Sysadmin Toolkit

Sysadmin calculators. chmod with 4-digit notation, SUID/SGID/sticky bits, and security warnings. CIDR subnet splitter with IP-in-range check and RFC classification. Cron expression builder with next 10 executions and 12 presets.

#File Permissions

#chmod Calculator

Bidirectional conversion between numeric (0755) and symbolic (rwxr-xr-x) notation. Supports special bits (SUID, SGID, Sticky). Highlights dangerous permissions with security context.

User Group Other
Read
Write
Execute
Special

Equivalent commands









Common permission presets








Octal
Symbolic
Use case































#Networking






#CIDR / Subnet Calculator




Subnet calculator with network/broadcast/range/wildcard mask, host count, RFC classification (private, loopback, link-local, multicast), IP-in-range checker, and subnet splitter.




CIDR / Subnet Calculator


























Quick Reference




/24
254


/25
126


/26
62


/27
30


/28
14


/29
6


/30
2


/31
2 p2p





















#Scheduling






#Cron Expression Builder




Visual cron expression builder with field validation, human-readable translation, next 10 execution preview, and common presets.




Cron Expression Builder









0-59







0-23







1-31







1-12







0-7 (0,7=Sun)











* * * * *




Every minute






Presets








Next 10 Executions








Quick Reference





SymbolMeaningExample




*Any valueEvery minute


*/NEvery N*/5 = every 5


N-MRange1-5 = Mon-Fri


N,MList1,15 = 1st and 15th


N-M/SRange with step1-30/2 = odd days






















#Also See






#Official Resources











#Cyber Aurelien Guidi