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Seeing what is being written or read in real time in Linux

Posted by vostorga - 09/11/13 at 09:11:02 pm

Have you ever wondered which processes/tasks write or read to disk in Linux?  Maybe a real time log?

It’s quite simple to enable that feature with the following command:

echo 1 >/proc/sys/vm/block_dump

The output of the command goes to /var/log/messages or /var/log/kernel.log . It depends on the distribution you are using and how your log manager is configured.

Nov  9 21:21:01 hellboy kernel: [140072.428410] bash(31632): READ block 14156776 on md126p4 (8 sectors)
Nov  9 21:21:01 hellboy kernel: [140072.443138] bash(31632): READ block 14156816 on md126p4 (8 sectors)
Nov  9 21:21:57 hellboy kernel: [140127.746763] gnome-shell(5073): WRITE block 120375776 on md126p4 (8 sectors)
Nov  9 21:21:57 hellboy kernel: [140127.765385] gnome-shell(5073): dirtied inode 3627285 (?) on md126p4
Nov  9 21:22:00 hellboy kernel: [140130.602614] nvidia-settings(31743): dirtied inode 689070 (exe) on proc

The output shows the timestamp, the process name, the operation being done (read/write/dirty inode), block or inode number and the device.

Just to take note, a dirty inode is an inode that has had new data written into it but it has not been flushed to disk.

 

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