I generally put something similar to the following at the beginning of every script (especially if it’ll run as a daemon): #!/bin/bash exec 3>&1 4>&2 trap ‘exec 2>&4 1>&3’ 0 1 2 3 exec 1>log.out 2>&1 # Everything below will go to the file ‘log.out’: Explanation: exec 3>&1 4>&2 Saves file descriptors so they can … Read more
This might sound like a silly idea, but if the users aren’t actually doing anything, you could do: cat /etc/passwd | cut -f 1 -d : >/tmp/users.list Then edit /tmp/users.list to only contain the users you want. Then do: for i in `cat /tmp/users.list` do userdel $i useradd -m $i done However, many Redhat based … Read more
Another option is to use the /proc filesystem. The /proc/net/dev file contains statistics about the configured network interfaces. Each line is dedicated to one network interface and it contains statistics for receive and transmit. The statistics include metrics such total number of received/transmittted bytes, packets, drops, errors and so on. cat /proc/net/dev Inter-| Receive | … Read more
What you have done is only a read speed test. if you are actually copying blocks to another device you have pauses in the reading while the other device is accepting the data you want to write, when this happens you can hit rotational latency issues on the read device (if it’s a hard disk) … Read more
You can use ssh -o StrictHostKeyChecking=no to turn off checking known_hosts momentarily. But I’d advise against this. You should really check why the host key has changed. Another option is to add a specific entry to your ~/.ssh/config for the host in question. This might be valid approach if you have a certain host which … Read more
vmtouch seems like a good tool for the job. Highlights: query how much of a directory is cached query how much of a file is cached (also which pages, graphical representation) load file into cache remove file from cache lock files in cache run as daemon vmtouch manual EDIT: Usage as asked in the question … Read more
On hard disks, throughput and seeking is often faster towards the beginning of the disk, because that data is stored closer to the outer area of the disk, which has more sectors per cylinder. Thus, creating the swap at the beginning of the disk might improve performance. For a 2.6 Linux kernel, there is no … Read more
Based on the date displayed by your version of OpenSSL, it seems you are seeing the full version displayed there. Open SSL 1.0.1 was released on March 14th, 2012. 1.0.1a was released on April 19th of 2012. So, I’m going to go ahead and assert that openssl version -a is the proper, cross-distro way to … Read more
Use -o reconnect,ServerAliveInterval=15,ServerAliveCountMax=3 The combination ServerAliveInterval=15,ServerAliveCountMax=3 causes the I/O errors to pop out after one minute of network outage. This is important but largely undocumented. If ServerAliveInterval option is left at default (so without the alive check), processes which experience I/O hang seem to sleep indefinitely, even after the sshfs gets reconnect‘ed. I regard this … Read more
Right now: Small packet performance sucks under Xen (moved from the question itself to a separate answer instead) According to a user on HN (a KVM developer?) this is due to small packet performance in Xen and also KVM. It’s a known problem with virtualization and according to him, VMWare’s ESX handles this much better. … Read more