Category: Linux

Apache AH00144: couldn’t grab the accept mutex

On Ubuntu 18.04 server, apache crashed. On checking apache error log, found following

[Mon Aug 13 23:19:24.625927 2018] [mpm_prefork:emerg] [pid 2378] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Mon Aug 13 23:19:24.626990 2018] [mpm_prefork:emerg] [pid 1227] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Mon Aug 13 23:19:24.628515 2018] [mpm_prefork:emerg] [pid 1211] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Mon Aug 13 23:19:24.628693 2018] [mpm_prefork:emerg] [pid 1309] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Mon Aug 13 23:19:24.629122 2018] [mpm_prefork:emerg] [pid 2387] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Mon Aug 13 23:19:24.629319 2018] [mpm_prefork:emerg] [pid 1603] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Mon Aug 13 23:19:24.629483 2018] [mpm_prefork:emerg] [pid 1637] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Mon Aug 13 23:19:24.629659 2018] [mpm_prefork:emerg] [pid 1566] (43)Identifier removed: AH00144: couldn't grab the accept mutex
[Mon Aug 13 23:19:25.366503 2018] [core:alert] [pid 990] AH00050: Child 1211 returned a Fatal error... Apache is exiting!
[Mon Aug 13 23:19:25.366568 2018] [:emerg] [pid 990] AH02818: MPM run failed, exiting

To fix the error, edit file

vi /etc/apache2/apache2.conf

Find

#Mutex file:${APACHE_LOCK_DIR} default

Replace with

Mutex posixsem

Restart Apache

service apache2 restart

See Apache

August 17, 2018

How to Block a Country in CSF firewall
To block all traffic from a country in CSF Firewall edit file /etc/csf/csf.conf
```
vi /etc/csf/csf.conf
```
Find the line
```
CC_DENY = ""
```
In this line, you can add 2 Letter country code. For example to block China and Russia, add
```
CC_DENY = "CN,RU"
```
Now you need to restart firewall with command
```
systemctl restart lfd
csf -r
```
August 14, 2018
How to view login history on Linux Server
To see login history on a Linux system, you can use the “last” command.
```
last
```
On the screenshot above, it shows “admin.serverok.i” for some of the logins. This is because DNS resolve is enabled in SSH configuration, so IP get converted to hostname and it get truncated. To see the full hostname, run
```
last -a
```
If you don’t want IP converted to hostname, run
```
last -ai
```
To list only the last 10 logins, run
```
last -n 10
```
-n 10 limit result to last 10 logins.

Login history is stored in the file
```
/var/log/wtmp
```
This file can grow and get rotated over time. If the file gets rotated, when you use the “last” command, it won’t report login history from older files.
```
root@server12:/var/log# ls -l | grep wtmp
-rw-rw-r-- 1 root  utmp   935K Aug  7 04:31 wtmp
-rw-rw-r-- 1 root  utmp   1.1M Jun  3  2017 wtmp-20170603
root@server12:/var/log# 
```
To see login history from an older file, you need to specify the location of the file using -f argument.
```
last -f /var/log/wtmp-20170603
```
You can also use the command
```
utmpdump /var/log/wtmp-20170603
```
To view the last 10 logins with full hostname from the old login file wtmp-20170603, use
```
last -n 10 -a -f /var/log/wtmp-20170603
```
The file name may differ in your server, check the /var/log folder for actual file names.

How to check old login history with last command
August 13, 2018
mysqldump
mysqldump is a command used to backup MySQL databases.

To take backup, run
```
mysqldump --opt DB_NAME > DB_NAME.sql
```
To backup with triggers, routines, and events
```
mysqldump --opt --triggers --routines --events --single-transaction DB_NAME > DB_NAME.sql
```
–opt combines many options. It is same as adding –add-drop-table, –add-locks, –create-options, –disable-keys, –extended-insert, –lock-tables, –quick, and –set-charset.

–extended-insert option will group together all INSERT operations for a table. This makes the backup file smaller and makes restoration faster. I restored a mysqldump bakcup, it take me 2 hours to restore. Same database backup with –extended-insert option take only 10 minutes to restore. If you want a separate INSERT for each row, then use –skip-extended-insert or –complete-insert option

Backup All Databases

To backup all databases, run
```
mysqldump --events --routines --triggers --all-databases | gzip -9 > "$(date +%F-%H%m%S)"-mysql-backup.sql.gz
```
To backup MySQL databases into separate files, run
```
mkdir /root/mysqlbackup/
for DB in $(mysql -Be "show databases" | grep -v 'row\|information_schema\|Database\|performance_schema') ; do
    mysqldump --opt --events --routines --triggers ${DB}  > /root/mysqlbackup/${DB}.sql
done
```
If you need to compress the sql file. use
```
mkdir /root/mysqlbackup/
for DB in $(mysql -Be "show databases" | grep -v 'row\|information_schema\|Database\|performance_schema') ; do
    mysqldump --skip-lock-tables --events --routines --triggers ${DB} | gzip -9 > /root/mysqlbackup/"$(date +%F-%H%m%S)"-${DB}.sql.gz
done
```
Backup Database Structure only
```
mysqldump --no-data DB_NAME > DB_NAME.sql
```
Backup Only routines
```
mysqldump --routines --no-create-info --no-data --no-create-db --skip-opt DB_NAME > DB_NAME-routines.sql
```
Related Posts
August 12, 2018
grep
To find a string inside files in a folder, use
```
grep -rnw ./ -e "STRING_TO_FIND"
```
Or
```
grep -irl "STRING_TO_FIND" ./
```
Or
```
grep -ir 'STRING_TO_FIND' ./ | cat
```
See ack better grep for programmers
August 12, 2018
Git

Monitor file changes in your Website
PHP Script to pull changes from GIT Repository
How to protect .git folder using htaccess
Git stdin is not a tty
Git Ignore file Permission (chmod)
Show git branch in terminal
Color git command line result
How to block .git directory in nginx
Find who added a file to git repo

Git Hooks

Auto push after git commit

Git Hosting

https://about.gitea.com
https://gitlab.com

August 9, 2018

Monitor file changes in your Website

This script can be used to notify you when a file changed in your website. This is useful when you want to know when a file changed or your site is hacked and you to monitor your site for file changes so you know when hacker upload or modify a file.

First you need to add your web site to GIT.

This can be with

cd /var/www/html
git init
git add .
git commit -a -m "inital commit"

Replace /var/www/html with actual DocumentRoot for your web site.

Every time you modify or add a file, you need to commit it to git you will get alerted. You can commit a new file to git with command

git add FILE_NAME
git commit -a

Create a file

mkdir /usr/serverok/
vi /usr/serverok/check-files.php

Add following content

In the script, replace /var/www/html with actual document root of your web site. Change email and site name with your email and domain name.

Set following cronjob.

0 * * * * /usr/bin/php /usr/serverok/check-files.php

Cronjob will run every 1 hour and email you if any file change is detected. You can modify cronjob if you want to monitor more frequently, every 1 hour will be fine for most uses.

If you have a folder or file that you need to ignore, you can create a file with name ".gitignore" and add path to file/folder in it, git will ignore files/folders listed in it.

August 9, 2018

Restart rsync on failure
When copying a large site form a shared server using rsync, the rsync process on get killed, this may be done by some program on shared host or server admin manually killing the process.

Here is a bash script that will check if rsync exited normally or not, then retry the trasfter is rsync failure detected.
```
#!/bin/bash

while [ 1 ]
do
    rsync -avzP [email protected]:/kunden/homepages/18/d686010467/htdocs/jobformazione/ /home/jobformazione/
    if [ "$?" = "0" ] ; then
        echo "rsync completed normally"
        exit
    else
        echo "Rsync failed. Retrying..."
        sleep 180
    fi
done
```
Save the file as 1.sh, then run it with
```
bash ./1.sh
```
You need to add servers SSH key in remote server so rsync work with out password.
August 7, 2018

iptv

https://xtream-codes.com/
https://www.infomir.eu/eng/solutions/ministra-tv-platform/
https://flussonic.com/flussonic-media-server
https://newiq.pl

Xtream Codes

DocumentRoot = /home/xtreamcodes/iptv_xtream_codes/wwwdir/ (this is accessable using URL http://IP_ADDR:25461/)

Client Area can be accessed with

http://IP_ADDR:25461/client_area/

Ports used = 25461 (nginx), 25462 (nginx_rtmp), 25463 (nginx)

root@ds11154:~# netstat -antp | grep LIST | grep ngin
tcp        0      0 0.0.0.0:31210           0.0.0.0:*               LISTEN      2012/nginx_rtmp 
tcp        0      0 0.0.0.0:25461           0.0.0.0:*               LISTEN      2015/nginx      
tcp        0      0 0.0.0.0:25462           0.0.0.0:*               LISTEN      2012/nginx_rtmp 
tcp        0      0 0.0.0.0:25463           0.0.0.0:*               LISTEN      2015/nginx      
root@ds11154:~#

Some useful commands/config

/home/xtreamcodes/iptv_xtream_codes/nginx/conf/nginx.conf
/home/xtreamcodes/iptv_xtream_codes/start_services.sh
/home/xtreamcodes/iptv_xtream_codes/nginx/sbin/nginx -s reload
/home/xtreamcodes/iptv_xtream_codes/wwwdir/
/home/xtreamcodes/iptv_xtream_codes/php/etc

ffmpeg command used to streaming video

/home/xtreamcodes/iptv_xtream_codes/bin/ffmpeg -y -nostdin -hide_banner -loglevel warning -err_detect ignore_err -user-agent Xtream-Codes IPTV Panel Pro -nofix_dts -start_at_zero -copyts -vsync 0 -correct_ts_overflow 0 -avoid_negative_ts disabled -max_interleave_delta 0 -probesize 5000000 -analyzeduration 5000000 -progress http://127.0.0.1:9000/progress.php?stream_id=124 -i http://da1981.xyz:8080/tJvIus0CY5/XwRjNIiKZM/8583 -vcodec copy -scodec copy -acodec copy -individual_header_trailer 0 -f segment -segment_format mpegts -segment_time 10 -segment_list_size 6 -segment_format_options mpegts_flags=+initial_discontinuity:mpegts_copyts=1 -segment_list_type m3u8 -segment_list_flags +live+delete -segment_list /home/xtreamcodes/iptv_xtream_codes/streams/124_.m3u8 /home/xtreamcodes/iptv_xtream_codes/streams/124_%d.ts

July 30, 2018

How to extract RAR file in Linux
unar is a utility to extract rar archive files.

Using unrar

To extract a rar file, run
```
unrar x filename.rar
```
Install unare on Ubuntu/Debian

To install unrar on Ubuntu/Debian, run
```
apt install unrar -y
```
Install Unrar from source

Download unrar from

http://www.rarlab.com/download.htm
```
cd /usr/local/src
wget https://www.rarlab.com/rar/rarlinux-x64-6.0.b1.tar.gz
tar zxvf rarlinux-x64-6.0.b1.tar.gz
cd rar
cp rar unrar /usr/bin
```
July 29, 2018

Start meguca on boot

Meguca is an open source annonymouse imageboard written in Go Lang and Node.js

https://github.com/bakape/meguca

To start Meguca on boot, you can use monit

Create a monitoring script with

check process meguca with pidfile /meguca/.pid
  start program = "/bin/su -c 'cd /meguca; ./meguca start' meguca"
  stop program  = "/bin/su -c 'cd /meguca; ./meguca stop' meguca"

if failed port 8000 protocol HTTP
  request /api/health-check
  with timeout 10 seconds
  then restart

/meduca is where Meguca is installed.

Create a config.json file with

vi /meguca/config.json

Add following content

{
	"ssl": false,
	"reverseProxied": true,
	"gzip": false,
	"imagerMode": 0,
	"cacheSize": 128,
	"address": "127.0.0.1:8000",
	"database": "user=meguca password=meguca dbname=meguca sslmode=disable",
	"certPath": "",
	"reverseProxyIP": ""
}

reverseProxied is set to true because my installation is behind reverse proxy (CloudFlare).

Make changes to config settings as requires.

Create a user

useradd -m -s /bin/bash meguca

Change ownership of meguca files

chown -R meguca:meguca /meguca

July 22, 2018

NameServer
Verify if a name server is registered with
```
whois -h whois.verisign-grs.com "nameserver=ns20.hostonnet.com"
```
Find all sites using a specific nameserver

Change Nameservers
Create Custom Nameservers
July 21, 2018

Category: Linux

Backup All Databases

Backup Database Structure only

Backup Only routines

Related Posts

Git Hooks

Git Hosting

Using unrar

Install unare on Ubuntu/Debian

Install Unrar from source

Change Nameservers

Create Custom Nameservers