top command on Mac OS X is not in CPU order

top command on Mac OS X is not in CPU order. It displays in pid descending order.

To change order, you can start top like

$ top -o cpu

or

$ top -o -cpu

or after starting top, enter 'o' > 'cpu' (or '-cpu') and enter Return key.

A '+' can be prefixed to the key name to specify ascending order.

See `man top` for other supported keys.

Error in yum update on CentOS 6.7 `http://mirror.centos.org/centos/6/SCL/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"`

CentOS release 6.7 (Final)

yum update fails on the error below.

http://mirror.centos.org/centos/6/SCL/x86_64/repodata/repomd.xml: [Errno 14] PYCURL ERROR 22 - "The requested URL returned error: 404 Not Found"
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: scl. Please verify its path and try again

Workaround

$ sudo yum remove centos-release-SCL
$ sudo yum update # Update to CentOS 6.8
$ sudo yum install centos-release-scl
$ sudo yum update

Source: 0010925: Yum update fails on a 404 returned from http://mirror.centos.org/centos/6/SCL/x86_64/repodata/repomd.xml - CentOS Bug Tracker

Paste text into Android emulator or device

$ adb shell input text 'text to paste'
  • For convenience, add the path to adb to PATH environment variable.
    You can find the path to adb in Android Studio [Project Sturcture] > [SDK Location]
  • If multiple devices are connected, specify the serial number of the device by -s option.
    The serial number of the device can be found like below.

    $ adb devices
    
  • Althogh I enclose the text to paste with single quotation marks ('), metacharacters or $0, $1... are extracted by the shell. You should escape them with backslash (\).

Example:

$ adb -s emulator-5554 shell input text 'text to paste'

passenger-config and passenger-status result in an error on CentOS7

passenger-config and passenger-status result in an error on CentOS7.

CentOS Linux release 7.2.1511 (Core)
Apache/2.4.6 (CentOS)
Phusion Passenger 5.0.23 (Installed by `passenger-install-apache2-module`)

$ passenger-config restart-app
*** ERROR: Phusion Passenger doesn't seem to be running. If you are sure that it
is running, then the causes of this problem could be one of:

 1. You customized the instance registry directory using Apache's
    PassengerInstanceRegistryDir option, Nginx's
    passenger_instance_registry_dir option, or Phusion Passenger Standalone's
    --instance-registry-dir command line argument. If so, please set the
    environment variable PASSENGER_INSTANCE_REGISTRY_DIR to that directory
    and run this command again.
 2. The instance directory has been removed by an operating system background
    service. Please set a different instance registry directory using Apache's
    PassengerInstanceRegistryDir option, Nginx's passenger_instance_registry_dir
    option, or Phusion Passenger Standalone's --instance-registry-dir command
    line argument.

Reason

Passenger could not find instance registry directory (PassengerInstanceRegistryDir on Apache, passenger_instance_registry_dir on Nginx).

If instance registry directory is not explicitly specified, default value /tmp is used.
So instance registry dir is made in /tmp. But because Systemd PrivateTmp option is enabled on httpd (default), instance registry dir is created in httpd's private /tmp directory (/tmp/systemd-private-XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX-httpd.service-XXXXXX/tmp). This directory can't be found by other processes such as passenger-config or passenger-status.

This problem owes to Systemd's PrivateTmp, so it may also occurs on RHEL7 or Amazon Linux 2.

Workaround 1: Explicitly specify PassengerInstanceRegistryDir

This workaround remains PrivateTmp enabled.
Explicitly specify Passenger's instance registry directory so that instance registry dir is not made in httpd's private /tmp directory.

(on Apache)
/etc/httpd/conf/httpd.conf

PassengerInstanceRegistryDir /var/run/passenger-instreg

Because files and directories in /var/run (=/run) is deleted on reboot, you must add config file in tmpfiles.d.
See man 5 tmpfiles.d for details.

/etc/tmpfiles.d/passenger.conf

D /var/run/passenger-instreg 0755 root root

You must add PASSENGER_INSTANCE_REGISTRY_DIR for the users who executes passenger-status and passenger-config.

~/.bash_profile

export PASSENGER_INSTANCE_REGISTRY_DIR=/var/run/passenger-instreg

If you use capistrano-passenger, you must set PASSENGER_INSTANCE_REGISTRY_DIR in the stage's deploy recipe because capistrano-passenger executes `passenger-config restart-app`.

set :default_env, {
  ...(omit)..,
  "PASSENGER_INSTANCE_REGISTRY_DIR" => "/var/run/passenger-instreg"
}

Finally restart system.

Workaround 2: Disable PrivateTmp on httpd.service

Copy /usr/lib/systemd/system/httpd.service to /etc/systemd/system and edit it.

/etc/systemd/system/httpd.service

...(omit)
PrivateTmp=false
...(omit)

Then execute below.

$ sudo systemctl daemon-reload
$ sudo systemctl restart httpd.service

Source: CentOS 7 で Phusion Passenger の passenger-status を実行するとエラーとなる - Qiita
お前らもさっさとハマって泣くべきCentOS7の落とし穴4つ - Qiita
Handle systemd PrivateTmp #1475
Systemd入門(5) - PrivateTmpの実装を見る - めもめも