Why would Linux suddenly stop reading /etc/hosts ?

taylorkh · 03-11-2010, 03:00 PM

The subject about says it all. Ubuntu 9.10 64 bit (probably the answer) on a Dell Studio XPS 8000. I have entries in my /etc/hosts for other machines on my LAN.

Quote:

ken@taylor12:~$ cat /etc/hosts
127.0.0.1 localhost
127.0.1.1 taylor12
192.168.0.109 taylor9
192.168.0.110 taylor10
192.168.0.111 taylor11
192.168.0.112 taylor12
192.168.0.113 taylor13wd
192.168.0.123 taylor13wl

All of the sudden I cannot ssh to taylor12wd (wired connection to my netbook) nor taylor13wl (wireless connection to same). Nor can I ping the machine.

Quote:

ken@taylor12:~$ ssh taylor12wl
ssh: connect to host taylor12wl port 22: No route to host

Quote:

PING taylor12wl (208.69.36.132) 56(84) bytes of data.
64 bytes from hit-nxdomain.opendns.com (208.69.36.132): icmp_seq=1 ttl=48 time=77.4 ms

I can connect or ping if I use the IP address and Gnome Commander and Nautilus can connect over ssh! Only the shell does not work.

This is bizarre!

Ken

frieza · 03-11-2010, 03:10 PM

first of all, post the results of 'ifconfig'

no route to host usually meahs that the machine you are trying to talk to is on a different network/subnet then the one you are using, if it wasnt reading the /etc/hosts the error would be
'unknown host' or something like that

just a thought

Skaperen · 03-11-2010, 03:17 PM

First thing is that taylor12wd is not in your /etc/hosts. A typo on your posting?

Second thing is you are getting address resolution OK, but not connection, according to "No route to host". Maybe it's getting an address, but getting the wrong address.

Please provide a copy of the file "/etc/nsswitch.conf" in your next post. For comparison, mine looks like this:

Code:

# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd:         compat
group:          compat
shadow:         compat

hosts:          files dns
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

You may want to open a 2nd window at the same time and run the command:

Code:

tcpdump -nnl -i eth0 -s 1536

to watch the traffic and, in particular, see if the packets are going to the intended IP address, or some other. Watch for the DNS queries (".53" will be appended to addresses) to see if the lookups are going that way. Look for any queries with "AAAA?" in them, indicating an IPv6 lookup happening.

taylorkh · 03-11-2010, 03:52 PM

Thanks frieza,

The machine I am trying to connect to IS on the same network/subnet. I can connect to it with Nautilus and Gnome Commander.
idconfig on taylor12

Quote:

ken@taylor12:~$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:25:64:e8:18:2c
inet addr:192.168.0.112 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::225:64ff:fee8:182c/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1380 errors:0 dropped:0 overruns:0 frame:0
TX packets:1522 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1108078 (1.1 MB) TX bytes:231185 (231.1 KB)
Interrupt:17

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:96 errors:0 dropped:0 overruns:0 frame:0
TX packets:96 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:9651 (9.6 KB) TX bytes:9651 (9.6 KB)

and on the netbook

Quote:

ken@taylor13:~$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:26:b9:10:64:2f
inet addr:192.168.0.113 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::226:b9ff:fe10:642f/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:73 errors:0 dropped:0 overruns:0 frame:0
TX packets:69 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:10934 (10.9 KB) TX bytes:10532 (10.5 KB)
Interrupt:19

eth1 Link encap:Ethernet HWaddr 90:4c:e5:1a:22:70
inet addr:192.168.0.123 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::924c:e5ff:fe1a:2270/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:31 errors:0 dropped:0 overruns:0 frame:0
TX packets:28 errors:6 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:5293 (5.2 KB) TX bytes:6416 (6.4 KB)
Interrupt:17 Base address:0xc000

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:4 errors:0 dropped:0 overruns:0 frame:0
TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:240 (240.0 B) TX bytes:240 (240.0 B)

Yes Skaperen, a typo. Trying to connect to taylor13wl
As requested

Quote:

ken@taylor12:~$ cat /etc/nsswitch.conf
# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd: compat
group: compat
shadow: compat

hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4
networks: files

protocols: db files
services: db files
ethers: db files
rpc: db files

netgroup: nis

I will try the tcpdump if/when it happens again. Had to reboot my desktop - was burning a DVD and apparently the media was bad. Causes the 800 horsepower machine to grind to a complete halt. Of course I can now connect to the netbook.

I have to say that Ubuntu 9.10, at least the 64 bit version, is the sorriest release of Ubuntu I have used and I have used it since 6.04. Lucid Lynx seems better, even in the alphas. When the beta comes out in a week I will be installing it on this Studio XPS and see what it can do. Other than networking and some hardware strangeness, most of my issues are, I think, associated with the restricted nVidia driver. Lucid has the 2.6.32 kernel which has the open source nVidia driver built in as I understand. Also does away with HAL Can't be any worse

Ken