Netcat saves the day!

During a botched upgrade taking an old CentOS box form 5.2 to 5.5, I ended up with a system in such a state that /lib/libselinux.so.1 and /lib64/libselinux.so.1 no longer existed. This is a major problem as it basically stops pretty much every program from working, you can’t even use cp or ls any more!

With yum and RPM unusable, SFTP/SCP/SSH clients and servers out of action and unable to use FTP or wget I thought this box was toast and was going to need a reboot and a live CD to bring it back to life.

After nosying around the system for a while to see what programs I could still run, I discovered that I could still run rsync, but this turned out to be little use as I couldn’t get RSH, SSH or RSYNC network connections in or out of the server.

The last thing I could think of was good old netcat, so I fired it up on another server with a known good copy of libselinux.so.1 and piped /lib64/libselinux.so.1 into it, then with everything crossed I piped it back out on the dying server, and lo and behold it worked and I was able to use ls again!

On the server (source) machine:

cat /lib64/libselinux.so.1 | nc -l 3333

On the client (destination) machine:

nc x.x.x.x 3333 > /lib64/libselinux.so.1

Where x.x.x.x is the IP address of the server.