Category: Linux

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
Linux Commands
General
- arch
- chsh – Change Linux user shell
- apropos
- whois
- uname
- chown
- at
- lynx
- setfacl
- tr
- gifsicle
- chattr
- chmod
System

strace
lsof
lspci

Networking

nmtui – configure networking

Disk/Storage

blkid – show UUID for disks.
vgcreate

Load
- vmstat
- atop
- top
July 28, 2019

strace: command not found

# strace -p 17723
-bash: strace: command not found
#

This is because strace not installed on the server. Install it with yum

# yum install strace
Loading "installonlyn" plugin
Setting up Install Process
Setting up repositories
Reading repository metadata in from local files
Parsing package install arguments
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Downloading header for strace to pack into transaction set.
strace-4.5.16-1.el5.1.i38 100% |=========================|  15 kB    00:00
---> Package strace.i386 0:4.5.16-1.el5.1 set to be updated
--> Running transaction check

Dependencies Resolved

=============================================================================
 Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
 strace                  i386       4.5.16-1.el5.1   base              163 k

Transaction Summary
=============================================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)

Total download size: 163 k
Is this ok [y/N]: y
Downloading Packages:
(1/1): strace-4.5.16-1.el 100% |=========================| 163 kB    00:00
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing: strace                       ######################### [1/1]

Installed: strace.i386 0:4.5.16-1.el5.1
Complete!
#

July 28, 2019

strace
strace command is used to trace system calls. This is useful to see what a process is doing.

To see what a process doing, run
```
strace -p PID_HERE
```
To run a command and strace
```
strace cat 1.txt
```
Debug apache start up
```
strace -Ff -o output.txt -e open /etc/init.d/httpd restart
cat output.txt | grep '= -1'
```
log strace out put to a file when running a command
```
strace -f -o debug.log npm install
```
July 28, 2019
MariaDB

MariaDB Repository Setup Script
MariaDB DEFAULT NULL ERROR 1064 (42000)
Install MariaDB 10.3 on CentOS 7

July 27, 2019

MariaDB Repository Setup Script

This script configure MariaDB repository on your server. You can find more details on offical page

https://mariadb.com/kb/en/library/mariadb-package-repository-setup-and-usage/

To setup mariadb repo, run

curl -sS https://downloads.mariadb.com/MariaDB/mariadb_repo_setup | sudo bash

I was expecting it ask me what version of MariaDB i like to setup. But it just setup MariaDB 10.4. I wanted to upgrade MariaDB to version 10.2, anyway i did upgrade to 10.4 and everything worked fine.

If you need a speicfic version, you can run like

curl -sS https://downloads.mariadb.com/MariaDB/mariadb_repo_setup | sudo bash -s -- --mariadb-server-version="mariadb-10.3"

Availabe versions are

mariadb-5.5
mariadb-10.0
mariadb-10.1
mariadb-10.2
mariadb-10.3
mariadb-10.4

When i run the script on Debian 9 server, i get following error

root@server:~# curl -sS https://downloads.mariadb.com/MariaDB/mariadb_repo_setup | sudo bash
[info] Repository file successfully written to /etc/apt/sources.list.d/mariadb.list
[info] Adding trusted package signing keys...
Executing: /tmp/apt-key-gpghome.TKjSzTY6ww/gpg.1.sh --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0x8167EE24 0xE3C94F49 0xcbcb082a1bb943db 0xF1656F24C74CD1D8 0x135659e928c12247
gpg: failed to start the dirmngr '/usr/bin/dirmngr': No such file or directory
gpg: connecting dirmngr at '/run/user/0/gnupg/d.3y8gtbm7kaj8h4royj6yoyug/S.dirmngr' failed: No such file or directory
gpg: keyserver receive failed: No dirmngr
[error] Failed to add trusted package signing keys.
root@server:~#

This is fixed by running

apt -y install dirmngr

July 27, 2019

Enable Remote Desktop in Ubuntu 18.04

To enable remote desktop on Ubuntu 18.04 (works with newer Ubuntu versions), go to settings.

Click on Sharing

Click on ON/OFF button on title bar to enable Desktop Sharing. Once enabled, click on “Screen Sharing” to See Desktop sharing option, you need to enable it for network connection.

Ubuntu use vino package to allow remote desktop over VNC.

See Ubuntu, VNC, remote desktop

July 27, 2019
Install iftop from source on CentOS
iftop allow you to monitor network traffic like top command. You can download iftop source from

http://www.ex-parrot.com/~pdw/iftop/

Before installing, install required packages
```
yum -y install libpcap libpcap-devel
```
To install iftop, run
```
cd /usr/local/src
wget http://www.ex-parrot.com/~pdw/iftop/download/iftop-0.17.tar.gz
tar xvf iftop-0.17.tar.gz
cd iftop-0.17
./configure --prefix=/usr/local
make
make install
```
To run iftop, type
```
iftop
```
See iftop
July 26, 2019
configure: error: can’t find pcap.h
When installing a software from source, i get error
```
configure: error: can't find pcap.h
  You're not going to get very far without libpcap.
```
To fix this on CentOS 7 server, run
```
yum -y install libpcap libpcap-devel
```
July 26, 2019

Linux add a user to group with adduser

adduser command like useradd, used to add a user to linux server.

adduser is more interactive, while useradd require all options passed using command line options.

 adduser  [options]  [--home  DIR]  [--shell  SHELL] [--no-create-home] [--uid ID] [--firstuid ID] [--lastuid ID] [--ingroup GROUP | --gid ID] [--disabled-password] [--disabled-login] [--gecos GECOS] [--add_extra_groups] user

For creating system user, run

adduser --system [options] [--home DIR] [--shell SHELL] [--no-create-home] [--uid ID] [--group | --ingroup GROUP | --gid ID] [--disabled-password] [--disabled-login] [--gecos GECOS] user

To add a user, run

useradd USERNAME_HERE

To delete a user, run

deladd USERNAME_HERE

July 24, 2019

Scan a folder with clamscan
To scan a folder, run
```
clamscan -r /path/to/folder/
```
-r will scan sub folders too.

To Scan a Folder (Only Show Infected)
```
clamscan -ri /path/to/folder/
```
To exclude a folder from search, use
```
clamscan -ri --exclude-dir="^/opt/zimbra/store" /opt/zimbra/
```
See clamav
July 23, 2019

Category: Linux

Nginx frontend, Apache backend

Apache Only

SOLUTION 1

SOLUTION 2

General

System

Networking

Disk/Storage

Load