I noticed once in Ubuntu Server 14.04 LTS configured as a router, in the file /var/log/kern.log the following error:Continue reading “How to fix the error “nf_conntrack: table full, dropping package””
wait_timeout – The number of seconds that the server waits for activity in a non-interactive connection before closing it.
At the time of connection, wait_timeout is taken from the global value wait_timeout or interactive_timeout depending on the client type (as defined by the CLIENT_INTERACTIVE connect option for mysql_real_connect ())
Connect to MySQL and see the current value:
mysql -u USER -p show variables like "wait_timeout"; show variables like "interactive_timeout"; quit;
By default, the values wait_timeout and interactive_timeout are 28800 seconds = 8 hours.
You can set minimum 1, maximum – 31536000, maximum (for Windows) – 2147483.
You can change the value of wait_timeout by executing the SQL query, for example:
set global wait_timeout = 28800; set global interactive_timeout = 28800;
That the set value has not been reset, it needs to be specified in the file /etc/mysql/my.cnf, in the mysqld block:
[mysqld] wait_timeout = 28800 interactive_timeout = 28800
Redmine – server web application for managing projects and tasks.
On the test I will install Redmine in Ubuntu Server 16.04, MySQL will be used as the database, and so first we will install the necessary components:
sudo apt-get update sudo apt-get install apache2 libapache2-mod-passenger sudo apt-get install mysql-server mysql-client
Now perform the installation of Redmine:
sudo apt-get install redmine redmine-mysql
Check whether bundler gem is installed:
sudo gem update sudo gem install bundler
Open the configuration file in the text editor passenger.conf:
sudo nano /etc/apache2/mods-available/passenger.conf
And after the line:
Create a symbolic link to Redmine in the web server directory:
sudo ln -s /usr/share/redmine/public /var/www/html/redmine
Open the web server configuration file in a text editor:
sudo nano /etc/apache2/sites-available/000-default.conf
And somewhere inside the VirtualHost block, we add:
<Directory /var/www/html/redmine> RailsBaseURI /redmine PassengerResolveSymlinksInDocumentRoot on </Directory>
Create a Gemfile.lock file and assign it to the owner of the web-server user www-data:
sudo touch /usr/share/redmine/Gemfile.lock sudo chown www-data:www-data /usr/share/redmine/Gemfile.lock
Restart the web server to apply all the changes:
sudo service apache2 restart
Now Redmine is installed and it can be opened by link http://HOST/redmine
Where it is necessary to press Enter, enter the standard login admin and password admin.
Let’s connect to the Asterisk console:
sudo asterisk -rvv
Let’s see what modules are already in use:
Files of modules with the extension * .so are in the directory /usr/lib/asterisk/modules/
To load and unload a module, commands are used (the module name is specified without a file extension, for example, not chan_sip.so, but chan_sip):
module load NAME module unload NAME
In order for the necessary modules to be loaded automatically when starting Asterisk, they must be specified in the file /etc/asterisk/modules.conf, for example, open it in the text editor nano:
sudo nano /etc/asterisk/modules.conf
You can enable the autoloading of all existing modules in the folder /usr/lib/asterisk/modules/:
And then we can exclude unnecessary ones using the following commands:
noload => module.so
Either prohibit downloading all and specify only those that are needed, for example:
;SIP VoIP driver load => chan_sip.so load => res_rtp_asterisk.so load => app_dial.so load => bridge_simple.so load => res_features.so load => res_musiconhold.so load => res_adsi.so load => pbx_config.so ; List of required codecs load => codec_a_mu.so load => codec_adpcm.so load => codec_alaw.so load => codec_ulaw.so load => codec_gsm.so load => codec_ilbc.so load => codec_lpc10.so ; If you use Dahdi cards for analog lines load => chan_dahdi.so ; Call parking load => res_parking.so ; Below are the modules I needed when setting up call recording ; требуется если используется res_monitor.so load => func_periodic_hook.so ; Required if res_monitor.so is used, the function STRFTIME load => func_strings.so ; Required if res_monitor.so is used to determine the number, function CALLERID load => func_callerid.so ; Required if res_monitor.so is used for MixMonitor load => app_dial.so ; For recording calls load => res_monitor.so ; To support WAV format load => format_wav.so ; For MP3 format support load => format_mp3.so ; To record statistics of calls to MySQL database load => cdr_mysql.so ; To enable SNMP functionality, for example, to collect statistics by various monitoring systems load => res_snmp.so ; To make calls from the context of the placed files to the directory /var/spool/asterisk/outgoing/ load => pbx_spool.so
To apply the changes in the /etc/asterisk/modules.conf file, execute the command from the Asterisk console:
If necessary, you can reboot Asterisk as follows:
sudo service asterisk restart
Here is an example of removing iRedMail.
On the test, delete the installed iRedMail 0.9.7 with Ubuntu Server 16.04 using the uninstall script – clear_iredmail.
Let’s go to the tools directory of the iRedMail installer, save the script in it, in my case it’s:
cd /root/iRedMail-0.9.7/tools/ wget https://ixnfo.com/wp-content/uploads/2017/08/clear_iredmail.zip unzip clear_iredmail.zip
Let’s make it executable:
chmod +x clear_iredmail.sh
The script will remove mysql, ssl, amavisd, clamav, spamassassin, dovecot, postfix, iredapd, users, etc., you need to be careful if there is something else on the server besides iRedMail.
In the script code, you can see the step-by-step process of removing iRedMail.
I received three email messages from one of the servers on Hetzner with information about raids md0, md1, md2:
DegradedArray event on /dev/md/0:example.com
This is an automatically generated mail message from mdadm
running on example.com
A DegradedArray event had been detected on md device /dev/md/0.
Faithfully yours, etc.
P.S. The /proc/mdstat file currently contains the following:
Personalities : [raid6] [raid5] [raid4] [raid1]
md2 : active raid6 sdb3 sdd3
208218112 blocks super 1.0 level 6, 512k chunk, algorithm 2 [4/2] [_U_U]
md1 : active raid1 sdb2 sdd2
524224 blocks super 1.0 [4/2] [_U_U]
md0 : active raid1 sdb1 sdd1
12582784 blocks super 1.0 [4/2] [_U_U]
I looked at the information about RAID and disks:
cat /proc/mdstat cat /proc/partitions mdadm --detail /dev/md0 mdadm --detail /dev/md1 mdadm --detail /dev/md2 fdisk -l | grep '/dev/sd' fdisk -l | less
I was going to send a ticket to the tech support and plan to replace the dropped SSD disks.
SMART recorded information about the dropped discs in the files, there was also their serial number:
smartctl -x /dev/sda > sda.log smartctl -x /dev/sdc > sdc.log
Remove disks from the raid if you can:
mdadm /dev/md0 -r /dev/sda1 mdadm /dev/md1 -r /dev/sda2 mdadm /dev/md2 -r /dev/sda3 mdadm /dev/md0 -r /dev/sdc1 mdadm /dev/md1 -r /dev/sdc2 mdadm /dev/md2 -r /dev/sdc3
If any partition of the disk is displayed as working, and the disk needs to be extracted, then first mark the partition not working and then delete, for example, if /dev/sda1, /dev/sda2 are dropped, and /dev/sda3 works:
mdadm /dev/md0 -f /dev/sda3 mdadm /dev/md0 -r /dev/sda3
In my case, having looked at the information about the dropped discs, I found that they are whole and working, even better than active ones.
I looked at the disk partitions:
fdisk /dev/sda p q fdisk /dev/sdc p q
They were marked the same way as before:
Disk /dev/sda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00015e3f
Device Boot Start End Blocks Id System
/dev/sda1 1 1567 12582912+ fd Linux raid autodetect
/dev/sda2 1567 1633 524288+ fd Linux raid autodetect
/dev/sda3 1633 14594 104109528+ fd Linux raid autodetect
Therefore, after waiting for the synchronization of each returned these discs back to the raid:
mdadm /dev/md0 -a /dev/sda1 mdadm /dev/md1 -a /dev/sda2 mdadm /dev/md2 -a /dev/sda3 mdadm /dev/md0 -a /dev/sdc1 mdadm /dev/md1 -a /dev/sdc2 mdadm /dev/md2 -a /dev/sdc3
At the end, the command cat /proc/mdstat was already displayed with [UUUU].
If the disks are replaced with new ones, then they need to be broken in the same way as the ones installed.
An example of partitioning the disk /dev/sdb is similar to /dev/sda with MBR:
sfdisk -d /dev/sda | sfdisk --force /dev/sdb
Example of partitioning /dev/sdb with GPT and assigning a random UUID disk:
sgdisk -R /dev/sdb /dev/sda sgdisk -G /dev/sdb
Also on the newly installed disk you need to install the bootloader:
grub-install --version grub-install /dev/sdb update-grub
Either through the menu grub (hd0 is /dev/sda, hd0,1 – /dev/sda2):
cat /boot/grub/device.map grub device (hd0) /dev/sda root (hd0,1) setup (hd0) quit
If the grub installation is performed from the rescue disk, you need to look at the partition list and mount it, for example if RAID is not used:
ls /dev/[hsv]d[a-z]*[0-9]* mount /dev/sda3 /mnt
If you are using software RAID:
ls /dev/md* mount /dev/md2 /mnt
ls /dev/mapper/* mount /dev/mapper/vg0-root /mnt
And execute chroot:
chroot-prepare /mnt chroot /mnt
After mounting, you can restore GRUB as I wrote above.
See also my other articles:
How did I make a request to Hetzner to replace the disk in the raid
The solution to the error “md: kicking non-fresh sda1 from array”
The solution to the warning “mismatch_cnt is not 0 on /dev/md*”
mdadm – utility for managing software RAID arrays
Description of RAID types
Diagnostics HDD using smartmontools
Recovering GRUB Linux
It took one day to add a user to Windows 10 from the command line, because nothing happened when the add button was pressed from the control panel.
The first step is to start the command prompt as administrator, for this, in the start menu, type “cmd” or simply find the shortcut “Command line” and click on it with the right mouse button select “Run as administrator “.
At the command prompt, execute the add user command (where NAME is the user name):
net user NAME /add
Finish, the new user can already be seen in the “Control Panel\User Accounts\User Accounts\Account Management“
I will give an example of updating a self-signed certificate on Ubuntu Server with iRedMail installed.
Switch to the root user:Continue reading “How to renew SSL certificate on iRedMail”
After connecting the disk to the server, let’s see a list of all the disks and find the name of the desired one:
sudo fdisk -l
I’ll give an example of mounting NTFS partition of a disk in Ubuntu (since I had a disk partitioned into two partitions, drive C and D, then they were found in the system as /dev/sdb1 and /dev/sdb2, both mounted to the created directories):
sudo mkdir /newhdd1 sudo mount -t ntfs /dev/sdb1 /newhdd1 sudo mkdir /newhdd2 sudo mount -t ntfs /dev/sdb2 /newhdd2
Since before this disk was used in the Windows system, I had a mount error:
The disk contains an unclean file system (0, 0).
Metadata kept in Windows cache, refused to mount.
Failed to mount ‘/dev/sdb1’: The operation is not allowed
The NTFS partition is in an unsafe state. Please resume and shutdown
Windows fully (no hibernation or fast restarting), or mount the volume
read-only with the ‘ro’ mount option.
In this case, you can mount the partition in read-only mode:
sudo mount -t ntfs -o ro /dev/sdb1 /newhdd1
Either fix the partitions with the command:
sudo ntfsfix /dev/sdb1 sudo ntfsfix /dev/sdb2
And after that, mount with full access:
sudo mount -t ntfs /dev/sdb1 /newhdd1 sudo mount -t ntfs /dev/sdb2 /newhdd2
You can unmount it like this:
sudo umount -t ntfs /dev/sdb1 /newhdd1 sudo umount -t ntfs /dev/sdb2 /newhdd2
Let’s review the existing disks:
sudo fdisk -l | grep '/dev/sd'
We display the fdisk menu for further work, for example with the disk /dev/sda:
sudo fdisk /dev/sda
Help can be obtained by pressing the “m” key, exit without saving the changes with the “q” key.
Before mounting, you must create any empty directory:
sudo mkdir /mnt/disk
For example, I connected an external HDD drive for backup copies and mounted with the following command:
sudo mkdir /backup_flows sudo mount -t auto /dev/sdb1 /backup_flows
The /etc/fstab file contains information about all the partitions mounted at boot:
sudo nano /etc/fstab
To learn the UUID of partitions, you can use the command:
You can format the command with:
sudo mkfs.ext4 /dev/sdb1
The table of the file system can be seen by the command:
Mount NTFS partitions on Linux