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• How to mount a LOFS in Solaris that doesn’t cross mountpoints

  - by jcea

  I need to access my "root" ZFS dataset to delete a file under "/var". But "/var" is overlayed by another ZFS dataset. Since these are system datasets I can't "umount" them while the machine is running. And I want to avoid to reboot the system in "failsafe" mode, since this is a production machine. Teorically ZFS would refuse to mount "/var" dataset over the underlying "/var", because it is not empty. But it works, possibly because they are system datasets mounted early in the boot process. But having the underlying "/var" not empty is preventing me to create an ABE (Alternate Boot Environment), so patching is risky, and I can't upgrade my system using Live Upgrade. The machine is remote. I have an IP KVM, but I rather prefer to avoid booting this machine in "failsafe" mode, if I can. I know there is a file in "/var/" because I can snapshot the "root" dataset and check it. But snapshots are read-only, so I can't get rid of the file. I tried "mkdir /tmp/zzz; mount -F lofs / /tmp/zzz", but when I go to "/tmp/zzz/var", I see the "/var" dataset, not the underlying "root" dataset. That is, the LOFS is crossing mountpoints. I would usually like it, but not this time!. Any suggestion, beside rebooting the machine in "failsafe" and mess with it thru the IP KVM?

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• LVM and cloning HDs

  - by jcea

  Using Linux, I have several backup levels. One of them is a periodical sector by sector copy (using dd) of my laptop harddisk to an external USB disk. Yes, I have other backups too, like remote rsync. This approach (the disk dd) is OK when cloning a HDD with no LVM volumes, since I can plug the external disk anytime and mount the partitions simply mounting /dev/sdb* instead of /dev/sda*. Trivial and handy. Today I moved ALL my harddisk (including the /boot) to LVM. Everything works fine. I will stress it for a couple of days, and then I will do a sector by sector copy to my external harddisk. Now I have a problem, I guess. If in the future I plug the external USB HDD to recover any file, the OS will detect a duplicate LVM configuration, with the same name and the same UUID. Even doing a vgrename (which LVM would be renamed, the internal HDD or the external HDD?), the cloned UUID will not change. Is there any command to change name and UUID? Ideally I would clone the HDD and then change the LVM group name and its UUID, but I don't know how to do it. Another related issue would be... In the past I have booted my laptop using the external disk, using the BIOS boot menu and changing GRUB entries manually to boot from /dev/sdb instead of /dev/sda. But now my current GRUB configuration boots directly from a LVM logical volume, something like: set root='(LVM-root)' in my grub.cfg. So... What is going to happen with duplicated volumes? Any suggestion? I guess I could repartition my external harddisk and change backup strategy from dd to rsync, but this disk has windows installed too, and I really would like to have a physical "real" copy.

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• WEP/WPA/WPA2 and wifi sniffing

  - by jcea

  Hi, I know that WEP traffic can be "sniffed" by any user of the WIFI. I know that WPA/WPA2 traffic is encrypted using a different link key for each user, so they can't sniff traffic... unless they capture the initial handshake. If you are using a PSK (preshared key) schema, then you recover the link key trivially from this initial handshake. If you don't know the PSK, you can capture the handshake and try to crack the PSK by bruteforce offline. Is my understanding correct so far?. I know that WPA2 has AES mode and can use "secure" tokens like X.509 certificates and such, and it is said to be secure against sniffing because capturing the handshake doesn't help you. So, is WPA2+AES secure (so far) against sniffing, and how it actually works?. That is, how is the (random) link key negociated?. When using X.509 certificates or a (private and personal) passphrase. Do WPA/WPA2 have other sniffer-secure modes beside WPA2+AES? How is broadcast traffic managed to be received by all the WIFI users, if each has a different link key?. Thanks in advance! :).

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