If you are preparing for interviews for linux admin jobs you should be familiar with below concepts.
1) Port number of different servers {cat /etc/services}
2) Linux Installation(through FTP,HTTP,NFS)
3) Boot process
4) Diff b/w ext3 and ext2
5) RAID LEVELS and Selection of raid
6) backup methods
7) Package management such as Yum server
8) Kernel Tuning
9) IPTABLES
10) TCP WRAPPERS
11) DIFFERENT RUN LEVELS
12) USER AND GROUP MANAGEMENT
13) QUOTA SETTING(user and group)
14) DIFF B/W CRON AND AT
15) BASIC SHELL SCRIPTING
16) Troubleshooting different issues.
17) Tell me why we should hire you?
18) DAILY ACTIVITES IN YOUR CURRENT COMPANY
19) RECENTLY SOLVED CRITICAL ISSUE
20) LVM (Very Imp)
21) vertias Volume manager
22) cluster basic like HAD , GAB , LLT , HEARTBEAT , CONFIGFILES ,RESOURSE , SERVICE GROUPS etc
23 ) kernel panic troubleshooting
24) Process management
25)Configuration part of NFS , NIS , Samba , DHCP , DNS,Apache, Sendmail etc.
26)Remote administration experience.
And many more depending on your job profile. You should know each topics what you mentioned in your resume . If you are not sure about anything , don’t mention in your resume and your resume should reflect your skills.