Questions[strace](server)

If, on Linux, I strace a process, then the reads and writes are shown with the file descriptor handle number. If I look in /proc/$PID/fd I can see the symlinks to the files that correspond to the fd number (if applicable).

Is there anyway to get strace to do this look up for me and (by dereferencing the symlink) show me the filename inside the strace output? It already looks up Linux errno's and truncates & encodes strings, so can it do this too?

Update: I know strace will have shown the open call which shows the path & fd. Which is fine for short running processes. But presume I have a very long running process (measured in days), and did not run the whole thing under strace, merely connect to it later with strace -p.

I'm quite new to strace / netstat / etc. I'm using this command to get a trace of the apache process handling my request (telnet), is there a way to simplify it a bit?

sudo strace -o /tmp/strace -f -s4096 -r -p $(netstat -antlp | \ 
    grep $(lsof -p `pidof telnet` | grep TCP | \
    perl -n -e'/localhost:(\d+)/ && print $1') | grep apache2 | \ 
    perl -n -e'/ESTABLISHED (\d+)/ && print $1')

Thanks!

I run a number of CentOS servers. I was recently doing the occasional yum update but this failed on a handful of the servers. On most I have been able to move forward by doing:

# yum clean all
# rm -f /var/lib/rpm/__db*
# rpm --rebuilddb
# yum update

However on one server, the yum clean command hangs. I have tried running:

# yum -v --noplugins clean all

but I get no output at all. Yum just hangs, and will sit there for hours if I let it, not using any cpu, just stopped. Doing

# strace -f yum -v --noplugins clean all

produces quite a lot of output, but then stops with:

...
stat64("/var/lib/rpm/__db.003", {st_mode=S_IFREG|0644, st_size=450560, ...}) = 0
open("/var/lib/rpm/__db.003", O_RDWR|O_LARGEFILE) = 4
fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0
mmap2(NULL, 450560, PROT_READ|PROT_WRITE, MAP_SHARED, 4, 0) = 0xb6b34000
close(4)                                = 0
stat64("/var/lib/rpm/Packages", {st_mode=S_IFREG|0644, st_size=14938112, ...}) = 0
open("/var/lib/rpm/Packages", O_RDONLY|O_LARGEFILE) = 4
fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0
read(4, "\0\0\0\0\1\0\0\0\0\0\0\0a\25\6\0\10\0\0\0\0\20\0\0\0\10\0\0k\t\0\0"..., 512) = 5
12
close(4)                                = 0
open("/var/lib/rpm/Packages", O_RDONLY|O_LARGEFILE) = 4
fcntl64(4, F_SETFD, FD_CLOEXEC)         = 0
fstat64(4, {st_mode=S_IFREG|0644, st_size=14938112, ...}) = 0
futex(0xb6b7bd1c, FUTEX_WAIT, 1, NULL

At this point I'm feeling stuck. This is a production server, so I don't want to just blow it away, or even blow away all the yum information. Apart from the yum stuff, the server is working fine.

Strangely i can't find it any where but when i stdout the output of strace into afile like this:

strace foo.exe | & tee foo.log

the out put is to short, how can i make the width longer?

Sometimes a process comes and goes faster than I can ps aux, I tried watch -d -n0.1 "ps aux | tail" but again, that's restricted to 1/10th of a second. What I really want is to run a command and follow all new processes, one per line, as they spawn. Even processes that run fast. I know strace has abilities similar to this but I haven't been able to get it to do what I want.

tl;dr : is there a way to log all new processes?

I don't want to know much, no more than a line of ps aux would give me, for the current case I just have a process that's spawned by another and disappears, I want to be able to run it, but I don't know what the command would be. Even knowing new PIDs would be sufficient, since I could figure a script that would take these and run ps | grep on these and give me more info while the process is running (assuming hopefully the process is still around when ps gets going)