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Showing posts from June, 2012

How do I clean up old large files on Linux?

Many people who have run Linux file servers and ftp servers have at some point wanted to free up some space. One good algorithm to do this efficiently is to remove old data starting with the largest files first. So how to generate such a list? One method is to use a "find -exec du" command:
find /path/to/full/file/system -type f -mtime +10 -exec du -sk {} \; | sort -n > /var/tmp/list_of_files_older_than_10_days_sorted_by_size Once you have that list, you can selectively delete files from the bottom of it. Note that the list will likely be exponentially sorted. That is, the bottom 10% of the list will take up a huge chunk of the used storage space.

How the find the Active Directory Domain Controllers listed in DNS on Linux...

Assumptions:

You have the "host" utility from BIND.You can do a zone transfer from the local DNS serverYour Active Directory admins have properly configured DNS for Active Directory If you have the above, use the following command:
host -t srv -l your.active.directory.dns.domain | grep _kerberos._tcp.*._sites.dc._msdcs.your.active.directory.dns.domain
Replace your.active.directory.dns.domain with your actual AD DNS domain.

On Linux, how do I set the PATH for non-interactive, non-login shells? e.g. for the case of rksh?

Non-interactive, non-login, shells inherit the PATH from the ssh process, so we must set the PATH with ssh. Some shells, like Korn Shell (ksh, rksh, pksh), only parse user environment files in login shells, so there's no way to change the inherited environment in non-interactive, non-login shells.
To set the path globally, build a custom ssh with the needed default path.To set the path for a particular user, first configure ssh to use custom environments by enabling "PermitUserEnvironment" in /etc/ssh/sshd_config: PermitUserEnvironment yes Restart sshdThen set the path in that user's authorized_keys file or using ~/.ssh/environment.Note that you need to set all of the important shell variables. The existence of ~/.ssh/environment seems to preclude the setting of default environmental variable values.So, for example, given a location for binaries for rksh (restricted korn shell), /usr/restricted/bin, place the following in ~/.ssh/environment:HOME=/home/username LOGNAM…