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71.
On a default Linux installation, your root UMASK value is 022 - what does it mean?
UMASK is the file creation permissions mask, by having 022 it means that a new file will be created as 644 and a directory with 755.
72.
Where can you find information about your Linux server CPU?
On a Linux system, your server information is kept on /proc/ You can find the CPU information in /proc/cpuinfo.
73.
If you want to trace (attach to) a process and trace its system calls and signals (file/memory access), how can you do it?
In order to attach to a process, you need to find the process number and then attach to it with strace - i.e. strace -p <process_number>
74.
How can you dump the server boot messages into a local log file "myboot.log"?
The boot messages you need to use the dmesg tool and dump it to
myboot.log
dmesg > myboot.log.
75.
Someone is trying to hack your system (valid and invalid users), write a command that will show you failed ssh logins to
the system and its date & ip as "Jul 8 12:00:00 username 192.168.10.10"
You can find the failed logins in the secure log, filter by failed logins, and make a unified line for parsing.
cat /var/log/secure | grep "Failed password for" | sed 's/invalid user//
g' | awk '{ print $1,$2,$3,$9,$11; }'
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