If you want to determine the name of a Windows machine without DNS, you should try Nbtstat. But that will only work on Windows: For example, NBTSTAT -A 10.10.10.10 On Linux, you should try nmblookup that does nearly the same.
Yes, you can change the attributes of the file to read-only. The command is: chattr +i filename And to disable it: chattr -i filename From man chattr: A file with the i attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file and no data can be … Read more
You are right, the Ubuntu EC2 EBS images don’t come with swap space configured (for 11.04 at least). The “regular” instance-type images do have a swap partition, albeit only 896 MB on the one I tested. If some process blows up and you don’t have swap space, your server could come to a crawling halt … Read more
I use kexec-reboot on nearly all of my production systems. It works incredibly well, allowing me to bypass the long POST time on HP ProLiant servers and reduce the boot cycle from 5 minutes to ~45 seconds. See: https://github.com/error10/kexec-reboot The only caveat is that it doesn’t seem to work on RHEL/CentOS 6.x systems booting UEFI. … Read more
All users: $ getent passwd All groups: $ getent group All groups with a specific user: $ getent group | grep username
(2^16)-1, or 0-65,535 (the -1 is because port 0 is reserved and unavailable). (edited because o_O Tync reminded me that we can’t use port 0, and Steve Folly reminded me that you asked for the highest port, not the number of ports) But you’re probably going about this the wrong way. There are people who … Read more
You are 100% correct. It is not a good practice to free up RAM. This is likely an example of cargo cult system administration.
Schematic: ssh ssh A ——> B ——> C ^ ^ using A’s using B’s ssh key ssh key Preconditions: A is running ssh-agent; A can access B; B can access C; A‘s ssh public key is present in B:~/.ssh/authorized_keys B‘s ssh public key is present in C:~/.ssh/authorized_keys In ~/.ssh/config on A, add Host C ProxyCommand … Read more
The -L flag to rsync will sync the contents of files or directories linked to, rather than the symbolic link.
It’s possible that a process has opened a large file which has since been deleted. You’ll have to kill that process to free up the space. You may be able to identify the process by using lsof. On Linux deleted yet open files are known to lsof and marked as (deleted) in lsof’s output. You … Read more