Tag: linux

Make hosts file editable with out sudo
hosts file allow you to override DNS. This will allow you to point a domain to difernt IP address on your computer. It is helpful for testing sites during site migrations.

If you edit hosts file a lot, it is better to make it owned by you or make it editable by everyone.
```
sudo chmod 777 /etc/hosts
```
Now onwards, you can edit the file with out sudo requirment.

Another option is make it owned by current user.
```
sudo chown USER_HERE:GROUP_HERE /etc/hosts
```
See /etc/hosts
October 11, 2020
Creating Software RAID 5
RAID 5 Requires 3 or more physical disks. It provides the redundancy of RAID 1 combined with the speed and size benefits of RAID 0. RAID 5 uses striping, like RAID 0, but also stores parity blocks distributed across each member disk. In the event of a failed disk, these parity blocks are used to reconstruct the data on a replacement disk. RAID 5 can withstand the loss of one member disk.

I have a server with 4 * 4 TB Disks. Here is parted -l result on the server.

On this server /dev/sda, /dev/sdb, /dev/sdc and /dev/sdd are 4 TB disks and are not in use. Lets format these disk to be used as RAID 5.

Following commands need to be executed for each of the disks.
```
parted -a optimal /dev/sda
mklabel gpt
mkpart primary ext4 0% 100%
set 1 raid on
align-check optimal 1
print
quit
```
This will partition the disks, set file system as raid.

Repeat the steps for /dev/sdb, /dev/sdc and /dev/sdd.

Now you have all disks formatted, ready to be used in raid array.

Create RAID 5 array with command
```
mdadm --create --verbose --level=5 --chunk=64 --raid-devices=4 --layout=left-symmetric /dev/md0 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1
```
Once raid created, you can see status with command
```
cat /proc/mdstat
```
Before we can use raid array, we need to create a file system on the raid with command
```
mkfs.ext4 /dev/md0
```
Create mdadm.conf file with following command
```
mkdir /etc/mdadm/
cat /etc/mdadm/mdadm.conf
mdadm --detail --scan >> /etc/mdadm/mdadm.conf
cat /etc/mdadm/mdadm.conf
```
Mount Raid 5 Array

I want to mount the new raid 5 array as /home. For this i edited /etc/fstab, added
```
/dev/md0        /home           ext4    errors=remount-ro 0       1
```
After rebooting, i have 11 TB RAID 5 drive mounted as /home
October 10, 2020
How to increase /tmp partition size
On a Linux server /tmp partition was only 1 GB, it get full at times.

Server had following in its /etc/fstab file
```
[root@imeicheck-2020 ~]# cat /etc/fstab 
UUID=c0f46bb1-c0bc-4199-95d6-551d03c12a0a /                       xfs     defaults        1 1
/var/.tempdisk /tmp ext4 loop,rw,noexec,nosuid,nodev,nofail 0 0
/tmp /var/tmp none bind 0 0
[root@imeicheck-2020 ~]#
```
Currenly file /var/.tempdisk is mounted as /tmp.

So i created a new file with 4 GB size
```
dd if=/dev/zero of=/var/sok_tmp bs=1M count=4096
```
Format it as ext4 file system
```
mkfs -t ext4 /var/sok_tmp
```
Before i swith /tmp to newly created disk, i need to copy content of current /tmp to it. For this i mount the new disk as /tmp2
```
mkdir /tmp2
mount -o loop /var/sok_tmp /tmp2
rsync -avzP /tmp/ /tmp2/
```
Now you have all files of /tmp in /tmp2, edit /etc/fstab
```
vi /etc/fstab
```
Find entry for current /tmp partition
```
/var/.tempdisk /tmp ext4 loop,rw,noexec,nosuid,nodev,nofail 0 0
```
Replace it with new file you created
```
/var/sok_tmp /tmp ext4 loop,rw,noexec,nosuid,nodev,nofail 0 0
```
Reboot the server. You will have 4 GB /tmp partition now.
September 28, 2020
Lock User Account in Linux
To lock a Linux User account, run
```
usermod -L USER_NAME_HERE
```
You can verify the account is locked with command
```
passwd --status USER_NAME_HERE
```
Example

See usermod
September 24, 2020
Find limit search depth
I wanted to find some files inside the subdirectory of the current folder. To do this, find have maxdepth option.
```
find ./ -maxdepth 2 -name '*.gz'
```
This command will limit search depth to the current directory and all first-level sub folders.

See find
September 2, 2020

Set vim as default cronjob editor

Method 1

vi /etc/bashrc

Find

export EDITOR="pico"
export VISUAL="pico"

Replace with

export EDITOR="vi"
export VISUAL="vi"

Method 2

edit .bash_profile

vi /root/.bash_profile

Add

export VISUAL=vi

Once added, .bash_profile will look like

root@server54 [~]# cat .bash_profile
# .bash_profile

# Get the aliases and functions
if [ -f ~/.bashrc ]; then
        . ~/.bashrc
fi

# User specific environment and startup programs

PATH=$PATH:$HOME/bin

export VISUAL=vi
export PATH
unset USERNAME
uptime
root@server54 [~]#

Method 3

If you need it done one time only, run following commands on command prompt.

VISUAL=vi; export VISUAL

August 30, 2020

brctl show

[root@server70 etc]# brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.002590d08d66       no              eth0
                                                        vnet0
virbr0          8000.525400f12faf       yes             virbr0-nic
[root@server70 etc]# ifconfig
br0       Link encap:Ethernet  HWaddr 00:25:90:D0:8D:66
          inet addr:192.99.18.195  Bcast:192.99.18.255  Mask:255.255.255.0
          inet6 addr: fe80::225:90ff:fed0:8d66/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8108397 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7823258 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1951542690 (1.8 GiB)  TX bytes:15136345174 (14.0 GiB)

br0:1     Link encap:Ethernet  HWaddr 00:25:90:D0:8D:66
          inet addr:198.27.105.228  Bcast:198.27.105.228  Mask:255.255.255.255
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0      Link encap:Ethernet  HWaddr 00:25:90:D0:8D:66
          inet6 addr: fe80::225:90ff:fed0:8d66/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:69612987 errors:6 dropped:0 overruns:0 frame:6
          TX packets:114006505 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:7042298846 (6.5 GiB)  TX bytes:151793078797 (141.3 GiB)
          Interrupt:48 Memory:fe9e0000-fea00000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:407995 errors:0 dropped:0 overruns:0 frame:0
          TX packets:407995 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1284505268 (1.1 GiB)  TX bytes:1284505268 (1.1 GiB)

virbr0    Link encap:Ethernet  HWaddr 52:54:00:F1:2F:AF
          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

vnet0     Link encap:Ethernet  HWaddr FE:54:00:F6:41:4B
          inet6 addr: fe80::fc54:ff:fef6:414b/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:44 errors:0 dropped:0 overruns:0 frame:0
          TX packets:24993 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:3499 (3.4 KiB)  TX bytes:2333834 (2.2 MiB)

[root@server70 etc]#

brctl showmacs br0

[root@server70 etc]#  brctl showmacs br0
port no mac addr                is local?       ageing timer
  1     00:05:73:a0:00:00       no                11.10
  1     00:07:b4:00:00:02       no                 2.72
  1     00:07:b4:00:01:01       no                 4.73
  1     00:07:b4:00:01:02       no                 6.65
  1     00:25:90:7b:a3:8e       no                31.80
  1     00:25:90:7c:72:34       no                53.08
  1     00:25:90:d0:8d:66       yes                0.00
  1     00:2a:6a:3d:50:81       no               119.90
  1     00:2a:6a:3d:df:bc       no                 2.33
  1     c8:f9:f9:58:3f:c0       no                 0.00
  1     d8:24:bd:91:c7:00       no                 0.00
  2     fe:54:00:f6:41:4b       yes                0.00
[root@server70 etc]#

brctl showstp br0

[root@server70 etc]# brctl showstp br0
br0
 bridge id              8000.002590d08d66
 designated root        8000.002590d08d66
 root port                 0                    path cost                  0
 max age                  19.99                 bridge max age            19.99
 hello time                1.99                 bridge hello time          1.99
 forward delay            14.99                 bridge forward delay      14.99
 ageing time             299.95
 hello timer               0.42                 tcn timer                  0.00
 topology change timer     0.00                 gc timer                   8.42
 hash elasticity           4                    hash max                 512
 mc last member count      2                    mc init query count        2
 mc router                 1                    mc snooping                1
 mc last member timer      0.99                 mc membership timer      259.96
 mc querier timer        254.96                 mc query interval        124.98
 mc response interval      9.99                 mc init query interval    31.24
 flags


eth0 (0)
 port id                0000                    state                forwarding
 designated root        8000.002590d08d66       path cost                  4
 designated bridge      8000.002590d08d66       message age timer          0.00
 designated port        8001                    forward delay timer        0.00
 designated cost           0                    hold timer                 0.00
 mc router                 1
 flags

vnet0 (0)
 port id                0000                    state                forwarding
 designated root        8000.002590d08d66       path cost                100
 designated bridge      8000.002590d08d66       message age timer          0.00
 designated port        8002                    forward delay timer        0.00
 designated cost           0                    hold timer                 0.00
 mc router                 1
 flags

[root@server70 etc]#

August 30, 2020

Block Country in CSF firewall
CSF firewall can block all traffic from a country or list of countries using the GeoIP database.

To block a country, edit the file
```
/etc/csf/csf.conf
```
Find
```
CC_DENY=""
```
Replace with
```
CC_DENY="2_LETTER_COUNTRY_CODE"
```
Here is an example to block all traffic from China
```
CC_DENY="CN"
```
If you want to block another country, you can add it like
```
CC_DENY="CN,RU"
```
Now restart CSF firewall with
```
csf -r
```
See CSF firewall
August 30, 2020

Can’t locate version.pm in @INC

I got error “Can’t locate version.pm in @INC” running awk.

[root@vmi431969 /]# ack mp3pdjSu5B0
Can't locate version.pm in @INC (@INC contains: /usr/local/lib64/perl5 /usr/local/share/perl5 /usr/lib64/perl5/vendor_perl /usr/share/perl5/vendor_perl /usr/lib64/perl5 /usr/share/perl5 .) at /usr/local/bin/ack line 18.
BEGIN failed--compilation aborted at /usr/local/bin/ack line 18.
[root@vmi431969 /]#

On CentOS, this error is fixed by running

yum install perl-version.x86_64 -y

See Errors

August 21, 2020

Plesk Mail not working amavis error

When sending email from a Plesk server, i get error

Aug 11 19:49:28 vmi274961 postfix/smtp[29276]: E413C3320265: to=, relay=none, delay=0.47, delays=0.47/0/0/0, dsn=4.4.1, status=deferred (connect to 127.0.0.1[127.0.0.1]:10024: Connection refused)

This is beccause amavis service is not running. It is supposed to be run in port 10024

When i try to start amavis service, i get error

Aug 17 09:31:04 server.ishiply.com systemd[1]: Starting LSB: Starts amavisd-new mailfilter...
Aug 17 09:31:05 server.ishiply.com amavis[7771]: Starting amavisd: Problem in Amavis SQL base code: Can't locate DBI.pm in @INC (you may need to install the DBI module) (@INC contains: /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.22.1 /usr/local/share/perl/5.22.1 /usr/lib/x86_64-linux-gnu/perl5/5.22 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.22 /usr/share/perl/5.22 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base) at (eval 100) line 19.
Aug 17 09:31:05 server.ishiply.com amavis[7771]: BEGIN failed--compilation aborted at (eval 100) line 19.
Aug 17 09:31:05 server.ishiply.com amavis[7771]: (failed).

This is becuase Perl DBI module was missing. On Ubuntu server, i found the package that provide this DBI.pm with command “apt-cache search DBI.pm”. To fix the error, install package libdbd-mysql-perl.

apt install -y libdbd-mysql-perl

After installing this, i try start amavis again. I got differnt error

root@server:~# systemctl status amavis.service
● amavis.service - LSB: Starts amavisd-new mailfilter
   Loaded: loaded (/etc/init.d/amavis; bad; vendor preset: enabled)
   Active: failed (Result: exit-code) since Mon 2020-08-17 09:59:37 SAST; 5s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 10597 ExecStart=/etc/init.d/amavis start (code=exited, status=1/FAILURE)

Aug 17 09:59:36 server.ishiply.com systemd[1]: Starting LSB: Starts amavisd-new mailfilter...
Aug 17 09:59:37 server.ishiply.com amavis[10603]: starting. /usr/sbin/amavisd-new at server.ishiply.com amavisd-new-2.10.1 (20141025), Unicode aware, LC_ALL="C", LANG="en_US.UTF-8"
Aug 17 09:59:37 server.ishiply.com amavis[10597]: Starting amavisd: ERROR: MISSING REQUIRED ADDITIONAL MODULES:
Aug 17 09:59:37 server.ishiply.com amavis[10597]:   DBD::mysql
Aug 17 09:59:37 server.ishiply.com amavis[10597]:   DBD::mysql
Aug 17 09:59:37 server.ishiply.com amavis[10597]: (failed).
Aug 17 09:59:37 server.ishiply.com systemd[1]: amavis.service: Control process exited, code=exited status=1
Aug 17 09:59:37 server.ishiply.com systemd[1]: Failed to start LSB: Starts amavisd-new mailfilter.
Aug 17 09:59:37 server.ishiply.com systemd[1]: amavis.service: Unit entered failed state.
Aug 17 09:59:37 server.ishiply.com systemd[1]: amavis.service: Failed with result 'exit-code'.
root@server:~#

To find package that provide DBD::mysql, i used command

apt-cache search DBD::mysql

To fix, install the package

apt install -y libdbd-mysql-perl

I am able to start amavis service with command

systemctl start amavis.service

In Plesk > Extensions > Plesk Email Security now shows Amavis, Postfix and Dovecot running properly.

August 17, 2020

Install elasticsearch on CentOS 7

To install elasticsearch, first install java

yum -y install java-1.8.0-openjdk

Import key

rpm --import https://artifacts.elastic.co/GPG-KEY-elasticsearch

Create file

vi /etc/yum.repos.d/elasticsearch.repo

Paste following

[elasticsearch]
name=Elasticsearch repository for 7.x packages
baseurl=https://artifacts.elastic.co/packages/7.x/yum
gpgcheck=1
gpgkey=https://artifacts.elastic.co/GPG-KEY-elasticsearch
enabled=0
autorefresh=1
type=rpm-md

Install elasticsearch

yum install --enablerepo=elasticsearch elasticsearch

Set elastic search to start on boot

systemctl enable elasticsearch

To start/stop/status

systemctl stop elasticsearch.service
systemctl start elasticsearch.service
systemctl status elasticsearch.service

To see logs

tail -f /var/log/elasticsearch/elasticsearch.log

ElasticSearch runs on port 9200

[root@server ~]# netstat -lntp | grep java
tcp6       0      0 127.0.0.1:9200          :::*                    LISTEN      1289/java           
tcp6       0      0 ::1:9200                :::*                    LISTEN      1289/java           
tcp6       0      0 127.0.0.1:9300          :::*                    LISTEN      1289/java           
tcp6       0      0 ::1:9300                :::*                    LISTEN      1289/java           
[root@server ~]#

If you get error starting elasticsearch, check Elasticsearch failed to start on CentOS 7

If you have a previous installation, make sure you delete left over files before you install differnt version of elasticsearch. I removed following files/folders when i had to downgrade elasticsearch.

/etc/sysconfig/elasticsearch.rpmsave
/var/lib/elasticsearch
/var/log/elasticsearch

See elasticsearch

August 15, 2020