The bash history is a log file that contains all commands that the user executed on the Linux shell. When you use the "arrow up" key on our keyboard, then Bash will lookup the previous command from that file and display it on the screen, ready to be executed again.
To get a list of all installed packages on a Debian or Ubuntu server, run the command:
This command will show you a rather long list. To save the list to a file, use this command:
dpkg --get-selections > /tmp/packages.txt
the list is saved then in the file /tmp/packages.txt.
If you seek for a specificy package, use the grep command:
dpkg --get-selections | grep nginx
will show you all packages that contain the word "nginx" in their name.
root@sv1:/# dpkg --get-selections | grep nginx nginx-common install nginx-extras install
The Following command can be used to check and repair all MySQL databases on a Ubuntu or Debian Linux System.
sudo mysqlcheck --defaults-file=/etc/mysql/debian.cnf --auto-repair --optimize --all-databases
mysqlcheck --defaults-file=/etc/mysql/debian.cnf --auto-repair --optimize --all-databases
The benefot of the above comand is that it uses the debian-sys-maint login to MySQL which is available on every Debian and Ubuntu System, so you dont have to provide the MySQL root login details.
1.1 SCP Command Line-An Overview
The SCP command line is commonly used to copy files over SSH, and between popular Operating systems like Linux, Mac and Windows in a secure fashion. SCP is used to copy files to/from a remote server. It also allows you to copy files from one remote server to another remote server, without passing traffic through your PC.
If your mail server stops working (neither incoming nor outgoing email works) and you find the following error message in the mail.log file:
fatal: open database /var/lib/postfix/smtpd_scache.db: File exists
then the smtpd_scache.db might got corrupted. Postfix will recreate this file, if it does not exist. So it can be removed to solve the issue:
rm -f /var/lib/postfix/smtpd_scache.db
Thanks to Alexander Fox for sending me this FAQ.
Dovecot is watching the whole server filesystem for modifications and removed or added sub filesystems. If you get errors similar to this one on your server:
Aug 30 09:10:23 server1 dovecot: master: Warning: /var/www/clients/client1/web1/log is no longer mounted. If this is intentional, remove it with doveadm mount
(the directory path may vary), then you can fix it by excluding the path from being watched by dovecot. In my case, dovecot shall not watch my website directories as they do not contain any mailboxes
Run the following command on the shell as root user:
doveadm mount add '/var/www/*' ignore
To exclude all files and folders in /var/www from deovecot monitoring.
If you get error messages from amavisd similar to the one posted below on a server which is virtualized with OpenVZ:
Mar 5 09:09:02 v100 amavis: (17378-14) (!!)TROUBLE in process_request: Error writing a SMTP response to the socket: Broken pipe at (eval 100) line 987, <GEN44> line 31.
then the issue can be caused by the NUMTCPSOCK value in the openvz limits. Even if the barrier of this limit was never met in /proc/user_beancounters, the above error occurs when more then 25% of all TCP sockets were used. The solution is to set the NUMTCPSOCK barrier and limit to a high value in the openvz container configuration file. Here a value that worked for me on a moderately used mailserver:
Finally restart the OpenVZ VM to apply the new limit value.
If you use the apache mod_security module on your apache server, you might encounter wrong 403 errors for several URL's of the cms systems. Here are some exception rules to avoid that:
For WordPress Blogs
For the ModX CMS
SecRuleRemoveById 300013 300014 300015 300016
SecRuleRemoveById 300013 300016
Add these rules inside the vhost file of the website. If you use ISPConfig to manage the server, then add the rules in the apache directives field of the website settings in ispconfig.
Many thanks to PlanetFox for providing the rules.
The following guide shows how to disable and remove mysql replication from two or more mysql servers. These steps can be used for master/slave and master/master mysql setups. The following SQL commands have to be be executed in phpmyadmin or with the mysql commandline program. It is just important that you are logged in as mysql root user. Below I will use the mysql commandline client.
Login into mysql as root user from commandline:
mysql -u root -p
the mysql command will ask for the mysql root password.
Then execute these commands if the installed mysql version is < 5.5.16:
use the commands below instead if the mysql version is > 5.5.16
RESET SLAVE ALL;
Now edit the my.cnf file (/etc/mysql/my.cnf) and add a # in front of all lines that start with "replicate-" or "master-". Example:
# replicate-same-server-id = 0 # master-host = 192.168.0.105 # master-user = slaveuser # master-password = akst6Wqcz2B # master-connect-retry = 60
Then restart mysql:
The following guide describes the steps to add DNS records that route emails from a domain managed in ISPConfig 3 to google apps / gmail. The guide assumes that you have already setup the dns zone for your domain in ispconfig.
Login to ISPConfig, click on the DNS module icon in the upper navigation bar, then open the settings of the DNS zone that you want to redirect to google and click on the "records" tab. You should see a record list similar to this:
Now Delete the existing MX record and the "mail" A-Record. Then add the following new records:
example.com. ASPMX.L.GOOGLE.COM. 10
example.com. ALT1.ASPMX.L.GOOGLE.COM. 20
example.com. ALT2.ASPMX.L.GOOGLE.COM. 30
example.com. ASPMX2.GOOGLEMAIL.COM. 40
example.com. ASPMX3.GOOGLEMAIL.COM. 50
IMPORTANT: All full domain names like "ghs.google.com." have to end with a dot, if the dot is missing, the name is treated as subdomain of the zone.
The resulting record list should look like this: