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How do I trace user activity in Linux?
For currently logged in users, you can always use commands like ps -ef | grep ^nemo to see what commands and processes a user is currently running. To view commands previously run, you can try looking into users’ history files (e.g., .
Can Linux usernames have numbers?
As pointed out in the answers, Linux usernames can be all-numeric. However, this is a Bad Idea as it would confuse many software tools (and human sysadmins!). The useradd and groupadd commands disallow user and group names consisting purely of numeric characters.
What username should I use for Linux?
Usernames must: Start with an alphabetic character. Be 30 characters or fewer for Mac or Linux, or 20 characters or fewer for Windows. Contain only valid Unix Characters – letters, numbers, “-”, “.”, and “_”.
How can I look up a username by id in Linux?
The command id can be used to look up a user’s uid, for example: Is there a command to lookup up a username from a uid? I realize this can be done by looking at the /etc/passwd file but I’m asking if there is an existing command to to this, especially if the user executing it is not root. I’m not looking for the current user’s username, i.e.
How can you tell who owns a file in Unix?
As you know, every file in your Unix OS belongs to some user and some group. It is very easy to confirm the ownership of any file because user id and group id which own the file are always linked to the file. However, sometimes you can’t tell which user owns the file, and today I’m going to explain why.
How to get list of users in Linux?
If we would like to only get a list of the usernames in the system, you can use the awk command or the cut command to filter the output of the other two commands we saw earlier. Any of these will give us a filtered list of users, showing only the very first column which is username:
What to do if numeric ID is shown instead of username?
Simply do an ls command under /home directory and see if any of the directories there appear to have numeric IDs instead of usernames: