I have a VPS,
meowc.at, which was running Ubuntu 10.04. I upgraded to 12.04, but now whenevenr I try to do anything to the filing system, it says "Read-only file system".
However, mount seems to think it is read-write:
$ mount
/dev/xvda1 on / type ext3 (rw,relatime)
proc on /proc type proc (rw,noexec,nosuid)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
as does /proc/mounts: