Demonstrations of mountsnoop. mountsnoop traces the mount() and umount syscalls system-wide. For example, running the following series of commands produces this output: # mount --bind /mnt /mnt # umount /mnt # unshare -m # mount --bind /mnt /mnt # umount /mnt # ./mountsnoop.py COMM PID TID MNT_NS CALL mount 710 710 4026531840 mount("/mnt", "/mnt", "", MS_MGC_VAL|MS_BIND, "") = 0 umount 714 714 4026531840 umount("/mnt", 0x0) = 0 unshare 717 717 4026532160 mount("none", "/", "", MS_REC|MS_PRIVATE, "") = 0 mount 725 725 4026532160 mount("/mnt", "/mnt", "", MS_MGC_VAL|MS_BIND, "") = 0 umount 728 728 4026532160 umount("/mnt", 0x0) = 0 # ./mountsnoop.py -P COMM PID TID PCOMM PPID MNT_NS CALL mount 51526 51526 bash 49313 3222937920 mount("/mnt", "/mnt", "", MS_MGC_VAL|MS_BIND, "", "") = 0 umount 51613 51613 bash 49313 3222937920 umount("/mnt", 0x0) = 0 The output shows the calling command, its process ID and thread ID, the mount namespace the call was made in, and the call itself. The mount namespace number is an inode number that uniquely identifies the namespace in the running system. This can also be obtained from readlink /proc/$PID/ns/mnt. Note that because of restrictions in BPF, the string arguments to either syscall may be truncated.