Enabling access over a serial console

To enable access to a (virtual) system over a serial console I'm doing following steps:

1) add a login-prompt on the serial console

echo 'S0:2345:respawn:/sbin/agetty ttyS0 115200 vt100' >> /etc/inittab

2) allow root to login over serial console

echo ttyS0 >> /etc/securetty

3) let /sbin/init reload the inittab to make the login prompt active

/sbin/telinit q

Now you can connect to the serial console and after pressing 'return' you should see a login prompt.

Optionally put the output of the kernel and boot process over the console
4) add parameters console=tty0 console=ttyS0,115200 to the kernel line in /boot/grub/grub.conf

title Red Hat Enterprise Linux AS (2.6.9-78.EL)
root (hd0,0)
kernel /vmlinuz-2.6.9-78.EL ro root=/dev/VolGroup00/LogVol00 console=tty0 console=ttyS0,115200
initrd /initrd-2.6.9-78.EL.img

By adding both parameters console=tty0 and console=ttyS0,115200, the output of the kernel is sent to both consoles. For the boot messages the last console is used. This is useful if your main console is a serial one, but you also have a real (or virtual) monitor connected.

This is what I see when booting one of my virtual systems on Fedora 11:

# virsh start --console rhel4
Domain rhel4 started
Connected to domain rhel4
Escape character is ^]
Linux version 2.6.9-78.EL ([email protected]) (gcc version 3.4.6 20060404 (Red Hat 3.4.6-10)) #1 Wed Jul 9 15:27:01 EDT 2008
BIOS-provided physical RAM map:
BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
BIOS-e820: 000000000009f000 - 00000000000a0000 (reserved)
BIOS-e820: 00000000000e8000 - 0000000000100000 (reserved)
BIOS-e820: 0000000000100000 - 000000001fff0000 (usable)
BIOS-e820: 000000001fff0000 - 0000000020000000 (ACPI data)
BIOS-e820: 00000000fffbc000 - 0000000100000000 (reserved)
0MB HIGHMEM available.
511MB LOWMEM available.
found SMP MP-table at 000fbd10
Using x86 segment limits to approximate NX protection
zapping low mappings.
DMI 2.4 present.
ACPI: PM-Timer IO Port: 0xb008
ACPI: LAPIC (acpi_id[0x00] lapic_id[0x00] enabled)
Processor #0 6:3 APIC version 20
ACPI: LAPIC (acpi_id[0x01] lapic_id[0x01] disabled)
ACPI: LAPIC (acpi_id[0x02] lapic_id[0x02] disabled)
ACPI: LAPIC (acpi_id[0x03] lapic_id[0x03] disabled)
ACPI: LAPIC (acpi_id[0x04] lapic_id[0x04] disabled)
ACPI: LAPIC (acpi_id[0x05] lapic_id[0x05] disabled)
ACPI: LAPIC (acpi_id[0x06] lapic_id[0x06] disabled)
ACPI: LAPIC (acpi_id[0x07] lapic_id[0x07] disabled)
ACPI: LAPIC (acpi_id[0x08] lapic_id[0x08] disabled)
ACPI: LAPIC (acpi_id[0x09] lapic_id[0x09] disabled)
ACPI: LAPIC (acpi_id[0x0a] lapic_id[0x0a] disabled)
ACPI: LAPIC (acpi_id[0x0b] lapic_id[0x0b] disabled)
ACPI: LAPIC (acpi_id[0x0c] lapic_id[0x0c] disabled)
ACPI: LAPIC (acpi_id[0x0d] lapic_id[0x0d] disabled)
ACPI: LAPIC (acpi_id[0x0e] lapic_id[0x0e] disabled)
ACPI: LAPIC (acpi_id[0x0f] lapic_id[0x0f] disabled)
Enabling APIC mode: Flat. Using 0 I/O APICs
ACPI: IOAPIC (id[0x01] address[0xfec00000] gsi_base[0])
IOAPIC[0]: apic_id 1, version 17, address 0xfec00000, GSI 0-23
ACPI: INT_SRC_OVR (bus 0 bus_irq 5 global_irq 5 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 10 global_irq 10 high level)
ACPI: INT_SRC_OVR (bus 0 bus_irq 11 global_irq 11 high level)
Using ACPI (MADT) for SMP configuration information
Allocating PCI resources starting at 30000000 (gap: 20000000:dffbc000)
Built 1 zonelists
Kernel command line: ro root=/dev/VolGroup00/LogVol00 console=tty0 console=ttyS0,115200 elevator=noop
Initializing CPU#0
CPU 0 irqstacks, hard=c0418000 soft=c0417000
PID hash table entries: 2048 (order: 11, 32768 bytes)
Detected 2394.771 MHz processor.
Using pmtmr for high-res timesource
Console: colour VGA+ 80x25
Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)
Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
Memory: 513840k/524224k available (2209k kernel code, 9752k reserved, 745k data, 172k init, 0k highmem)
Calibrating delay using timer specific routine.. 4560.74 BogoMIPS (lpj=2280372)
Security Scaffold v1.0.0 initialized
SELinux: Initializing.
selinux_register_security: Registering secondary module capability
Capability LSM initialized as secondary
Mount-cache hash table entries: 512 (order: 0, 4096 bytes)
CPU: L1 I cache: 32K, L1 D cache: 32K
CPU: L2 cache: 2048K
CPU: Intel Pentium II (Klamath) stepping 03
Enabling fast FPU save and restore... done.
Enabling unmasked SIMD FPU exception support... done.
Checking 'hlt' instruction... OK.
..TIMER: vector=0x31 pin1=0 pin2=-1
checking if image is initramfs... it is
Freeing initrd memory: 1175k freed
NET: Registered protocol family 16
PCI: PCI BIOS revision 2.10 entry at 0xfb510, last bus=0
PCI: Using configuration type 1
mtrr: v2.0 (20020519)
ACPI: Subsystem revision 20040816
ACPI: Interpreter enabled
ACPI: Using IOAPIC for interrupt routing
ACPI: PCI Root Bridge [PCI0] (00:00)
PCI: Probing PCI hardware (bus 00)
ACPI: PCI Interrupt Link [LNKA] (IRQs 5 *10 11)
ACPI: PCI Interrupt Link [LNKB] (IRQs 5 *10 11)
ACPI: PCI Interrupt Link [LNKC] (IRQs 5 10 *11)
ACPI: PCI Interrupt Link [LNKD] (IRQs 5 10 *11)
Linux Plug and Play Support v0.97 (c) Adam Belay
xen_mem: Initialising balloon driver.
usbcore: registered new driver usbfs
usbcore: registered new driver hub
PCI: Using ACPI for IRQ routing
ACPI: PCI Interrupt Link [LNKD] enabled at IRQ 11
ACPI: PCI Interrupt 0000:00:01.2[D] -> GSI 11 (level, high) -> IRQ 11
ACPI: PCI Interrupt Link [LNKA] enabled at IRQ 10
ACPI: PCI Interrupt 0000:00:01.3[A] -> GSI 10 (level, high) -> IRQ 10
ACPI: PCI Interrupt Link [LNKC] enabled at IRQ 11
ACPI: PCI Interrupt 0000:00:03.0[A] -> GSI 11 (level, high) -> IRQ 11
ACPI: PCI Interrupt 0000:00:04.0[A] -> GSI 11 (level, high) -> IRQ 11
ACPI: PCI Interrupt 0000:00:05.0[A] -> GSI 10 (level, high) -> IRQ 10
apm: BIOS version 1.2 Flags 0x03 (Driver version 1.16ac)
apm: overridden by ACPI.
audit: initializing netlink socket (disabled)
audit(1247389170.873:1): initialized
Total HugeTLB memory allocated, 0
VFS: Disk quotas dquot_6.5.1
Dquot-cache hash table entries: 1024 (order 0, 4096 bytes)
Initializing Cryptographic API
ksign: Installing public key data
Loading keyring
- Added public key 9ADA2B4B1EC241DE
- User ID: Red Hat, Inc. (Kernel Module GPG key)
PCI: PIIX3: Enabling Passive Release on 0000:00:01.0
Limiting direct PCI/PCI transfers.
Activating ISA DMA hang workarounds.
pci_hotplug: PCI Hot Plug PCI Core version: 0.5
ACPI: Processor [CPU0] (supports C1)
Real Time Clock Driver v1.12
Linux agpgart interface v0.100 (c) Dave Jones
serio: i8042 AUX port at 0x60,0x64 irq 12
serio: i8042 KBD port at 0x60,0x64 irq 1
Serial: 8250/16550 driver $Revision: 1.90 $ 68 ports, IRQ sharing enabled
�ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
RAMDISK driver initialized: 16 RAM disks of 16384K size 1024 blocksize
Uniform Multi-Platform E-IDE driver Revision: 7.00alpha2
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
PIIX3: IDE controller at PCI slot 0000:00:01.1
PIIX3: chipset revision 0
PIIX3: not 100% native mode: will probe irqs later
ide0: BM-DMA at 0xc000-0xc007, BIOS settings: hda:pio, hdb:pio
ide1: BM-DMA at 0xc008-0xc00f, BIOS settings: hdc:pio, hdd:pio
Using noop io scheduler
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
ide1 at 0x170-0x177,0x376 on irq 15
hda: max request size: 1024KiB
hda: 16777216 sectors (8589 MB) w/256KiB Cache, CHS=16383/255/63, (U)DMA
hda: hda1 hda2
hdc: ATAPI 4X CD-ROM drive, 512kB Cache, (U)DMA
Uniform CD-ROM driver Revision: 3.20
ide-floppy driver 0.99.newide
usbcore: registered new driver hiddev
usbcore: registered new driver usbhid
drivers/usb/input/hid-core.c: v2.0:USB HID core driver
mice: PS/2 mouse device common for all mice
input: AT Translated Set 2 keyboard on isa0060/serio0
input: ImExPS/2 Generic Explorer Mouse on isa0060/serio1
md: md driver 0.90.0 MAX_MD_DEVS=256, MD_SB_DISKS=27
NET: Registered protocol family 2
IP route cache hash table entries: 8192 (order: 3, 32768 bytes)
TCP established hash table entries: 32768 (order: 6, 262144 bytes)
TCP bind hash table entries: 32768 (order: 7, 917504 bytes)
TCP: Hash tables configured (established 32768 bind 32768)
Initializing IPsec netlink socket
NET: Registered protocol family 1
NET: Registered protocol family 17
ACPI wakeup devices:

ACPI: (supports S3 S4 S5)
Freeing unused kernel memory: 172k freed
Red Hat nash version starting
Mounted /proc filesystem
Mounting sysfs
Creating /dev
Starting udev
Loading dm-mod.ko module
device-mapper: 4.5.5-ioctl (2006-12-01) initialised: [email protected]
Loading jbd.ko module
Loading ext3.ko module
Loading dm-mirror.ko module
Loading dm-zero.ko module
Loading dm-snapshot.ko module
Making device-mapper control node
Scanning logical volumes
Reading all physical volumes. This may take a while...
Found volume group "VolGroup00" using metadata type lvm2
Activating logical volumes
2 logical volume(s) in volume group "VolGroup00" now active
Creating root device
Mounting root filesystem
kjournald starting. Commit interval 5 seconds
EXT3-fs: mounted filesystem with ordered data mode.
Switching to new root
INIT: version 2.85 booting
Setting default font (latarcyrheb-sun16): [ OK ]

Welcome to Red Hat Enterprise Linux AS
Press 'I' to enter interactive startup.
Setting clock (utc): Sun Jul 12 09:59:43 BST 2009 [ OK ]
Starting udev: [ OK ]
Initializing hardware... storage network audio done[ OK ]
Configuring kernel parameters: [ OK ]
Loading default keymap (de-latin1): [ OK ]
Setting hostname localhost.localdomain: [ OK ]
Checking root filesystem
[/sbin/fsck.ext3 (1) -- /] fsck.ext3 -a /dev/VolGroup00/LogVol00
/dev/VolGroup00/LogVol00: clean, 64778/897600 files, 397753/1794048 blocks
[ OK ]
Remounting root filesystem in read-write mode: [ OK ]
No RAID disks
Setting up Logical Volume Management: [ OK ]
Checking filesystems
Checking all file systems.
[/sbin/fsck.ext3 (1) -- /boot] fsck.ext3 -a /dev/hda1
/boot: clean, 35/26104 files, 12799/104388 blocks
[ OK ]
Mounting local filesystems: [ OK ]
Enabling local filesystem quotas: [ OK ]
Enabling swap space: [ OK ]
INIT: Entering runlevel: 3
Entering non-interactive startup
Applying Intel Microcode update: [ OK ]
Starting monitoring for VG VolGroup00: [ OK ]
Checking for new hardware [ OK ]
Starting pcmcia: [ OK ]
Setting network parameters: [ OK ]
Bringing up loopback interface: [ OK ]
Bringing up interface eth0: [ OK ]
Bringing up interface eth1:
Determining IP information for eth1... failed.
Starting system logger: [ OK ]
Starting kernel logger: [ OK ]
Starting portmap: [ OK ]
Starting NFS statd: [ OK ]
Starting RPC idmapd: [ OK ]
Mounting other filesystems: [ OK ]
Starting lm_sensors: [ OK ]
Starting automount: No Mountpoints Defined[ OK ]
Starting smartd: [FAILED]
Starting acpi daemon: [ OK ]
Starting cups: [ OK ]
Starting sshd:[ OK ]
Starting xinetd: [ OK ]
Starting sendmail: [ OK ]
Starting sm-client: [ OK ]
Starting console mouse services: [ OK ]
Starting crond: [ OK ]
Starting xfs: [ OK ]
Starting anacron: [ OK ]
[ OK ] atd: [ OK ]
Starting system message bus: [ OK ]
Starting Red Hat Network Daemon: [ OK ]
Starting HAL daemon: [ OK ]

Red Hat Enterprise Linux AS release 4 (Nahant Update 8)
Kernel 2.6.9-78.EL on an i686

localhost.localdomain login:
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