I am trying to write some custom messages in my dmesg output. I tried:
logger "Hello"
but this does not work. It exits without error, but no "Hello" appears int the output of:
dmesg
I am using a Fedora 9, and it seems that there is no syslogd/klogd daemon running. However, all my kernel messages are succesfully written in the dmesg buffer.
Any idea?
I am making use of the access time to analyse some build process, but it is not working the way I want: the access time is updated the first time I read the file, then it stays the same for a long while, or until the next reboot. For instance:
$ ll -u some_file
-rw-r--r-- 1 root root 1.3M 2010-04-07 10:03 some_file
$ grep abcdef some_file
$ ll -u some_file
-rw-r--r-- 1 root root 1.3M 2010-04-07 11:24 some_file
# The access time is updated
# waiting a few minutes...
$ grep abcdef some_file
$ ll -u some_file
-rw-r--r-- 1 root root 1.3M 2010-04-07 11:24 some_file
# The access time has not been updated :(
I suppose that the file is buffered by Linux in the free memory, the only this copy is accessed the subsequent times for speed reasons. A solution would be to discard the buffers in memory. After searching some forums, I found:
sync
echo 1 > /proc/sys/vm/drop_caches
echo 2 > /proc/sys/vm/drop_caches
echo 3 > /proc/sys/vm/drop_caches
But it is not working, it seems that it only sync up the write buffers, not the read ones. May be it is due to some custom kernel configuration on my distro (fedora 9)?
Or I am missing something here? Is there a way to achieve this access time refresh?
Note also that I do not want to simulate some writes on my entire file tree. Because I am using some makefile based build system, this will cause the entire project to be build again.
I am using a standard ext3 filesystem, without special options.
/dev/sda1 on / type ext3 (rw)
I tried to remount it with strictatime (not recognized) and atime (no difference, I guess it was the default value).
I have a machine with several interfaces that I can configure as I want, for instance:
I would like to forward all the traffic sent to one of these local addresses through the other interface. For instance, all requests to an iperf, ftp, http server at 192.168.1.1 should be not just routed internally, but forwarded through eth2 (and the external network will take care of re-routing the packet to eth1).
I tried and looked at several commands, like iptables, ip route, etc... but nothing worked.
The closest behavior I could get was done with:
ip route change to 192.168.1.1/24 dev eth2
which send all 192.168.1.x on eth2, except for 192.168.1.1 which is still routed internally. May be I could then do NAT forwarding of all traffic directed to fake 192.168.1.2 on eth1, rerouted to 192.168.1.1 internally? I am actually struggling with iptables, but it is too tough for me.
The goal of this setup is to do interface driver testing without using two PCs.
I am using Linux, but if you know how to do that with Windows, I'll buy it!
The external network is just a crossover cable between eth1 and eth2. Let's say I have an http server on my machine. Now I want to access this server from the same machine, but I want to force the TCP/IP traffic to go through this eth1/eth2 cable. How should I configure my interfaces for this?