pctech at mybellybutton.com
2006-Jun-30 17:10 UTC
[CentOS] /etc/inittab: Serial access/ Console Server
>On Thu, 2006-06-29 at 20:48 -0700, Chris Fox wrote: >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> Rodrigo Barbosa wrote: >> >> > you might want to try agetty: >> > >> > T0:23:respawn:/sbin/agetty 9600 ttyS0 vt100 >> > >> > Not sure if it will work, but seems likely. >> > >> I've always wanted to know how this is done (before serial ports go >> away forever). >> > >We (CentOS Project) just got a $29,000 machine w/o a video card. (Sparc >niagara t2000 machine). > >I use a serial connection to what it boot ... > >You don't just need the inittab setting. You also need a GRUB setting and a secureTTY detting. The following is a paste out of my firewall document that I wrote that has been tested and works: 6.15 Configuring Headless Operation By configuring ?headless? operating we will be able to manage the firewall via a cable plugged into the serial port of the firewall. This obviates the need to plug a keyboard and monitor into it to perform changes. Thus the term ?headless?. 6.15.1 Changes to /etc/inittab The /etc/inittab file contains settings that get applied to the Operating Systems at boot time. There are some changes that need to be made to these settings. In order to edit the /etc/inittab file type: vi /etc/inittab Typing this command will open the /etc/inittab file for editing. As stated earlier the 18th line down is the run level line. Add the following line to the file: S0:12345:respawn:/sbin/agetty ttyS0 9600 linux This line sets the Operating System to be able to send boot time information to the serial port in addition to the console. After you have made these changes to the /etc/inittab file press the colon (: ) key and then type wq to quit vi and save the changes. 6.15.2 Changes to /etc/securetty The /etc/securetty sets the controls for which TTY devices that the root account can log on via. In order for us to be able to log onto the serial console as root or to be able to su to root we must add a line to the file. In order to edit the /etc/secuertty file type: vi /etc/securetty Typing this command will open the /etc/secuertty file for editing. Add the following line to the end of the file: ttyS0 This line sets the Operating System to allow root to log on to the serial port in addition to the console. After you have made these changes to the /etc/securetty file press the colon (: ) key and then type wq to quit vi and save the changes. 6.15.3 Changes to the Boot Loader In order for boot-time messages to be sent to the console, including the boot loader information some changes must be made to the configuration file for it. The boot loader that CentOS uses is GRUB. As such, the configuration file is /etc/grub.conf. The first change that we must make is to add some lines after the timeout line in the GRUB configuration file. In order to edit the /etc/grub.conf file type: vi /etc/grub.conf Typing this command will open the /etc/grub.conf file for editing. Add the following two lines after the timeout line in the configuration file: serial --unit=0 --speed=9600 terminal --timeout=2 serial console Another change that we must make in the GRUB configuration file is to tell the kernel to send out all kernel-level messages to the serial port in addition to the console. That is done by adding the following line to the end of the kernel line: console=tty1 console=ttyS0,9600 After you have made these changes to the /etc/grub.conf file press the colon (: ) key and then type wq to quit vi and save the changes. Once you have made these changes reboot the firewall by typing by typing: reboot The firewall will now reboot. _______________________________________________>CentOS mailing list >CentOS at centos.org >http://lists.centos.org/mailman/listinfo/centos
Very good info...although at my company we manage our AIX and Linux servers with advocent/kvm when ssh is not an option. At home, this may come in handy! Thanks!> -----Original Message----- > From: centos-bounces at centos.org > [mailto:centos-bounces at centos.org] On Behalf Of > pctech at mybellybutton.com > Sent: Friday, June 30, 2006 1:11 PM > To: centos at centos.org > Subject: RE: Re: [CentOS] /etc/inittab: Serial access/ Console Server > > >On Thu, 2006-06-29 at 20:48 -0700, Chris Fox wrote: > >> -----BEGIN PGP SIGNED MESSAGE----- > >> Hash: SHA1 > >> > >> Rodrigo Barbosa wrote: > >> > >> > you might want to try agetty: > >> > > >> > T0:23:respawn:/sbin/agetty 9600 ttyS0 vt100 > >> > > >> > Not sure if it will work, but seems likely. > >> > > >> I've always wanted to know how this is done (before serial > ports go > >> away forever). > >> > > > >We (CentOS Project) just got a $29,000 machine w/o a video > card. (Sparc > >niagara t2000 machine). > > > >I use a serial connection to what it boot ... > > > > > > You don't just need the inittab setting. You also need a > GRUB setting and a secureTTY detting. The following is a > paste out of my firewall document that I wrote that has been > tested and works: > > 6.15 Configuring Headless Operation > By configuring "headless" operating we will be able to manage > the firewall via a cable plugged into the serial port of the > firewall. This obviates the need to plug a keyboard and > monitor into it to perform changes. Thus the term "headless". > > 6.15.1 Changes to /etc/inittab > The /etc/inittab file contains settings that get applied to > the Operating Systems at boot time. There are some changes > that need to be made to these settings. In order to edit the > /etc/inittab file type: > > vi /etc/inittab > > Typing this command will open the /etc/inittab file for editing. > > As stated earlier the 18th line down is the run level line. > Add the following line to the file: > > S0:12345:respawn:/sbin/agetty ttyS0 9600 linux > > This line sets the Operating System to be able to send boot > time information to the serial port in addition to the console. > > After you have made these changes to the /etc/inittab file > press the colon (: ) key and then type wq to quit vi and save > the changes. > > 6.15.2 Changes to /etc/securetty > The /etc/securetty sets the controls for which TTY devices > that the root account can log on via. In order for us to be > able to log onto the serial console as root or to be able to > su to root we must add a line to the file. In order to edit > the /etc/secuertty file type: > > vi /etc/securetty > > Typing this command will open the /etc/secuertty file for editing. > > Add the following line to the end of the file: > > ttyS0 > > This line sets the Operating System to allow root to log on > to the serial port in addition to the console. > > After you have made these changes to the /etc/securetty file > press the colon (: ) key and then type wq to quit vi and save > the changes. > > 6.15.3 Changes to the Boot Loader > In order for boot-time messages to be sent to the console, > including the boot loader information some changes must be > made to the configuration file for it. The boot loader that > CentOS uses is GRUB. As such, the configuration file is > /etc/grub.conf. > > The first change that we must make is to add some lines after > the timeout line in the GRUB configuration file. In order to > edit the /etc/grub.conf file type: > > vi /etc/grub.conf > > Typing this command will open the /etc/grub.conf file for editing. > > Add the following two lines after the timeout line in the > configuration file: > > serial --unit=0 --speed=9600 > terminal --timeout=2 serial console > > Another change that we must make in the GRUB configuration > file is to tell the kernel to send out all kernel-level > messages to the serial port in addition to the console. That > is done by adding the following line to the end of the kernel line: > > console=tty1 console=ttyS0,9600 > > After you have made these changes to the /etc/grub.conf file > press the colon (: ) key and then type wq to quit vi and save > the changes. > > Once you have made these changes reboot the firewall by > typing by typing: > > reboot > > The firewall will now reboot. > > > > _______________________________________________ > >CentOS mailing list > >CentOS at centos.org > >http://lists.centos.org/mailman/listinfo/centos > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos