Category: Linux

yum-config-manager

yum-config-manager allows you to manage yum repositories.

To add a repo, run

yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo

Disable a repository

yum-config-manager --disable rpmfusion-free-updates

See yum

August 9, 2019

Start MongoDB from command line
To start MongoDB from command line, run
```
mongod --auth --dbpath /path/to/mongodb
```
See MongoDB
August 9, 2019
Remote Desktop
Remote Desktop Software

https://guacamole.apache.org
Google Chome Remote Desktop
https://rustdesk.com – Free Open source teamviewer alternative.

Enable Remote Desktop
See vnc
August 7, 2019

Ubuntu allow a normal user to edit WiFi Connection

When a normal user edit Wi-Fi connection on Wi-Fi Settings, they will be asked to enter administrator user pasword.

To allow a normal user to modify network connection, you can edit the connection configuration file in folder

/etc/NetworkManager/system-connections

This file look like

root@sok-01:/etc/NetworkManager/system-connections# cat SOK
[connection]
id=SOK
uuid=982596a7-44c8-4e52-a696-6acf4daeec12
type=wifi
permissions=

[wifi]
mac-address=E8:DE:27:0B:39:55
mac-address-blacklist=
mode=infrastructure
ssid=SOK

[wifi-security]
auth-alg=open
key-mgmt=wpa-psk
psk=Sup3rD0nkey

[ipv4]
dns-search=
method=auto

[ipv6]
addr-gen-mode=stable-privacy
dns-search=
method=auto
root@sok-01:/etc/NetworkManager/system-connections#

Find

permissions=

Replace with

permissions=user:USER_NAME_HEARE:;

USER_NAME_HEARE = replace this with actual username, that need to edit the network configuration.

August 7, 2019

Change Linux user shell

To change shell for a user, run

chsh --shell PATH_TO_SHELL USERNAME

Example

chsh --shell /bin/bash okadmin

I will add a user, if no shell specified, it use sh as shell.

root@lab:~# useradd okadmin
root@lab:~# su - okadmin
No directory, logging in with HOME=/
$ echo $SHELL
/bin/sh
$ exit
root@lab:~# chsh --shell /bin/bash okadmin
root@lab:~# su - okadmin
No directory, logging in with HOME=/
okadmin@lab:/$ echo $SHELL
/bin/bash
okadmin@lab:/$ logout
root@lab:~#

You can find what shell you are using now with command

echo $SHELL

August 6, 2019

CentOS add IP Address
To add IP address on a Linux server, first find name of your network interface. This can be done with command
```
ip link
```
In most case, it can be enp3s0 or eth0, if you have more than one network card, this may be differnt, in such case, you need to identify which network interface you need to configure the the IP address .

Now create file
```
vi /etc/sysconfig/network-scripts/ifcfg-enp3s0:1
```
Here i used enp3s0 as network inferface name, replace it with whatever network interface name you use.

Add following content
```
DEVICE="enp3s0:1"
IPADDR=IP_ADDR_HERE
NETMASK=255.255.255.255
```
IP_ADDR_HERE = replace with the IP address you need to add.

enp3s0 = replace with actual network interface name.

Restart network service with command
```
systemctl restart network
```
If you need to add another IP, create file with name
```
INTERFACE_NAME:2
```
for example “enp3s0:2”, you need to use same alias name in DEVICE entry (first line) in the file.

Adding IP Range in CentOS 6
August 5, 2019

gonit golang replacement for monit

gonit is a replacent for monitoring software monit. monit was removed from Debian 10 due to security issues and the devloper will not provide a patch for the security vlunerabilty in time for Debian 10 release.

You can download gonit from

https://github.com/bitnami/gonit

root@ip-172-26-14-184:~# gonit status

Uptime                         22h5m41s
Last Check                     2019-08-05 08:23:57.612314368 +0000 UTC m=+79440.116643915
Next Check                     2019-08-05 08:25:57.612314368 +0000 UTC m=+79560.116643915
Pid                            3162
Pid File                       /var/run/gonit.pid
Control File                   /etc/gonit/gonitrc
Socket File                    /var/run/gonit.sock
Log File                       /var/log/gonit.log
Process 'apache'
  status                                        Running
  pid                                              2020
  uptime                                       22h5m41s
  monitoring status                           monitored

Process 'mysql'
  status                                        Running
  pid                                              1911
  uptime                                       22h5m41s
  monitoring status                           monitored

Process 'php-fpm'
  status                                        Running
  pid                                              2014
  uptime                                       22h5m41s
  monitoring status                           monitored


root@ip-172-26-14-184:~#

August 5, 2019

Check if you are using 32 or 64 bit Linux

To identify if you are using 32 bit or 64 bit Linux OS, run command arch.

boby@sok-01:~$ arch
x86_64
boby@sok-01:~$

You can also use uname command

boby@sok-01:~$ uname -i
x86_64
boby@sok-01:~$

Another way is to use hostnamectl command and look for “Architecture”.

boby@sok-01:~$ hostnamectl
   Static hostname: sok-01
         Icon name: computer-desktop
           Chassis: desktop
        Machine ID: 70486772aac1410c9a8031851ab60a0d
           Boot ID: 46ff31881cca4e7090edb35f2af89a4a
  Operating System: Ubuntu 18.04.2 LTS
            Kernel: Linux 4.15.0-55-generic
      Architecture: x86-64
boby@sok-01:~$

July 31, 2019

linux sound

aplay

sudo alsa force-reload

vi /etc/modprobe.d/alsa-base.conf

Show Sound Devices

boby@fwhlin:~$ cat /proc/asound/cards
 0 [Intel          ]: HDA-Intel - HDA Intel
                      HDA Intel at 0xfb9f8000 irq 75
 1 [HDMI           ]: HDA-Intel - HDA ATI HDMI
                      HDA ATI HDMI at 0xfbcfc000 irq 76
boby@fwhlin:~$

boby@boby-pc ~ $ cat /proc/asound/card0/codec* | grep Codec
Codec: Realtek ALC892
boby@boby-pc ~ $

boby@boby-pc ~ $ cat /proc/asound/card0/pcm0c/info
card: 0
device: 0
subdevice: 0
stream: CAPTURE
id: ALC892 Analog
name: ALC892 Analog
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 1
subdevices_avail: 1
boby@boby-pc ~ $

July 31, 2019

aplay

aplay is a command line sound player for ALSA soundcard driver.

To list all available sound devices, run

boby@sok-01:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Generic [HD-Audio Generic], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: Generic [HD-Audio Generic], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: Generic [HD-Audio Generic], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: Generic [HD-Audio Generic], device 9: HDMI 3 [HDMI 3]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: headset [Sennheiser USB headset], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: Generic_1 [HD-Audio Generic], device 0: ALC887-VD Analog [ALC887-VD Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 2: Generic_1 [HD-Audio Generic], device 1: ALC887-VD Digital [ALC887-VD Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
boby@sok-01:~$

July 31, 2019

Nginx vs Apache

I recently added nginx as front end for apache. Now nginx serve static content, PHP requests are peroxided to Apache.

Nginx frontend, Apache backend

[root@server12 ~]# ab -n 1000 -c 100 http://netfree.netfreehost.com/
This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright 2006 The Apache Software Foundation, http://www.apache.org/

Benchmarking netfree.netfreehost.com (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Finished 1000 requests


Server Software:        nginx/1.1.0
Server Hostname:        netfree.netfreehost.com
Server Port:            80

Document Path:          /
Document Length:        16844 bytes

Concurrency Level:      100
Time taken for tests:   5.463353 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      17357000 bytes
HTML transferred:       16844000 bytes
Requests per second:    183.04 [#/sec] (mean)
Time per request:       546.335 [ms] (mean)
Time per request:       5.463 [ms] (mean, across all concurrent requests)
Transfer rate:          3102.49 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.8      0       5
Processing:    44  518  93.9    534     719
Waiting:       44  517  94.0    533     718
Total:         47  518  93.2    534     719

Percentage of the requests served within a certain time (ms)
  50%    534
  66%    553
  75%    566
  80%    574
  90%    592
  95%    606
  98%    642
  99%    665
 100%    719 (longest request)
[root@server12 ~]#

Apache Only

[root@server12 ~]# ab -n 1000 -c 100 http://netfree.netfreehost.com:81/
This is ApacheBench, Version 2.0.40-dev <$Revision: 1.146 $> apache-2.0
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Copyright 2006 The Apache Software Foundation, http://www.apache.org/

Benchmarking netfree.netfreehost.com (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Finished 1000 requests


Server Software:        Apache/2.2.3
Server Hostname:        netfree.netfreehost.com
Server Port:            81

Document Path:          /
Document Length:        16844 bytes

Concurrency Level:      100
Time taken for tests:   7.102347 seconds
Complete requests:      1000
Failed requests:        1
   (Connect: 0, Length: 1, Exceptions: 0)
Write errors:           0
Total transferred:      17351384 bytes
HTML transferred:       16827683 bytes
Requests per second:    140.80 [#/sec] (mean)
Time per request:       710.235 [ms] (mean)
Time per request:       7.102 [ms] (mean, across all concurrent requests)
Transfer rate:          2385.69 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   1.1      0       6
Processing:    34  676 174.9    669    1261
Waiting:       32  675 175.0    668    1260
Total:         34  676 174.4    669    1261

Percentage of the requests served within a certain time (ms)
  50%    669
  66%    696
  75%    732
  80%    754
  90%    893
  95%    974
  98%   1081
  99%   1128
 100%   1261 (longest request)
[root@server12 ~]#

See Apache, Nginx

July 30, 2019

Git stdin is not a tty
When i push to get respo, i get error
```
stdin: is not a tty
```
Other than this error on push and pull, everything worked fine.

SOLUTION 1

Add following to top of file /home/git/.bashrc
```
if [ $(expr index "$-" i) -eq 0 ]; then
    return
fi
```
Modified .bashrc on my server
```
root@server70 [~]# cat /home/git/.bashrc
# .bashrc

if [ $(expr index "$-" i) -eq 0 ]; then
    return
fi

# Source global definitions
if [ -f /etc/bashrc ]; then
        . /etc/bashrc
fi

# User specific aliases and functions
root@server70 [~]#
```
SOLUTION 2

The problem is fixed by
```
cd /home/git
mv .bashrc .bashrc_old
```
This is caused on cpanel servers (i have installed gitosis on a cpanel less server a day before and it worked with out any error, this server have cpanel dns only installed.) as cpanel adds
```
mesg y
```
in file /etc/bashrc

It also adds
```
export EDITOR="pico"
export VISUAL="pico"
```
i replace it with following as i prefer vi
```
export EDITOR="vi"
export VISUAL="vi"
```
See Git
July 28, 2019

Category: Linux

Remote Desktop Software

Enable Remote Desktop

Show Sound Devices

Nginx frontend, Apache backend

Apache Only

SOLUTION 1

SOLUTION 2