FAQforge provides answers for frequently asked questions for the Linux-, MAC and Windows operating systems.
Disable quota for a Linux user or group on the shell
Linux user quotas can be edited with the commands edquota or setquota on the shell. While edquota opens the quota settings in a editor like vim, setquota allows you to specify the quota settings on the commandline.
Example for disabling the quota for the user “testuser”:
setquota -u testuser 0 0 0 0 -a
Example for disabling quota for the group “testgroup”:
setquota -g testgroup 0 0 0 0 -a
Convert the charset of file names from iso-8859-15 to utf8
When you copy files from a older Linux or Windows system to a new Linux system, the filenames can get broken and have to be converted. Handy tool to translate the charset of filenames is convmv.
Example
convmv -f iso-8859-15 -t utf8 -r /var/www/myhome.lan/web/images/*
Your Perl version has fleas #37757 #49830
Starting a dry run without changes…
mv “/var/www/var/www/myhome.lan/web/images/gr▒n.jpg” “var/www/myhome.lan/web/images/web/images/grün.jpg”
To finally execute the command (not dry run), use the –notest option:
convmv –notest -f iso-8859-15 -t utf8 -r /var/www/myhome.lan/web/images/*
Thanks to PlanetFox for this FAQ.
Prevent DOS attacks on apache webserver for DEBIAN linux with mod_evasive
The following guide explains the installation of the apache module “mod_evasive”. Mod_evasive tracks the number of requests of files at the apache webserver and blocks the delivery in case that a certain limit has been reached.
Installation
apt-get install libapache2-mod-evasive
Create the log directory for mod_evasive
mkdir -p /var/log/apache2/evasive
chown -R www-data:root /var/log/apache2/evasive
Now we add the configuration for the module at the end of the file /etc/apache2/mods-available/mod-evasive.load
vi /etc/apache2/mods-available/mod-evasive.load
so that it looks like this:
LoadModule evasive20_module /usr/lib/apache2/modules/mod_evasive20.so
DOSHashTableSize 3097
DOSPageCount 2
DOSSiteCount 50
DOSPageInterval 5
DOSSiteInterval 1
DOSBlockingPeriod 10
DOSLogDir “/var/log/apache2/evasive”
and restart apache:
/etc/init.d/apache2 restart
How to change the language of AWStats statistics on Debian Linux (ISPConfig 3)
To change the language of the website statistics generated by AWStats on a Debian Linux server to e.g. german (de), edit the /etc/awstats/awstats.conf file:
nano /etc/awstats/awstats.conf
and change the value of the “Lang” variable. To change the languge to e.g. German, cahnge:
Lang=”auto”
to
Lang=”de”
The website statistics are generated nightly on a ISPConfig 3 server, so it may take up to 24 hours until the statistics will show up in German language.
Thanks to PlaNet Fox for this FAQ.
Change PostgreSQL Locale
wrote by Rafael Marangoni, from Suporte Linux team.
This article explains how to change the default PostgreSQL Locale. Be careful, because we’re considering that you do not have data on postgresql instance.
First, we need to stop the postgres service (if was not already stopped):
/etc/init.d/postgresql stop
Then we need to remove all data files from postgresql data dir. On RedHat based, that’s the dir:
rm -rf /var/lib/pgsql/data/*
Now we change to postgres user:
su postgres
Creating the initial data, selecting the Locale:
initdb –locale=C /var/lib/pgsql/data
or
initdb –locale=pt_BR.UTF-8 /var/lib/pgsql/data
or your locale
/etc/init.d/postgresql stop
Then, we start postgres service:
/etc/init.d/postgresql start
How to enable SSH on VMware ESXi Server
wrote by Rafael Marangoni, from BR Link team.
By default, the ssh login is disabled on VMware ESXi, in opposite way what it happens on VMware ESX Server.
But, there’s a way to enable SSH Login.
After the system is installed, go to the console screen and type:
ALT + F1
After that, a Black screen will appear (be calm, that is normal), then type:
unsupported
Next, the Server will prompt for root password. Then you type the root password.
Afterwards, you’ll have shell access. We need to edit the following file:
vi /etc/inetd.conf
Uncomment the line that starts with “SSH”. Save the file (it’s a normal vi, ZZ will do that for you).
Now reboot the server:
reboot
After it reboots, you should login with SSH on port TCP/22, and user root.
Updating Samba on CentOS 5
wrote by Rafael Marangoni, from Servidor Linux team.
This article explains howto update the Samba packages on CentOS 5 to version 3.5.
First, we need to add a new repository:
cd /etc/yum.repos.d/
wget http://ftp.sernet.de/pub/samba/3.5/centos/5/sernet-samba.repo
Then, update samba:
yum update samba
Probably, you will need winbind too:
yum install samba3-winbind samba3-utils
Check the rpm version:
rpm -qa | grep samba
Restarting Samba:
/etc/init.d/smb restart
Configure PostgreSQL to accept connections from network
wrote by Rafael Marangoni, from Consultoria Linux team.
By default, on some distros, PostgreSQL will only accept connections from localhost. When you have only access from localhost (from localhost Apache, by example) everything is ok, but when you need that postgresql accepts connections for other hosts, you need to make some configs.
First of all, edit the postgresql.conf file (on CentOS the default location is /var/lib/pgsql/data/postgresql.conf).
vi /var/lib/pgsql/data/postgresql.conf
Search the following line:
listen_addresses = ‘localhost’
Change it to:
listen_addresses = ‘*’
Secondly, you need to change the permissions inside pg_hba.conf file (on CentOS, the default location is /var/lib/pgsql/data/pg_hba.conf)
vi /var/lib/pgsql/data/pg_hba.conf
Include the following line (at the end of the file):
host username all 192.168.0.10/32 md5
Where:
username: it’s the name of the postgres user
all: the database name (here we enabled all of them)
192.168.0.10/32: is the IP address/subnet to accept connections
md5: is the method of authentication (md5 requests password)
Reconfigure rkhunter to avoid false positive warnings on Debian 5.0
When you run rkhunter on Debian Linux, you might get a warning when rkhunter is checking for hidden files and directories that some Hiffen files were found in /proc. A closer investigation in rkhunter might bring up the filenames /dev/.static, /dev/.udev and /dev/.initramfs which are normal files on Debian and not related to a attack on your system. The warnings in rkhunter.log are:
[10:21:40] Warning: Hidden directory found: /dev/.static
[10:21:40] Warning: Hidden directory found: /dev/.udev
[10:21:40] Warning: Hidden directory found: /dev/.initramfs
To avoid these warnings, you can reconfigure rkhunter to ignore these files by editing the rkhunter.conf file:
vi /etc/rkhunter.conf
and remove the # in fron of the following lines:
ALLOWHIDDENDIR=/dev/.udev
ALLOWHIDDENDIR=/dev/.static
ALLOWHIDDENDIR=/dev/.initramfs
Create a file of a specific size with random content
Today I tested the logrotation of a Linux server installation and therefore I needed a logfile that was larger then 10 MB. To create such a file of e.g. 11 MB size on the shell, I used this command:
dd if=/dev/urandom of=test.log bs=1M count=11
The content of the file are random characters. If you need a file filled with zeros, use this command:
dd if=/dev/zero of=test.log bs=1M count=11
The result is a file named test.log in the current directory with a size of 11 MB.