Linux Server Tips

Keywords: Linux Server Tips, Linux commands

1 Check last login details, who, when

“w” to check last start up time, currently logged in users

“last” to check logins

“who” Currently logged in users’ details

“lastlog” Users’ last login time

“whoami” Show current username

“finger” Find user information

“id” Current user uid, gid and group information

2 Find ports

netstat -anp | grep 443

lsof -i:443

3 Compile source code

“ar” extract archive, archived installation files

“./configure” configure to fit current systems

“make” compile the source code into binary files e.g. executables

“make install” install the compiled program

4 Linux Directories

“/boot”: Linux kernel, boot configuration etc.

“/bin”: Basic user commands, can be run by users

“/dev”: HDD, Keyboard, Mouse, DVD/CD-ROM device files

“/etc”: Configuration files

“/home”: Users’ working directories (home directory etc.)

“/sbin”: Basic management commands, normally only accessable by administrators

“/usr”: Application, source code files, documents etc.

“/var”: Logs, user mail, process data

“/tmp”: Temporary files

5 Common log files

“/var/log/messages”: Kernel and public messages

“/var/log/cron”: Scheduled Tasks/Crontab

“/var/log/dmesg”: System boot log

“/var/log/maillog”: System mail log

“/var/log/secure”: Access control log

6 Common Linux boot files

“/etc/fstab”: Auto mount on boot

“/etc/initab”: Define default boot level

“/etc/rc.local”: Define custom boot tasks

7 suid, sgid, sticky bit

suid: Run as the owner of the file/binary

sgid: Files created within the folder inherits the folder owner’s permission

sticky bit: Users can only modify, delete wheir own files

8 Check process: “ps”, “top”

9 Check process scheduling: “at”, “crontab”, “batch”, “kill”

10 Extract files

1.*.tarExtract using tar -xvf
2.*.gz Extract using gzip -d OR gunzip
3.*.tar.gz Extract using tar -xzf
4.*.bz2 Extract using bzip2 -d OR bunzip2
5.*.tar.bz2 Extract using tar -xjf
6.*.Z Extract using uncompress
7.*.tar.Z Extract using tar -xZf
8.*.rar Extract using unrar e
9.*.zip Extract using unzip

11 Mounting Windows share

mount -t cifs -o username=windowsusername, password="windowspassword" //ipaddress/folder mnt/linuxtargetfolder

OR

mount.cifs //ipaddress/folder /mnt.linuxtargetfolder -o username="windowsusername", password="windowspassword"