if you need to fully charge your battery for a meeting, or to work in a place where you know you won’t have a power outlet.

NATACPI_ENABLE

Value = enabled

TPACPI_ENABLE

Value = enabled

TPSMAPI_ENABLE

Value = disabled

tp_smapi doesn’t support newer models, so we need to disable this.

c. Go back to the ‘General’ tab and enable TLP_ENABLE

d. Click on ‘save’ and reboot

Additional TLP Commands

Get a full report from TLP

sudo tlp-stat

Get a report with battery information only

sudo tlp-stat -b

Temporarily bypass the current config and use specified threshold

sudo tlp setcharge [start threshold] [stop threshold]

Bypass thresholds and fully charge battery

sudo tlp fullcharge

Bypass the start threshold and charge up to the stop threshold

sudo tlp chargeonce

Intel P-state and CPUFreq Manager

a. Install plasma5-applets-plasma-pstate (AUR)

b. Add the widget to your panel

c. Done! You should now be able to use the widget for basic control

Reference:

• https://linrunner.de/tlp/faq/battery.html
• https://support.lenovo.com/ca/en/solutions/ht078208
• https://wiki.archlinux.org/index.php/TLP
• https://store.kde.org/p/1282623/

A quick explanation and visual overview of the AWS Route 53 policies (with the exception of Geoproximity Routing).

Simple Routing Policy

Use for a single resource that performs a given function for your domain, for example, a web server that serves content for the example.com website.

Important points to remember:

• Simplest routing policy
• Only one DNS record set
• Multiple IP address per record set can be used
• Values are returned to user in random order
• No health checks

Weighted Routing Policy

Weighted Routing Policy controls the percentage of the requests that go to a specific endpoint.

Important points to remember:

• Weighted routing sends user traffic based on the weight that you supply
• You can split traffic between different regions
• Multiple IP address per record set can be used
• Health checks can be used

Latency Routing Policy

Use when you have resources in multiple AWS Regions and you want to route traffic to the region that provides the best latency.

Important points to remember:

• Routing will be based on user to region latency
• Multiple IP address per record set can be used
• Health checks can be used

Failover Routing Policy

Use failover routing policy when you want to configure active-passive failover.

Important points to remember:

• Use failover routing policy when you want to configure active-passive failover
• Health checks
  • You can’t save the primary record without a health check
  • The secondary record can be created without a health check

Geolocation Routing Policy

Geolocation routing lets you choose the resources that serve your traffic based on the geographic location of your users, meaning the location that DNS queries originate from.

Important points to remember:

• This is routing based on user’s location
• Multiple IP address per record set can be used
• Health checks can be used

Multivalue Answer Routing policy

Use when you want Route 53 to respond to DNS queries with up to eight healthy records selected at random.

Important points to remember:

• It’s very similar to simple routing, but with two differences:
  • You can have multiple record sets
  • You can have health checks

This post will show you how to change line movement and control key bindings in macOS to be similar to what we use in Linux (and windows).

The following keyboard shortcuts will be added:

Instructions

a. First create the folder ~/Library/KeyBindings/ and then the file DefaultKeyBinding.Dict

mkdir ~/Library/KeyBindings/
vim DefaultKeyBinding.Dict

b. Add the contents below to the new file:

{
    /* Ctrl + Left */
    /* "^\UF702"  = "moveWordLeft:"; */
    "@\UF702"  = "moveWordLeft:";

    /* Ctrl + Right */
    /* "^\UF703"  = "moveWordRight:"; */
    "@\UF703"  = "moveWordRight:";

    /* Ctrl + Shift + Left */
    /* "^$\UF702" = "moveWordLeftAndModifySelection:";*/
    "@$\UF702" = "moveWordLeftAndModifySelection:";

    /* Ctrl + Shift + Right */
    /* "^$\UF703" = "moveWordRightAndModifySelection:";*/
    "@$\UF703" = "moveWordRightAndModifySelection:";

    /* Remap Home / End keys */
    /* Home Button*/
    "\UF729" = "moveToBeginningOfLine:";
    /* End Button */
    "\UF72B" = "moveToEndOfLine:";

    /* Shift + Home Button */
    "$\UF729" = "moveToBeginningOfLineAndModifySelection:";

    /* Shift + End Button */
    "$\UF72B" = "moveToEndOfLineAndModifySelection:";

    /* Ctrl + Home Button */
    /* "^\UF729" = "moveToBeginningOfDocument:"; */
    "@\UF729" = "moveToBeginningOfDocument:";

    /* Ctrl + End Button */
    /* "^\UF72B" = "moveToEndOfDocument:"; */
    "@\UF72B" = "moveToEndOfDocument:";

    /* Shift + Ctrl + Home Button */
    /* "$^\UF729" = "moveToBeginningOfDocumentAndModifySelection:"; */
    "$@\UF729" = "moveToBeginningOfDocumentAndModifySelection:";

    /* Shift + Ctrl + End Button*/
    /* "$^\UF72B" = "moveToEndOfDocumentAndModifySelection:"; */
    "$@\UF72B" = "moveToEndOfDocumentAndModifySelection:";
}

Note: The code above assumes you are have substituted the Command Key for the Control Key in “Keyboard => Modifier Keys…” (see screenshot below). If you haven’t, you can try changing the comment between the commented and uncommented blocks.

c. Restart the application you want to use

Reference:

• https://gist.github.com/trusktr/1e5e516df4e8032cbc3d

Now here’s a cool and quick way to share your WiFi SSID and password from a terminal window with a guest.

You can use qrencode to generate a QR code with the parameters below:

WIFI:S:[Your SSID here];T:WPA;P:[Your Password Here];;

For example, let’s pretend my SSID is MySweetSSID and my password is mysecretpassword. We can run:

qrencode -o - -t utf8 'WIFI:S:MySweetSSID;T:WPA;P:mysecretpassword;;'

To get: