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8. Configuring your System
8.a. Filesystem Information
What is fstab?
Under Linux, all partitions used by the system must be listed in
/etc/fstab. This file contains the mount points of those partitions
(where they are seen in the file system structure), how they should be mounted
and with what special options (automatically or not, whether users can mount
them or not, etc.)
/etc/fstab uses a special syntax. Every line consists of six
fields, separated by whitespace (space(s), tabs or a mixture). Each field has
its own meaning:
The first field shows the partition described (the path to the device
The second field shows the mount point at which the partition should be
The third field shows the filesystem used by the partition
The fourth field shows the mount options used by mount when it
wants to mount the partition. As every filesystem has its own mount options,
you are encouraged to read the mount man page (man mount) for a full
listing. Multiple mount options are comma-separated.
The fifth field is used by dump to determine if the partition needs to
be dumped or not. You can generally leave this as 0 (zero).
The sixth field is used by fsck to determine the order in which
filesystems should be checked if the system wasn't shut down properly.
The root filesystem should have 1 while the rest should have 2
(or 0 if a filesystem check isn't necessary).
The default /etc/fstab file provided by Gentoo is not a valid
fstab file. You have to create your own /etc/fstab.
Code Listing 1.1: Opening /etc/fstab
# nano -w /etc/fstab
In the remainder of the text, we use the default /dev/sd* block
device files as partition. You can also opt to use the symbolic links in the
/dev/disk/by-id or /dev/disk/by-uuid. These names are
not likely to change, whereas the default block device files naming depends on
a number of factors (such as how and in what order the disks are attached to
your system). However, if you do not intend to fiddle with the disk ordering,
you can continue with the default block device files safely.
Let us take a look at how we write down the options for the /boot
partition. This is just an example, if you didn't or couldn't create a
/boot, don't copy it.
In our default arm partitioning example, /boot is
usually the /dev/sda1 partition, with ext2 as
filesystem. It needs to be checked during boot, so we would write down:
Code Listing 1.2: An example /boot line for /etc/fstab
/dev/sda1 /boot ext2 defaults 0 2
Some users don't want their /boot partition to be mounted
automatically to improve their system's security. Those people should
substitute defaults with noauto. This does mean that you need to
manually mount this partition every time you want to use it.
Add the rules that match your partitioning scheme and append rules for
your CD-ROM drive(s), and of course, if you have other partitions or drives,
for those too.
Now use the example below to create your /etc/fstab:
auto makes mount guess for the filesystem (recommended for
removable media as they can be created with one of many filesystems) and
user makes it possible for non-root users to mount the CD.
To improve performance, most users would want to add the noatime
mount option, which results in a faster system since access times
aren't registered (you don't need those generally anyway). This is also
recommended for solid state drive (SSD) users, who should also enable
the discard mount option (ext4 and btrfs only for now) which
makes the TRIM command work.
Double-check your /etc/fstab, save and quit to continue.
8.b. Networking Information
Host name, Domainname, etc
One of the choices the user has to make is name his/her PC. This seems to be
quite easy, but lots of users are having difficulties finding the
appropriate name for their Linux-pc. To speed things up, know that any name you
choose can be changed afterwards. For all we care, you can just call your system
tux and domain homenetwork.
Code Listing 2.1: Setting the host name
# nano -w /etc/conf.d/hostname
Second, if you need a domainname, set it in /etc/conf.d/net.
You only need a domain if your ISP or network administrator says so, or if you
have a DNS server but not a DHCP server. You don't need to worry about DNS or
domainnames if your networking is setup for DHCP.
The /etc/conf.d/net file does not exist by default, so you might
need to create it.
Code Listing 2.2: Setting the domainname
# nano -w /etc/conf.d/net
If you choose not to set a domainname, you can get rid of the "This is
hostname.(none)" messages at your login screen by editing
/etc/issue. Just delete the string .\O from that file.
If you have a NIS domain (if you don't know what that is, then you don't have
one), you need to define that one too:
Code Listing 2.3: Setting the NIS domainname
# nano -w /etc/conf.d/net
For more information on configuring DNS and NIS, please read the examples
provided in /usr/share/doc/netifrc-*/net.example.bz2 which
can be read using bzless. Also, you may want to emerge openresolv
to help manage your DNS/NIS setup.
Configuring your Network
Before you get that "Hey, we've had that already"-feeling, you should remember
that the networking you set up in the beginning of the Gentoo installation was
just for the installation. Right now you are going to configure networking for
your Gentoo system permanently.
More detailed information about networking, including advanced topics like
bonding, bridging, 802.1Q VLANs or wireless networking is covered in the Gentoo Network Configuration section.
All networking information is gathered in /etc/conf.d/net. It uses
a straightforward yet not intuitive syntax if you don't know how to set up
networking manually. But don't fear, we'll explain everything. A fully
commented example that covers many different configurations is available in
Let's first install netifrc:
Code Listing 2.4: Installing netifrc
# emerge --noreplace netifrc
DHCP is used by default. For DHCP to work, you will need to install a DHCP
client. This is described later in Installing Necessary System
Tools. Do not forget to install a DHCP client.
If you need to configure your network connection either because you need
specific DHCP options or because you do not use DHCP at all, open
/etc/conf.d/net with your favorite editor (nano is used in
Code Listing 2.5: Opening /etc/conf.d/net for editing
# nano -w /etc/conf.d/net
To enter your own IP address, netmask and gateway, you need
to set both config_eth0 and routes_eth0:
This assumes that your network interface will be called eth0. This is, however,
very system dependent. It is recommended to assume that the interface is named
the same as the interface name when booted from the installation media if
the installation media is sufficiently recent. More information can be found in
Network Interface Naming.
Code Listing 2.6: Manually setting IP information for eth0
config_eth0="192.168.0.2 netmask 255.255.255.0 brd 192.168.0.255"
routes_eth0="default via 192.168.0.1"
To use DHCP, define config_eth0:
Code Listing 2.7: Automatically obtaining an IP address for eth0
Please read /usr/share/doc/netifrc-*/net.example.bz2 for a
list of all available options. Be sure to also read your DHCP client manpage if
you need to set specific DHCP options.
If you have several network interfaces repeat the above steps for
config_eth1, config_eth2, etc.
Now save the configuration and exit to continue.
Automatically Start Networking at Boot
To have your network interfaces activated at boot, you need to add them to the
Code Listing 2.8: Adding net.eth0 to the default runlevel
# cd /etc/init.d
# ln -s net.lo net.eth0
# rc-update add net.eth0 default
If you have several network interfaces, you need to create the appropriate
net.* files just like you did with net.eth0.
If you later find out the assumption about the network interface name (which we
currently document as eth0) was wrong, then
update the /etc/conf.d/net file with the correct interface name (like enp3s0
instead of eth0),
create new symbolic link (like /etc/init.d/net.enp3s0),
remove the old symbolic link (rm /etc/init.d/net.eth0),
add the new one to the default runlevel, and
remove the old one using rc-update del net.eth0 default.
Writing Down Network Information
You now need to inform Linux about your network. This is defined in
/etc/hosts and helps in resolving host names to IP addresses for
hosts that aren't resolved by your nameserver. You need to define your system.
You may also want to define other systems on your network if you don't want to
set up your own internal DNS system.
Code Listing 2.9: Opening /etc/hosts
# nano -w /etc/hosts
Code Listing 2.10: Filling in the networking information
127.0.0.1 tux.homenetwork tux localhost
192.168.0.5 jenny.homenetwork jenny
192.168.0.6 benny.homenetwork benny
Save and exit the editor to continue.
8.c. System Information
First we set the root password by typing:
Code Listing 3.1: Setting the root password
Gentoo uses /etc/rc.conf to configure the services, startup,
and shutdown of your system. Open up /etc/rc.conf and enjoy all
the comments in the file.
Code Listing 3.2: Configuring services
# nano -w /etc/rc.conf
When you're finished configuring these two files, save them and exit.
Gentoo uses /etc/conf.d/keymaps to handle keyboard configuration.
Edit it to configure your keyboard.
Code Listing 3.3: Opening /etc/conf.d/keymaps
# nano -w /etc/conf.d/keymaps
Take special care with the keymap variable. If you select the wrong
keymap, you will get weird results when typing on your keyboard.
When you're finished configuring /etc/conf.d/keymaps, save and
Gentoo uses /etc/conf.d/hwclock to set clock options. Edit it
according to your needs.
Code Listing 3.4: Opening /etc/conf.d/hwclock
# nano -w /etc/conf.d/hwclock
If your hardware clock is not using UTC, you need to add clock="local"
to the file. Otherwise you will notice some clock skew.
When you're finished configuring /etc/conf.d/hwclock, save and
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