tcpdump problem

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section1
Posts: 4
Joined: 2008/02/20 00:26:13
Contact:

tcpdump problem

Post by section1 » 2008/03/26 17:04:07

Hello all

I have a problem with tcpdump in a Centos 4.6 box
i get this error:

# tcpdump
Couldn't change to 'pcap' uid=77 gid=77
# ldd /usr/sbin/tcpdump
linux-gate.so.1 => (0xb7fcd000)
libc.so.6 => /lib/tls/i686/libc.so.6 (0xb7eaf000)
/lib/ld-linux.so.2 (0xb7fce000)
# tail -n1 /etc/passwd
pcap:x:77:77::/var/arpwatch:/sbin/nologin

# locate libpcap
.....
/usr/lib/libpcap.so.0
/usr/lib/libpcap.a
/usr/lib/libpcap.so
/usr/lib/libpcap.so.0.8.3
/usr/lib/libpcap.so.0.8
....

kernels 2.6.23.17 recompiled
and 2.6.9-67.0.4.EL default centos kernel


any idea ?
Thanks
section1

section1
Posts: 4
Joined: 2008/02/20 00:26:13
Contact:

Re: tcpdump problem

Post by section1 » 2008/03/26 17:10:03

more info strace output:
....
setgid32(77) = 0
setuid32(77) = -1 EAGAIN (Resource temporarily unavailable)
write(2, "Couldn\'t change to \'pcap\' uid=77"..., 40Couldn't change to 'pcap' uid=77 gid=77) = 40
exit_group(1) = ?

fails the setuid() system call ?
why ?

Thanks

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