rhel & changing network settings

I am not fond of GUIs and enjoy editing configuration files by hand; sure it can be dangerous if you don't know what you're doing - but if you do and don't like GUIs mangling stuff, hand confs are the way to go. Here's how to change RHEL's network conf files - notice the differences between RedHat and Ubuntu.

Edit configuration files stored in /etc/sysconfig/network-scripts/ , /etc/sysconfig & /etc

First, edit network interface card files: 

 * /etc/sysconfig/network-scripts/ifcfg-eth0
 * /etc/sysconfig/network-scripts/ifcfg-eth1 &c.

## Intel Corporation 82573E Gigabit Ethernet Controller (Copper)
DEVICE=eth0
BOOTPROTO=static
DHCPCLASS=
HWADDR=00:30:48:56:A6:2E
IPADDR=192.168.10.3
NETMASK=255.255.255.192
ONBOOT=yes


Edit the file which contains gatway and hostname:

 * /etc/sysconfig/network

## network
NETWORKING=yes
HOSTNAME=super.silly.domain.com
GATEWAY=192.168.10.1


Edit DNS server configuration file:

 * /etc/resolv.conf file:

## resolv.conf
search domain.com silly.domain.com
nameserver 192.168.10.1
nameserver 192.168.10.2
domain domain.com


Restart networking:

# /etc/init.d/network restart

Do a couple tests:

$ ping 192.168.10.1

Output:

PING 192.168.10.1 (192.168.10.1) 56(84) bytes of data.
64 bytes from 192.168.10.1: icmp_seq=1 ttl=251 time=0.972 ms
64 bytes from 192.168.10.1: icmp_seq=2 ttl=251 time=1.11 ms

You can also check for Internet connectivity with nslookup or host command:

$ nslookup not.silly.domain.com
Output:

Server:         192.168.10.1
Address:        192.168.10.1#53

Non-authoritative answer:
Name:   not.silly.domain.com
Address:192.168.10.4

special crontab entries

I have a file I need to change perms on every time my system reboots - just because. While looking for a better way of checking the file's perms through as opposed to doing a perpetual scheduled "for and if" loop, I came across a neat cron (5) stub I'd really never noticed before:

Instead of the first five fields, one of eight special strings may
  appear:

    string         meaning
    ------         -------
    @reboot        Run once, at startup.
    @yearly        Run once a year, "0 0 1 1 *".
    @annually      (same as @yearly)
    @monthly       Run once a month, "0 0 1 * *".
    @weekly        Run once a week, "0 0 * * 0".
    @daily         Run once a day, "0 0 * * *".
    @midnight      (same as @daily)
    @hourly        Run once an hour, "0 * * * *".

Cool. Now all I need to do is have my script run on reboot (well, when cron restarts, but still).