How do I configure GRUB to see all of my memory?
You can specify the amount of memory on your system if your computer is not recognizing all of it. For example if your system says you only have 128 MB of RAM and you know for sure you have 256 MB, then you can specify that in your grub.conf file, located at /boot/grub/grub.conf
What you want to do is add the following syntax mem=M to the kernel line of your grub.conf file. So for instance if you were specifying your system had 256 MB in the grub.conf file, it would look something like this.
splashimage=(hd0,0)/grub/splash.xpm.gz
title Red Hat Enterprise Linux AS (2.4.21-15.EL)
root (hd0,0)
kernel /vmlinuz-2.4.21-15.EL ro root=LABEL=/ mem=256M
initrd /initrd-2.4.21-15.EL.img
title Red Hat Enterprise Linux AS (2.4.21-9.EL)
root (hd0,0)
kernel /vmlinuz-2.4.21-9.EL ro root=LABEL=/ mem=256M
initrd /initrd-2.4.21-9.EL.img
Tags: Configure, GRUB, memory, see
Disable ping requests in Plesk
By default your server can be pinged by anyone, meaning it is discoverable. You can improve security by changing your firewall to only allow known IP addresses to ping your server.
If your static IP is 192.168.1.1 change the rules under Ping Service in Plesk’s default Firewall rules.
Allow incoming from 192.168.1.1
Deny incoming from all others
Tags: Disable, ping, plesk, requests
Using the built-in Plesk firewall
Although you could edit the firewall from the command-line it is much easier using Plesk’s firewall instead.
Just navigate to Modules > Firewall. If you have a static IP address you can create rules so that the server will only allow access from your IP address at your home and/or office.
By default the SSH standard port number is 22. If you look at your logs you might see a large number bad login attempts on that port. Changing this port number is a simple way to make your server more secure. To change the port number login as root and run the following command:
Find the line that says:
Change this line to another port number above 1024. Using a port number above 1024 prevents scans like nmap picking up ssh.
Save the sshd_config file and then restart sshd.
Tags: firewall, plesk
Using SFTP(Secure FTP) in Plesk
Secure FTP is more secure than FTP since it uses the SSH protocol. Shell access must be enabled for each Plesk user for each account.
In the setup page select /bin/bash(chrooted) under the Shell access to server with FTP user’s credentials. This user will now be able to login over SFTP. Remember to change the port in your FTP client. If you are sure you don’t want users to login over standard FTP you can also block this port via the Firewall module in Plesk
The following rules would apply:
Deny incoming from all on ports 21/tcp, 21/udp
You can further secure your FTP server if you have a static IP by allowing access only from that IP. If the static IP is 10.1.1.2 your rules would be:
Allow incoming from 10.1.1.2
Deny incoming from all others
Tags: FTP, plesk, secure, SFTP
How to set the MTU for network interface
The MTU can be set by editing the configuration file for the device. To see the devices you have use the ifconfig command:
$
ifconfig -a
eth0 Link encap:Ethernet HWaddr 08:00:27:7d:bd:61
inet addr:10.0.2.15 Bcast:10.0.2.255 Mask:255.255.255.0
inet6 addr: fe80::a00:27ff:fe7d:bd61/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:153050 errors:54 dropped:0 overruns:0 frame:0
TX packets:86060 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:168036386 (168.0 MB) TX bytes:9165208 (9.1 MB)
Interrupt:10 Base address:0xd020
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:8 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:480 (480.0 B) TX bytes:480 (480.0 B)
Alternatively, you can use the ip command:
$ ip link list
1: lo: mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 08:00:27:7d:bd:61 brd ff:ff:ff:ff:ff:ff
The interface eth0 has an MTU set to 1500 bytes. To change the setting temporarily (to 1200 in this example) issue the following command as root:
ip link set dev eth0 mtu 1200
To make the setting permanent for eth0, edit the configuration file /etc/sysconfig/network-scripts/ifcfg-eth0 and add the line MTU=1200
Tags: interface, MTU, Network, Set
