Tag: linux

Allow SSH root login
To allow SSH login as user root, edit file
```
vi /etc/ssh/sshd_config
```
Find
```
PermitRootLogin no
```
Replace with
```
PermitRootLogin yes
```
restart sshd.
```
systemctl restart sshd
```
July 23, 2019

Adding a group in Linux with addgroup

addgroup linux commanhd allow you to create a group.

addgroup [options] [--gid ID] group

Example

root@ok:~# addgroup sokadmin
Adding group `sokadmin' (GID 1004) ...
Done.
root@ok:~#

Add a system group (normally group id below 500, run

addgroup --system [options] [--gid ID] group

July 23, 2019

PCI COMPLIANCE SSH Diffie-Hellman Modulus

When doing PCI COMPLIANCE scan got error related to SSH Diffie-Hellman Modulus <= 1024 Bits (Logjam). SSH Diffie-Hellman Modulus error

To fix the error, run

cp /etc/ssh/moduli /etc/ssh/moduli.backup
awk '$5 > 2000' /etc/ssh/moduli > /etc/ssh/moduli

Edit file

vi /etc/ssh/sshd_config

Add at end of the file

KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256

Restart sshd

systemctl restart sshd

July 21, 2019

locate command on Linux
locate command find files on a linux server.

To install locate, run

On CentOS
```
yum install mlocate
```
On Debian/Ubuntu
```
apt install mlocate
```
locate searches through a static index of files. This is rebuild daily using cronjob. You can manually update it by running
```
updatedb
```
July 21, 2019
ack better grep for programmers
ack is a tool like grep optimized for programmers.

ack show the matched files name only

On Debian/Ubuntu, you can install it with apt
```
apt install ack
```
To install from source, run
```
curl https://beyondgrep.com/ack-v3.0.2 > /usr/local/bin/ack && chmod 0755 /usr/local/bin/ack
```
For installing for just one user, run
```
curl https://beyondgrep.com/ack-v3.0.2 > ~/bin/ack && chmod 0755 ~/bin/ack
```
On RHEL/CentOS, you may need to install dependency
```
yum install perl-version
```
For the latest version, always check

https://beyondgrep.com/install/

See grep
July 21, 2019
log
Logging Linux Commands for all users
Monitor Apache site traffic with Apachetop
Find IP with Most Access from Apache Log
Apache LogFormat show full domain name
Display real time statistics with Logtop
Cpanel find recently logged in users
How to get list of User-Agent from access log

Find the most requested pages
```
awk '{print $7}' access_log.log | sort | uniq -c | sort -nr
awk '{print $7}' access_log.log | sort | uniq -c | sort -nr | head -n 10
```
To view the most used User Agents
```
cat access_log.log |   awk -F\" '{print $6}' | sort | uniq -c | sort -nr | head -n 10
```
July 20, 2019
Monitor Apache site traffic with Apachetop
apachetop is a command line tool like top, that shows traffic on a web site. It used apache access log to show th stats. This will be useful to monitor a web sites traffic in real time.
```
cd /usr/local/src
wget https://github.com/HostOnNet/apachetop/archive/master.zip
unzip master.zip
cd apachetop-master
./configure --with-logfile=/var/log/httpd/access_log
make
make install
```
If you need to set path to apache log file, configure with
```
./configure --with-logfile=/path/to/apache/log/file.log
```
On CentOS
```
yum install apachetop
```
On Ubuntu/Debian
```
apt install apachetop
```
Running apachetop with custom log file location
```
apachetop -f /path/to/apache/log/file.log
```
July 20, 2019
Resize a linux file system with resize2fs
On cloud servers, once you upgrade disk, you will need to resize the filesystem. On Linux ext4 file system, you can do this with command resize2fs.

To resize filesystem on /dev/sdb, run
```
root@leonestage:~# resize2fs /dev/sdb
resize2fs 1.44.1 (24-Mar-2018)
Filesystem at /dev/sdb is mounted on /mnt/HC_Volume_2899894; on-line resizing required
old_desc_blocks = 2, new_desc_blocks = 3
The filesystem on /dev/sdb is now 10485760 (4k) blocks long.

root@leonestage:~#
```
Here the full disk is used as file system with NO partition. If you have partion, you need to specify partition number like /dev/sdb1
July 19, 2019
Plesk move vhosts folder
Plesk use /var/www/vhosts folder to store sites. On some servers this folder will be on smaller partition. Say you have all disk space on partition /home, in such cause, you can use following command to move web site files to /home folder with following command.
```
plesk bin transvhosts.pl --dest-dir /home/ --correct-scripts
```
/home/ = you can replace this any any folder you wish. Plesk will move the site files, update the configuration as required.

NOTE: In this example, i used /var/www/vhosts instead of /home/ as the server was using non default folder for vhosts, i am moving all sites back to default location (/var/www/vhosts).

See Plesk
July 19, 2019
Bandwidth Limit on rsync
I wanted to transfer some files between two computers, but don’t want to use all bandwidth available on the network as it will affect other users on the network.

To limit bandwidth, use –bwlimit Option.
```
rsync -avzP  --bwlimit=1500 /mnt/data/learn/css/BootStrap3/ [email protected]:/home/php-tutorial/BootStrap3/
```
Here –bwlimit=1500 will limit bandwidth usage to 1.5 MB/s.

See rsync
July 19, 2019

Redirect a site to HTTPS using PHP

This PHP script will redirect website visitors to HTTPS (SSL) URL. You can add this in your index.php of the website

if (empty($_SERVER['HTTPS']) || $_SERVER['HTTPS'] != "on" ) {
    header("HTTP/1.1 301 Moved Permanently");
    $newUrl = "https://" . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];
    Header("Location: $newUrl");
    exit;
}

To redirect visitors to a new URL using PHP, use the following PHP code

$newUrl = "https://NEW-URL-HERE" . $_SERVER['REQUEST_URI'];
header("HTTP/1.1 301 Moved Permanently");
Header("Location: $newUrl");
exit;

You can also use Apache mod_rewrite .htacess to do the redirection.

July 18, 2019

Install x11vnc on Ubuntu
To install x11vnc on Debian/Ubuntu, run
```
apt install -y x11vnc
```
To start vnc server, run
```
x11vnc -display :0
```
By default, there will be no password. To set password, run
```
x11vnc -storepasswd
```
To start x11vnc server with password, run
```
x11vnc -rfbauth ~/.vnc/passwd
```
July 17, 2019

Tag: linux

On CentOS

On Ubuntu/Debian

Running apachetop with custom log file location